diff --git a/.dart_tool/package_config.json b/.dart_tool/package_config.json
index fa43a6c8c98..e47664f7334 100644
--- a/.dart_tool/package_config.json
+++ b/.dart_tool/package_config.json
@@ -244,7 +244,7 @@
       "name": "dartdev",
       "rootUri": "../pkg/dartdev",
       "packageUri": "lib/",
-      "languageVersion": "2.6"
+      "languageVersion": "2.12"
     },
     {
       "name": "dartdoc",
diff --git a/pkg/dartdev/bin/dartdev.dart b/pkg/dartdev/bin/dartdev.dart
index c2eee8a0639..7c096eef57c 100644
--- a/pkg/dartdev/bin/dartdev.dart
+++ b/pkg/dartdev/bin/dartdev.dart
@@ -7,6 +7,6 @@ import 'dart:isolate';
 import 'package:dartdev/dartdev.dart';
 
 /// The entry point for dartdev.
-Future<void> main(List<String> args, SendPort port) async {
+Future<void> main(List<String> args, SendPort? port) async {
   await runDartdev(args, port);
 }
diff --git a/pkg/dartdev/lib/dartdev.dart b/pkg/dartdev/lib/dartdev.dart
index f3d60c4cd60..0ad9c9bbb16 100644
--- a/pkg/dartdev/lib/dartdev.dart
+++ b/pkg/dartdev/lib/dartdev.dart
@@ -35,7 +35,7 @@ import 'src/vm_interop_handler.dart';
 
 /// This is typically called from bin/, but given the length of the method and
 /// analytics logic, it has been moved here.
-Future<void> runDartdev(List<String> args, SendPort port) async {
+Future<void> runDartdev(List<String> args, SendPort? port) async {
   VmInteropHandler.initialize(port);
 
   // TODO(sigurdm): Remove when top-level pub is removed.
@@ -61,7 +61,7 @@ Future<void> runDartdev(List<String> args, SendPort port) async {
   // Finally, call the runner to execute the command; see DartdevRunner.
 
   final runner = DartdevRunner(args);
-  var exitCode = 1;
+  int? exitCode = 1;
   try {
     exitCode = await runner.run(args);
   } on UsageException catch (e) {
@@ -86,7 +86,7 @@ class DartdevRunner extends CommandRunner<int> {
 
   final bool verbose;
 
-  Analytics _analytics;
+  late Analytics _analytics;
 
   DartdevRunner(List<String> args)
       : verbose = args.contains('-v') || args.contains('--verbose'),
@@ -221,15 +221,15 @@ class DartdevRunner extends CommandRunner<int> {
 
     // The exit code for the dartdev process; null indicates that it has not been
     // set yet. The value is set in the catch and finally blocks below.
-    int exitCode;
+    int? exitCode;
 
     // Any caught non-UsageExceptions when running the sub command.
-    Object exception;
-    StackTrace stackTrace;
+    Object? exception;
+    StackTrace? stackTrace;
     try {
       exitCode = await super.runCommand(topLevelResults);
 
-      if (path != null && analytics.enabled) {
+      if (analytics.enabled) {
         // Send the event to analytics
         unawaited(
           sendUsageEvent(
@@ -242,7 +242,8 @@ class DartdevRunner extends CommandRunner<int> {
                 // value.
                 //
                 // Note that this will also conflate short-options and long-options.
-                command?.options?.where(command.wasParsed)?.toList(),
+                command?.options.where(command.wasParsed).toList() ??
+                    const <String>[],
             specifiedExperiments: topLevelResults.enabledExperiments,
           ),
         );
@@ -263,7 +264,7 @@ class DartdevRunner extends CommandRunner<int> {
       if (analytics.enabled) {
         unawaited(
           analytics.sendTiming(
-            path ?? '',
+            path,
             stopwatch.elapsedMilliseconds,
             category: 'commands',
           ),
diff --git a/pkg/dartdev/lib/src/analysis_server.dart b/pkg/dartdev/lib/src/analysis_server.dart
index 970d4a8e72f..e8ae5250815 100644
--- a/pkg/dartdev/lib/src/analysis_server.dart
+++ b/pkg/dartdev/lib/src/analysis_server.dart
@@ -14,7 +14,6 @@ import 'package:analysis_server_client/protocol.dart'
         EditBulkFixesResult,
         ResponseDecoder;
 import 'package:args/args.dart';
-import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
 
 import 'core.dart';
@@ -23,7 +22,7 @@ import 'utils.dart';
 
 /// When set, this function is executed just before the Analysis Server starts.
 void Function(String cmdName, List<FileSystemEntity> analysisRoots,
-    ArgResults argResults) preAnalysisServerStart;
+    ArgResults? argResults)? preAnalysisServerStart;
 
 /// A class to provide an API wrapper around an analysis server process.
 class AnalysisServer {
@@ -32,18 +31,18 @@ class AnalysisServer {
     this.sdkPath,
     this.analysisRoots, {
     this.cacheDirectoryPath,
-    @required this.commandName,
-    @required this.argResults,
+    required this.commandName,
+    required this.argResults,
   });
 
-  final String cacheDirectoryPath;
-  final File packagesFile;
+  final String? cacheDirectoryPath;
+  final File? packagesFile;
   final Directory sdkPath;
   final List<FileSystemEntity> analysisRoots;
   final String commandName;
-  final ArgResults argResults;
+  final ArgResults? argResults;
 
-  Process _process;
+  Process? _process;
 
   Completer<bool> _analysisFinished = Completer();
 
@@ -53,8 +52,8 @@ class AnalysisServer {
     // {"event":"server.status","params":{"analysis":{"isAnalyzing":true}}}
     return _streamController('server.status')
         .stream
-        .where((event) => event['analysis'] != null)
-        .map((event) => event['analysis']['isAnalyzing'] as bool);
+        .where((event) => event!['analysis'] != null)
+        .map((event) => (event!['analysis']['isAnalyzing']!) as bool);
   }
 
   /// This future completes when we next receive an analysis finished event
@@ -65,7 +64,7 @@ class AnalysisServer {
   Stream<FileAnalysisErrors> get onErrors {
     // {"event":"analysis.errors","params":{"file":"/Users/.../lib/main.dart","errors":[]}}
     return _streamController('analysis.errors').stream.map((event) {
-      final file = event['file'] as String;
+      final file = event!['file'] as String;
       final errorsList = event['errors'] as List<dynamic>;
       final errors = errorsList
           .map<Map<String, dynamic>>(castStringKeyedMap)
@@ -76,7 +75,7 @@ class AnalysisServer {
     });
   }
 
-  Future<int> get onExit => _process.exitCode;
+  Future<int> get onExit => _process!.exitCode;
 
   final Map<String, StreamController<Map<String, dynamic>>> _streamControllers =
       {};
@@ -94,19 +93,19 @@ class AnalysisServer {
       '--sdk',
       sdkPath.path,
       if (cacheDirectoryPath != null) '--cache=$cacheDirectoryPath',
-      if (packagesFile != null) '--packages=${packagesFile.path}',
+      if (packagesFile != null) '--packages=${packagesFile!.path}',
     ];
 
     _process = await startDartProcess(sdk, command);
     // This callback hookup can't throw.
-    _process.exitCode.whenComplete(() => _process = null);
+    _process!.exitCode.whenComplete(() => _process = null);
 
-    final Stream<String> errorStream = _process.stderr
+    final Stream<String> errorStream = _process!.stderr
         .transform<String>(utf8.decoder)
         .transform<String>(const LineSplitter());
     errorStream.listen(log.stderr);
 
-    final Stream<String> inStream = _process.stdout
+    final Stream<String> inStream = _process!.stdout
         .transform<String>(utf8.decoder)
         .transform<String>(const LineSplitter());
     inStream.listen(_handleServerResponse);
@@ -125,7 +124,7 @@ class AnalysisServer {
     // be passed to the analysis server.
     List<String> analysisRootPaths = analysisRoots.map((root) {
       return trimEnd(
-          root.absolute.resolveSymbolicLinksSync(), path.context.separator);
+          root.absolute.resolveSymbolicLinksSync(), path.context.separator)!;
     }).toList();
 
     onAnalyzing.listen((bool isAnalyzing) {
@@ -178,7 +177,7 @@ class AnalysisServer {
   }
 
   Future<Map<String, dynamic>> _sendCommand(String method,
-      {Map<String, dynamic> params}) {
+      {Map<String, dynamic>? params}) {
     final String id = (++_id).toString();
     final String message = json.encode(<String, dynamic>{
       'id': id,
@@ -187,11 +186,11 @@ class AnalysisServer {
     });
 
     _requestCompleters[id] = Completer();
-    _process.stdin.writeln(message);
+    _process!.stdin.writeln(message);
 
     log.trace('==> $message');
 
-    return _requestCompleters[id].future;
+    return _requestCompleters[id]!.future;
   }
 
   void _handleServerResponse(String line) {
@@ -216,27 +215,28 @@ class AnalysisServer {
               .remove(id)
               ?.completeError(RequestError.parse(error));
         } else {
-          _requestCompleters.remove(id)?.complete(response['result']);
+          _requestCompleters.remove(id)?.complete(response['result'] ?? {});
         }
       }
     }
   }
 
-  void _handleServerError(Map<String, dynamic> error) {
+  void _handleServerError(Map<String, dynamic>? error) {
+    final err = error!;
     // Fields are 'isFatal', 'message', and 'stackTrace'.
-    log.stderr('Error from the analysis server: ${error['message']}');
-    if (error['stackTrace'] != null) {
-      log.stderr(error['stackTrace'] as String);
+    log.stderr('Error from the analysis server: ${err['message']}');
+    if (err['stackTrace'] != null) {
+      log.stderr(err['stackTrace'] as String);
     }
   }
 
-  StreamController<Map<String, dynamic>> _streamController(String streamId) {
+  StreamController<Map<String, dynamic>?> _streamController(String streamId) {
     return _streamControllers.putIfAbsent(
         streamId, () => StreamController<Map<String, dynamic>>.broadcast());
   }
 
   Future<bool> dispose() async {
-    return _process?.kill();
+    return _process?.kill() ?? true;
   }
 }
 
@@ -262,10 +262,10 @@ class AnalysisError implements Comparable<AnalysisError> {
   // },"message":"...","hasFix":false}
   Map<String, dynamic> json;
 
-  String get severity => json['severity'] as String;
+  String? get severity => json['severity'] as String?;
 
   _AnalysisSeverity get _severityLevel =>
-      _severityMap[severity] ?? _AnalysisSeverity.none;
+      _severityMap[severity!] ?? _AnalysisSeverity.none;
 
   bool get isInfo => _severityLevel == _AnalysisSeverity.info;
 
@@ -279,26 +279,26 @@ class AnalysisError implements Comparable<AnalysisError> {
 
   String get code => json['code'] as String;
 
-  String get correction => json['correction'] as String;
+  String? get correction => json['correction'] as String?;
 
-  int get endColumn => json['location']['endColumn'] as int;
+  int? get endColumn => json['location']['endColumn'] as int?;
 
-  int get endLine => json['location']['endLine'] as int;
+  int? get endLine => json['location']['endLine'] as int?;
 
   String get file => json['location']['file'] as String;
 
-  int get startLine => json['location']['startLine'] as int;
+  int? get startLine => json['location']['startLine'] as int?;
 
-  int get startColumn => json['location']['startColumn'] as int;
+  int? get startColumn => json['location']['startColumn'] as int?;
 
   int get offset => json['location']['offset'] as int;
 
   int get length => json['location']['length'] as int;
 
-  String get url => json['url'] as String;
+  String? get url => json['url'] as String?;
 
   List<DiagnosticMessage> get contextMessages {
-    var messages = json['contextMessages'] as List<dynamic>;
+    var messages = json['contextMessages'] as List<dynamic>?;
     if (messages == null) {
       // The field is optional, so we return an empty list as a default value.
       return [];
@@ -326,7 +326,7 @@ class AnalysisError implements Comparable<AnalysisError> {
   }
 
   @override
-  String toString() => '${severity.toLowerCase()} • '
+  String toString() => '${severity!.toLowerCase()} • '
       '$message • $file:$startLine:$startColumn • '
       '($code)';
 }
@@ -336,11 +336,11 @@ class DiagnosticMessage {
 
   DiagnosticMessage(this.json);
 
-  int get column => json['location']['startColumn'] as int;
+  int? get column => json['location']['startColumn'] as int?;
 
-  int get endColumn => json['location']['endColumn'] as int;
+  int? get endColumn => json['location']['endColumn'] as int?;
 
-  int get endLine => json['location']['endLine'] as int;
+  int? get endLine => json['location']['endLine'] as int?;
 
   String get filePath => json['location']['file'] as String;
 
@@ -373,7 +373,7 @@ class RequestError {
   final String message;
   final String stackTrace;
 
-  RequestError(this.code, this.message, {this.stackTrace});
+  RequestError(this.code, this.message, {required this.stackTrace});
 
   @override
   String toString() => '[RequestError code: $code, message: $message]';
diff --git a/pkg/dartdev/lib/src/analytics.dart b/pkg/dartdev/lib/src/analytics.dart
index 3072c34d3a5..7b69d8e88a2 100644
--- a/pkg/dartdev/lib/src/analytics.dart
+++ b/pkg/dartdev/lib/src/analytics.dart
@@ -101,7 +101,7 @@ Analytics createAnalyticsInstance(bool disableAnalytics) {
 ///
 /// This can return null under some conditions, including when the user's home
 /// directory does not exist.
-Directory getDartStorageDirectory() {
+Directory? getDartStorageDirectory() {
   var homeDir = Directory(userHomeDir());
   if (!homeDir.existsSync()) {
     return null;
@@ -133,11 +133,11 @@ class DartdevAnalytics extends AnalyticsImpl {
     }
 
     // If there's no explicit setting (enabled or disabled) then we don't send.
-    return (properties['enabled'] as bool) ?? false;
+    return (properties['enabled'] as bool?) ?? false;
   }
 
   bool get disclosureShownOnTerminal =>
-      (properties['disclosureShown'] as bool) ?? false;
+      (properties['disclosureShown'] as bool?) ?? false;
 
   set disclosureShownOnTerminal(bool value) {
     properties['disclosureShown'] = value;
@@ -171,7 +171,7 @@ class _LoggingAnalytics extends AnalyticsMock {
   bool get firstRun => false;
 
   @override
-  Future sendScreenView(String viewName, {Map<String, String> parameters}) {
+  Future sendScreenView(String viewName, {Map<String, String>? parameters}) {
     parameters ??= <String, String>{};
     parameters['viewName'] = viewName;
     return _log('screenView', parameters);
@@ -179,7 +179,7 @@ class _LoggingAnalytics extends AnalyticsMock {
 
   @override
   Future sendEvent(String category, String action,
-      {String label, int value, Map<String, String> parameters}) {
+      {String? label, int? value, Map<String, String>? parameters}) {
     parameters ??= <String, String>{};
     return _log(
         'event',
@@ -193,7 +193,7 @@ class _LoggingAnalytics extends AnalyticsMock {
 
   @override
   Future sendTiming(String variableName, int time,
-      {String category, String label}) {
+      {String? category, String? label}) {
     return _log('timing', {
       'variableName': variableName,
       'time': time,
diff --git a/pkg/dartdev/lib/src/commands/analyze.dart b/pkg/dartdev/lib/src/commands/analyze.dart
index 2c8837b7a9a..1112fe8056b 100644
--- a/pkg/dartdev/lib/src/commands/analyze.dart
+++ b/pkg/dartdev/lib/src/commands/analyze.dart
@@ -82,12 +82,13 @@ class AnalyzeCommand extends DartdevCommand {
 
   @override
   FutureOr<int> run() async {
+    final args = argResults!;
     // Find targets from the 'rest' params.
     final List<io.FileSystemEntity> targets = [];
-    if (argResults.rest.isEmpty) {
+    if (args.rest.isEmpty) {
       targets.add(io.Directory.current);
     } else {
-      for (String targetPath in argResults.rest) {
+      for (String targetPath in args.rest) {
         if (io.Directory(targetPath).existsSync()) {
           targets.add(io.Directory(targetPath));
         } else if (io.File(targetPath).existsSync()) {
@@ -100,8 +101,8 @@ class AnalyzeCommand extends DartdevCommand {
 
     final List<AnalysisError> errors = <AnalysisError>[];
 
-    final machineFormat = argResults['format'] == 'machine';
-    final jsonFormat = argResults['format'] == 'json';
+    final machineFormat = args['format'] == 'machine';
+    final jsonFormat = args['format'] == 'json';
 
     final targetsNames =
         targets.map((entity) => path.basename(entity.path)).join(', ');
@@ -113,9 +114,9 @@ class AnalyzeCommand extends DartdevCommand {
       _packagesFile(),
       io.Directory(sdk.sdkPath),
       targets,
-      cacheDirectoryPath: argResults['cache'],
+      cacheDirectoryPath: args['cache'],
       commandName: 'analyze',
-      argResults: argResults,
+      argResults: args,
     );
 
     server.onErrors.listen((FileAnalysisErrors fileErrors) {
@@ -160,7 +161,9 @@ class AnalyzeCommand extends DartdevCommand {
       emitDefaultFormat(
         log,
         errors,
-        relativeToDir: relativeTo is io.File ? relativeTo.parent : relativeTo,
+        relativeToDir: relativeTo is io.File
+            ? relativeTo.parent
+            : relativeTo as io.Directory?,
         verbose: verbose,
       );
     }
@@ -181,8 +184,8 @@ class AnalyzeCommand extends DartdevCommand {
       return 3;
     }
 
-    bool fatalWarnings = argResults['fatal-warnings'];
-    bool fatalInfos = argResults['fatal-infos'];
+    bool fatalWarnings = args['fatal-warnings'];
+    bool fatalInfos = args['fatal-infos'];
 
     if (fatalWarnings && hasWarnings) {
       return 2;
@@ -193,8 +196,8 @@ class AnalyzeCommand extends DartdevCommand {
     }
   }
 
-  io.File _packagesFile() {
-    var path = argResults['packages'];
+  io.File? _packagesFile() {
+    var path = argResults!['packages'];
     if (path is String) {
       var file = io.File(path);
       if (!file.existsSync()) {
@@ -210,7 +213,7 @@ class AnalyzeCommand extends DartdevCommand {
   static void emitDefaultFormat(
     Logger log,
     List<AnalysisError> errors, {
-    io.Directory relativeToDir,
+    io.Directory? relativeToDir,
     bool verbose = false,
   }) {
     final ansi = log.ansi;
@@ -220,10 +223,10 @@ class AnalyzeCommand extends DartdevCommand {
 
     final wrapWidth = dartdevUsageLineLength == null
         ? null
-        : (dartdevUsageLineLength - _bodyIndentWidth);
+        : (dartdevUsageLineLength! - _bodyIndentWidth);
 
     for (final AnalysisError error in errors) {
-      var severity = error.severity.toLowerCase().padLeft(_severityWidth);
+      var severity = error.severity!.toLowerCase().padLeft(_severityWidth);
       if (error.isError) {
         severity = ansi.error(severity);
       }
@@ -231,7 +234,7 @@ class AnalyzeCommand extends DartdevCommand {
       var codeRef = error.code;
       // If we're in verbose mode, write any error urls instead of error codes.
       if (error.url != null && verbose) {
-        codeRef = error.url;
+        codeRef = error.url!;
       }
 
       // Emit "file:line:col * Error message. Correction (code)."
@@ -278,7 +281,7 @@ class AnalyzeCommand extends DartdevCommand {
           'range': range,
         };
 
-    Map<String, dynamic> position(int offset, int line, int column) => {
+    Map<String, dynamic> position(int? offset, int? line, int? column) => {
           'offset': offset,
           'line': line,
           'column': column,
@@ -364,8 +367,8 @@ class AnalyzeCommand extends DartdevCommand {
   }
 
   /// Return a relative path if it is a shorter reference than the given dir.
-  static String _relativePath(String givenPath, io.Directory fromDir) {
-    String fromPath = fromDir?.absolute?.resolveSymbolicLinksSync();
+  static String _relativePath(String givenPath, io.Directory? fromDir) {
+    String? fromPath = fromDir?.absolute.resolveSymbolicLinksSync();
     String relative = path.relative(givenPath, from: fromPath);
     return relative.length <= givenPath.length ? relative : givenPath;
   }
diff --git a/pkg/dartdev/lib/src/commands/compile.dart b/pkg/dartdev/lib/src/commands/compile.dart
index bd487137cc3..6e3d600a720 100644
--- a/pkg/dartdev/lib/src/commands/compile.dart
+++ b/pkg/dartdev/lib/src/commands/compile.dart
@@ -21,14 +21,14 @@ const int compileErrorExitCode = 64;
 class Option {
   final String flag;
   final String help;
-  final String abbr;
-  final String defaultsTo;
-  final List<String> allowed;
-  final Map<String, String> allowedHelp;
+  final String? abbr;
+  final String? defaultsTo;
+  final List<String>? allowed;
+  final Map<String, String>? allowedHelp;
 
   Option(
-      {this.flag,
-      this.help,
+      {required this.flag,
+      required this.help,
       this.abbr,
       this.defaultsTo,
       this.allowed,
@@ -71,7 +71,7 @@ class CompileJSCommand extends CompileSubcommandCommand {
   @override
   final ArgParser argParser = ArgParser.allowAnything();
 
-  CompileJSCommand({bool verbose})
+  CompileJSCommand({bool verbose = false})
       : super(cmdName, 'Compile Dart to JavaScript.', verbose);
 
   @override
@@ -91,7 +91,7 @@ class CompileJSCommand extends CompileSubcommandCommand {
           '--libraries-spec=$librariesPath',
           '--cfe-invocation-modes=compile',
           '--invoker=dart_cli',
-          ...argResults.arguments,
+          ...argResults!.arguments,
         ],
         packageConfigOverride: null);
 
@@ -109,25 +109,25 @@ class CompileSnapshotCommand extends CompileSubcommandCommand {
   final String formatName;
 
   CompileSnapshotCommand({
-    this.commandName,
-    this.help,
-    this.fileExt,
-    this.formatName,
-    bool verbose,
+    required this.commandName,
+    required this.help,
+    required this.fileExt,
+    required this.formatName,
+    bool verbose = false,
   }) : super(commandName, 'Compile Dart $help', verbose) {
     argParser
       ..addOption(
-        commonOptions['outputFile'].flag,
-        help: commonOptions['outputFile'].help,
-        abbr: commonOptions['outputFile'].abbr,
+        commonOptions['outputFile']!.flag,
+        help: commonOptions['outputFile']!.help,
+        abbr: commonOptions['outputFile']!.abbr,
       )
       ..addOption(
-        commonOptions['verbosity'].flag,
-        help: commonOptions['verbosity'].help,
-        abbr: commonOptions['verbosity'].abbr,
-        defaultsTo: commonOptions['verbosity'].defaultsTo,
-        allowed: commonOptions['verbosity'].allowed,
-        allowedHelp: commonOptions['verbosity'].allowedHelp,
+        commonOptions['verbosity']!.flag,
+        help: commonOptions['verbosity']!.help,
+        abbr: commonOptions['verbosity']!.abbr,
+        defaultsTo: commonOptions['verbosity']!.defaultsTo,
+        allowed: commonOptions['verbosity']!.allowed,
+        allowedHelp: commonOptions['verbosity']!.allowedHelp,
       );
 
     addExperimentalFlags(argParser, verbose);
@@ -146,20 +146,21 @@ class CompileSnapshotCommand extends CompileSubcommandCommand {
 
   @override
   FutureOr<int> run() async {
-    if (argResults.rest.isEmpty) {
+    final args = argResults!;
+    if (args.rest.isEmpty) {
       // This throws.
       usageException('Missing Dart entry point.');
-    } else if (!isJitSnapshot && argResults.rest.length > 1) {
+    } else if (!isJitSnapshot && args.rest.length > 1) {
       usageException('Unexpected arguments after Dart entry point.');
     }
 
-    final String sourcePath = argResults.rest[0];
+    final String sourcePath = args.rest[0];
     if (!checkFile(sourcePath)) {
       return -1;
     }
 
     // Determine output file name.
-    String outputFile = argResults[commonOptions['outputFile'].flag];
+    String? outputFile = args[commonOptions['outputFile']!.flag];
     if (outputFile == null) {
       final inputWithoutDart = sourcePath.endsWith('.dart')
           ? sourcePath.substring(0, sourcePath.length - 5)
@@ -167,31 +168,31 @@ class CompileSnapshotCommand extends CompileSubcommandCommand {
       outputFile = '$inputWithoutDart.$fileExt';
     }
 
-    final enabledExperiments = argResults.enabledExperiments;
+    final enabledExperiments = args.enabledExperiments;
     // Build arguments.
-    List<String> args = [];
-    args.add('--snapshot-kind=$formatName');
-    args.add('--snapshot=${path.canonicalize(outputFile)}');
+    List<String> buildArgs = [];
+    buildArgs.add('--snapshot-kind=$formatName');
+    buildArgs.add('--snapshot=${path.canonicalize(outputFile)}');
 
-    String verbosity = argResults[commonOptions['verbosity'].flag];
-    args.add('--verbosity=$verbosity');
+    String? verbosity = args[commonOptions['verbosity']!.flag];
+    buildArgs.add('--verbosity=$verbosity');
 
     if (enabledExperiments.isNotEmpty) {
-      args.add("--enable-experiment=${enabledExperiments.join(',')}");
+      buildArgs.add("--enable-experiment=${enabledExperiments.join(',')}");
     }
     if (verbose) {
-      args.add('-v');
+      buildArgs.add('-v');
     }
-    args.add(path.canonicalize(sourcePath));
+    buildArgs.add(path.canonicalize(sourcePath));
 
     // Add the training arguments.
-    if (argResults.rest.length > 1) {
-      args.addAll(argResults.rest.sublist(1));
+    if (args.rest.length > 1) {
+      buildArgs.addAll(args.rest.sublist(1));
     }
 
     log.stdout('Compiling $sourcePath to $commandName file $outputFile.');
     // TODO(bkonyi): perform compilation in same process.
-    final process = await startDartProcess(sdk, args);
+    final process = await startDartProcess(sdk, buildArgs);
     routeToStdout(process);
     return process.exitCode;
   }
@@ -206,24 +207,24 @@ class CompileNativeCommand extends CompileSubcommandCommand {
   final String help;
 
   CompileNativeCommand({
-    this.commandName,
-    this.format,
-    this.help,
-    bool verbose,
+    required this.commandName,
+    required this.format,
+    required this.help,
+    bool verbose = false,
   }) : super(commandName, 'Compile Dart $help', verbose) {
     argParser
       ..addOption(
-        commonOptions['outputFile'].flag,
-        help: commonOptions['outputFile'].help,
-        abbr: commonOptions['outputFile'].abbr,
+        commonOptions['outputFile']!.flag,
+        help: commonOptions['outputFile']!.help,
+        abbr: commonOptions['outputFile']!.abbr,
       )
       ..addOption(
-        commonOptions['verbosity'].flag,
-        help: commonOptions['verbosity'].help,
-        abbr: commonOptions['verbosity'].abbr,
-        defaultsTo: commonOptions['verbosity'].defaultsTo,
-        allowed: commonOptions['verbosity'].allowed,
-        allowedHelp: commonOptions['verbosity'].allowedHelp,
+        commonOptions['verbosity']!.flag,
+        help: commonOptions['verbosity']!.help,
+        abbr: commonOptions['verbosity']!.abbr,
+        defaultsTo: commonOptions['verbosity']!.defaultsTo,
+        allowed: commonOptions['verbosity']!.allowed,
+        allowedHelp: commonOptions['verbosity']!.allowedHelp,
       )
       ..addMultiOption('define', abbr: 'D', valueHelp: 'key=value', help: '''
 Define an environment declaration. To specify multiple declarations, use multiple options or use commas to separate key-value pairs.
@@ -269,13 +270,14 @@ Remove debugging information from the output and save it separately to the speci
           "'dart compile $format' is not supported on x86 architectures");
       return 64;
     }
+    final args = argResults!;
+
     // We expect a single rest argument; the dart entry point.
-    if (argResults.rest.length != 1) {
+    if (args.rest.length != 1) {
       // This throws.
       usageException('Missing Dart entry point.');
     }
-
-    final String sourcePath = argResults.rest[0];
+    final String sourcePath = args.rest[0];
     if (!checkFile(sourcePath)) {
       return -1;
     }
@@ -284,16 +286,16 @@ Remove debugging information from the output and save it separately to the speci
       await generateNative(
         kind: format,
         sourceFile: sourcePath,
-        outputFile: argResults['output'],
-        defines: argResults['define'],
-        packages: argResults['packages'],
-        enableAsserts: argResults['enable-asserts'],
-        enableExperiment: argResults.enabledExperiments.join(','),
-        soundNullSafety: argResults['sound-null-safety'],
-        debugFile: argResults['save-debugging-info'],
+        outputFile: args['output'],
+        defines: args['define'],
+        packages: args['packages'],
+        enableAsserts: args['enable-asserts'],
+        enableExperiment: args.enabledExperiments.join(','),
+        soundNullSafety: args['sound-null-safety'],
+        debugFile: args['save-debugging-info'],
         verbose: verbose,
-        verbosity: argResults['verbosity'],
-        extraOptions: argResults['extra-gen-snapshot-options'],
+        verbosity: args['verbosity'],
+        extraOptions: args['extra-gen-snapshot-options'],
       );
       return 0;
     } catch (e) {
diff --git a/pkg/dartdev/lib/src/commands/create.dart b/pkg/dartdev/lib/src/commands/create.dart
index 9819614c910..8d20beec632 100644
--- a/pkg/dartdev/lib/src/commands/create.dart
+++ b/pkg/dartdev/lib/src/commands/create.dart
@@ -54,22 +54,23 @@ class CreateCommand extends DartdevCommand {
 
   @override
   FutureOr<int> run() async {
-    if (argResults['list-templates']) {
+    final args = argResults!;
+    if (args['list-templates']) {
       log.stdout(_availableTemplatesJson());
       return 0;
     }
 
-    if (argResults.rest.isEmpty) {
+    if (args.rest.isEmpty) {
       printUsage();
       return 1;
     }
 
-    String templateId = argResults['template'];
+    String templateId = args['template'];
 
-    String dir = argResults.rest.first;
+    String dir = args.rest.first;
     var targetDir = io.Directory(dir).absolute;
     dir = targetDir.path;
-    if (targetDir.existsSync() && !argResults['force']) {
+    if (targetDir.existsSync() && !args['force']) {
       log.stderr(
         "Directory '$dir' already exists "
         "(use '--force' to force project generation).",
@@ -95,13 +96,13 @@ class CreateCommand extends DartdevCommand {
     );
     log.stdout('');
 
-    var generator = getGenerator(templateId);
+    var generator = getGenerator(templateId)!;
     generator.generate(
       projectName,
       DirectoryGeneratorTarget(generator, io.Directory(dir)),
     );
 
-    if (argResults['pub']) {
+    if (args['pub']) {
       log.stdout('');
       var progress = log.progress('Running pub get');
       var process = await startDartProcess(
@@ -137,7 +138,7 @@ class CreateCommand extends DartdevCommand {
     log.stdout('');
     log.stdout(generator.getInstallInstructions(
       dir,
-      projectName,
+      scriptPath: projectName,
     ));
     log.stdout('');
 
@@ -164,7 +165,7 @@ class CreateCommand extends DartdevCommand {
       };
 
       if (generator.entrypoint != null) {
-        m['entrypoint'] = generator.entrypoint.path;
+        m['entrypoint'] = generator.entrypoint!.path;
       }
 
       return m;
diff --git a/pkg/dartdev/lib/src/commands/debug_adapter.dart b/pkg/dartdev/lib/src/commands/debug_adapter.dart
index e1a87b569d9..817f91bc961 100644
--- a/pkg/dartdev/lib/src/commands/debug_adapter.dart
+++ b/pkg/dartdev/lib/src/commands/debug_adapter.dart
@@ -53,7 +53,7 @@ class DebugAdapterCommand extends DartdevCommand {
 
   @override
   FutureOr<int> run() async {
-    final args = argResults;
+    final args = argResults!;
     final ipv6 = args[argIpv6] as bool;
 
     final server = DapServer(
diff --git a/pkg/dartdev/lib/src/commands/devtools.dart b/pkg/dartdev/lib/src/commands/devtools.dart
index e01c6bbb35e..35d216c973a 100644
--- a/pkg/dartdev/lib/src/commands/devtools.dart
+++ b/pkg/dartdev/lib/src/commands/devtools.dart
@@ -140,7 +140,7 @@ class DevToolsCommand extends DartdevCommand {
         hide: !verbose,
       );
 
-    // Deprecated and hidden argResults.
+    // Deprecated and hidden args.
     // TODO: Remove this - prefer that clients use the rest arg.
     argParser
       ..addOption(
@@ -150,7 +150,7 @@ class DevToolsCommand extends DartdevCommand {
         hide: true,
       )
 
-      // Development only argResults.
+      // Development only args.
       ..addFlag(
         argDebugMode,
         negatable: false,
@@ -159,7 +159,7 @@ class DevToolsCommand extends DartdevCommand {
       );
   }
 
-  final String customDevToolsPath;
+  final String? customDevToolsPath;
 
   @override
   String get name => 'devtools';
@@ -172,32 +172,30 @@ class DevToolsCommand extends DartdevCommand {
 
   @override
   Future<int> run() async {
-    final bool version = argResults[argVersion];
-    final bool machineMode = argResults[argMachine];
+    final args = argResults!;
+    final bool version = args[argVersion];
+    final bool machineMode = args[argMachine];
     // launchBrowser defaults based on machine-mode if not explicitly supplied.
-    final bool launchBrowser = argResults.wasParsed(argLaunchBrowser)
-        ? argResults[argLaunchBrowser]
+    final bool launchBrowser = args.wasParsed(argLaunchBrowser)
+        ? args[argLaunchBrowser]
         : !machineMode;
-    final bool enableNotifications = argResults[argEnableNotifications];
-    final bool allowEmbedding = argResults.wasParsed(argAllowEmbedding)
-        ? argResults[argAllowEmbedding]
-        : true;
+    final bool enableNotifications = args[argEnableNotifications];
+    final bool allowEmbedding =
+        args.wasParsed(argAllowEmbedding) ? args[argAllowEmbedding] : true;
 
-    final port = argResults[argPort] != null
-        ? int.tryParse(argResults[argPort]) ?? 0
-        : 0;
+    final port = args[argPort] != null ? int.tryParse(args[argPort]) ?? 0 : 0;
 
-    final bool headlessMode = argResults[argHeadlessMode];
-    final bool debugMode = argResults[argDebugMode];
+    final bool headlessMode = args[argHeadlessMode];
+    final bool debugMode = args[argDebugMode];
 
-    final numPortsToTry = argResults[argTryPorts] != null
-        ? int.tryParse(argResults[argTryPorts]) ?? 0
+    final numPortsToTry = args[argTryPorts] != null
+        ? int.tryParse(args[argTryPorts]) ?? 0
         : DevToolsServer.defaultTryPorts;
 
-    final bool verboseMode = argResults[argVerbose];
-    final String hostname = argResults[argHost];
-    final String appSizeBase = argResults[argAppSizeBase];
-    final String appSizeTest = argResults[argAppSizeTest];
+    final bool verboseMode = args[argVerbose];
+    final String? hostname = args[argHost];
+    final String? appSizeBase = args[argAppSizeBase];
+    final String? appSizeTest = args[argAppSizeTest];
 
     final sdkDir = path.dirname(sdk.dart);
     final fullSdk = sdkDir.endsWith('bin');
@@ -213,22 +211,22 @@ class DevToolsCommand extends DartdevCommand {
         },
         machineMode: machineMode,
       );
-      return null;
+      return 0;
     }
 
-    // Prefer getting the VM URI from the rest argResults; fall back on the 'vm-url'
+    // Prefer getting the VM URI from the rest args; fall back on the 'vm-url'
     // option otherwise.
-    String serviceProtocolUri;
-    if (argResults.rest.isNotEmpty) {
-      serviceProtocolUri = argResults.rest.first;
-    } else if (argResults.wasParsed(argVmUri)) {
-      serviceProtocolUri = argResults[argVmUri];
+    String? serviceProtocolUri;
+    if (args.rest.isNotEmpty) {
+      serviceProtocolUri = args.rest.first;
+    } else if (args.wasParsed(argVmUri)) {
+      serviceProtocolUri = args[argVmUri];
     }
 
     // Support collecting profile data.
-    String profileFilename;
-    if (argResults.wasParsed(argProfileMemory)) {
-      profileFilename = argResults[argProfileMemory];
+    String? profileFilename;
+    if (args.wasParsed(argProfileMemory)) {
+      profileFilename = args[argProfileMemory];
     }
     if (profileFilename != null && !path.isAbsolute(profileFilename)) {
       profileFilename = path.absolute(profileFilename);
diff --git a/pkg/dartdev/lib/src/commands/doc.dart b/pkg/dartdev/lib/src/commands/doc.dart
index 69826d43443..11e1df7c5f8 100644
--- a/pkg/dartdev/lib/src/commands/doc.dart
+++ b/pkg/dartdev/lib/src/commands/doc.dart
@@ -59,18 +59,19 @@ For additional documentation generation options, see the 'dartdoc_options.yaml'
   @override
   FutureOr<int> run() async {
     final options = <String>[];
+    final args = argResults!;
 
-    if (argResults['sdk-docs']) {
+    if (args['sdk-docs']) {
       options.add('--sdk-docs');
     } else {
       // At least one argument, the input directory, is required,
       // when we're not generating docs for the Dart SDK.
-      if (argResults.rest.isEmpty) {
+      if (args.rest.isEmpty) {
         usageException("Error: Input directory not specified");
       }
 
       // Determine input directory.
-      final dir = io.Directory(argResults.rest[0]);
+      final dir = io.Directory(args.rest[0]);
       if (!dir.existsSync()) {
         usageException("Error: Input directory doesn't exist: ${dir.path}");
       }
@@ -83,10 +84,10 @@ For additional documentation generation options, see the 'dartdoc_options.yaml'
 
     // Build remaining options.
     options.addAll([
-      '--output=${argResults['output']}',
+      '--output=${args['output']}',
       '--resources-dir=$resourcesPath',
-      if (argResults['validate-links']) '--validate-links',
-      if (argResults['dry-run']) '--no-generate-docs',
+      if (args['validate-links']) '--validate-links',
+      if (args['dry-run']) '--no-generate-docs',
       if (verbose) '--no-quiet',
     ]);
 
diff --git a/pkg/dartdev/lib/src/commands/fix.dart b/pkg/dartdev/lib/src/commands/fix.dart
index 1bdb25268d8..8fd6db97982 100644
--- a/pkg/dartdev/lib/src/commands/fix.dart
+++ b/pkg/dartdev/lib/src/commands/fix.dart
@@ -6,7 +6,7 @@ import 'dart:async';
 import 'dart:io' as io;
 
 import 'package:analysis_server_client/protocol.dart' hide AnalysisError;
-import 'package:meta/meta.dart';
+import 'package:cli_util/cli_logging.dart' show Progress;
 import 'package:path/path.dart' as path;
 
 import '../analysis_server.dart';
@@ -54,7 +54,7 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
 
   @override
   String get description {
-    if (log != null && log.ansi.useAnsi) {
+    if (log.ansi.useAnsi) {
       return cmdDescription
           .replaceAll('[', log.ansi.bold)
           .replaceAll(']', log.ansi.none);
@@ -65,15 +65,16 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
 
   @override
   FutureOr<int> run() async {
-    var dryRun = argResults['dry-run'];
-    var inTestMode = argResults['compare-to-golden'];
-    var apply = argResults['apply'];
+    final args = argResults!;
+    var dryRun = args['dry-run'];
+    var inTestMode = args['compare-to-golden'];
+    var apply = args['apply'];
     if (!apply && !dryRun && !inTestMode) {
       printUsage();
       return 0;
     }
 
-    var arguments = argResults.rest;
+    var arguments = args.rest;
     var argumentCount = arguments.length;
     if (argumentCount > 1) {
       usageException('Only one file or directory is expected.');
@@ -90,7 +91,7 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
     var modeText = dryRun ? ' (dry run)' : '';
 
     final projectName = path.basename(dirPath);
-    var computeFixesProgress = log.progress(
+    Progress? computeFixesProgress = log.progress(
         'Computing fixes in ${log.ansi.emphasized(projectName)}$modeText');
 
     var server = AnalysisServer(
@@ -131,7 +132,7 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
     await server.shutdown();
 
     if (computeFixesProgress != null) {
-      computeFixesProgress.finish(showTiming: true);
+      computeFixesProgress!.finish(showTiming: true);
       computeFixesProgress = null;
     }
 
@@ -145,7 +146,8 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
       var fileCount = detailsMap.length;
       var fixCount = detailsMap.values
           .expand((detail) => detail.fixes)
-          .fold(0, (previousValue, fixes) => previousValue + fixes.occurrences);
+          .fold<int>(0,
+              (int previousValue, fixes) => previousValue + fixes.occurrences);
 
       if (dryRun) {
         log.stdout('');
@@ -221,7 +223,7 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
         var actualIsOriginal = !fileContentCache.containsKey(filePath);
         var actualCode = actualIsOriginal
             ? originalFile.readAsStringSync()
-            : fileContentCache[filePath];
+            : fileContentCache[filePath]!;
         // Use a whitespace insensitive comparison.
         if (_compressWhitespace(actualCode) !=
             _compressWhitespace(expectedCode)) {
@@ -305,7 +307,7 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
     modifiedFilePaths
         .sort((first, second) => relative(first).compareTo(relative(second)));
     for (var filePath in modifiedFilePaths) {
-      var detail = detailsMap[filePath];
+      var detail = detailsMap[filePath]!;
       log.stdout(relative(detail.path));
       final fixes = detail.fixes.toList();
       fixes.sort((a, b) => a.code.compareTo(b.code));
@@ -320,7 +322,7 @@ To use the tool, run either ['dart fix --dry-run'] for a preview of the proposed
   /// Report that the [actualCode] produced by applying fixes to the content of
   /// [filePath] did not match the [expectedCode].
   void _reportFailure(String filePath, String actualCode, String expectedCode,
-      {@required bool actualIsOriginal}) {
+      {required bool actualIsOriginal}) {
     log.stdout('Failed when applying fixes to $filePath');
     log.stdout('Expected:');
     log.stdout(expectedCode);
diff --git a/pkg/dartdev/lib/src/commands/language_server.dart b/pkg/dartdev/lib/src/commands/language_server.dart
index 6de3df3d647..65eca061b8d 100644
--- a/pkg/dartdev/lib/src/commands/language_server.dart
+++ b/pkg/dartdev/lib/src/commands/language_server.dart
@@ -40,7 +40,7 @@ For more information about the server's capabilities and configuration, see:
   Future<int> run() async {
     final driver = server_driver.Driver();
     driver.start(
-      argResults.arguments,
+      argResults!.arguments,
       defaultToLsp: true,
     );
 
diff --git a/pkg/dartdev/lib/src/commands/migrate.dart b/pkg/dartdev/lib/src/commands/migrate.dart
index cb83e8250bd..50643263bf8 100644
--- a/pkg/dartdev/lib/src/commands/migrate.dart
+++ b/pkg/dartdev/lib/src/commands/migrate.dart
@@ -34,7 +34,7 @@ class MigrateCommand extends DartdevCommand {
   FutureOr<int> run() async {
     var cli = MigrationCli(binaryName: 'dart $name');
     try {
-      await cli.decodeCommandLineArgs(argResults, isVerbose: verbose)?.run();
+      await cli.decodeCommandLineArgs(argResults!, isVerbose: verbose)?.run();
     } on MigrationExit catch (migrationExit) {
       return migrationExit.exitCode;
     }
diff --git a/pkg/dartdev/lib/src/commands/run.dart b/pkg/dartdev/lib/src/commands/run.dart
index 2ce7fbc1cbe..ea0ce59cda6 100644
--- a/pkg/dartdev/lib/src/commands/run.dart
+++ b/pkg/dartdev/lib/src/commands/run.dart
@@ -196,22 +196,22 @@ class RunCommand extends DartdevCommand {
 
   @override
   FutureOr<int> run() async {
+    final args = argResults!;
     var mainCommand = '';
     var runArgs = <String>[];
-    if (argResults.rest.isNotEmpty) {
-      mainCommand = argResults.rest.first;
+    if (args.rest.isNotEmpty) {
+      mainCommand = args.rest.first;
       // The command line arguments after the command name.
-      runArgs = argResults.rest.skip(1).toList();
+      runArgs = args.rest.skip(1).toList();
     }
-
     if (!isProductMode) {
       // --launch-dds is provided by the VM if the VM service is to be enabled. In
       // that case, we need to launch DDS as well.
-      String launchDdsArg = argResults['launch-dds'];
+      String? launchDdsArg = args['launch-dds'];
       String ddsHost = '';
       String ddsPort = '';
 
-      bool launchDevTools = argResults['serve-devtools'];
+      bool launchDevTools = args['serve-devtools'] ?? false;
       bool launchDds = false;
       if (launchDdsArg != null) {
         launchDds = true;
@@ -219,9 +219,9 @@ class RunCommand extends DartdevCommand {
         ddsHost = ddsUrl[0];
         ddsPort = ddsUrl[1];
       }
-      final bool debugDds = argResults['debug-dds'];
+      final bool debugDds = args['debug-dds'];
 
-      bool disableServiceAuthCodes = argResults['disable-service-auth-codes'];
+      bool disableServiceAuthCodes = args['disable-service-auth-codes'];
 
       // If the user wants to start a debugging session we need to do some extra
       // work and spawn a Dart Development Service (DDS) instance. DDS is a VM
@@ -310,7 +310,7 @@ class _DebuggingSession {
     const devToolsMessagePrefix =
         'The Dart DevTools debugger and profiler is available at:';
     if (debugDds) {
-      StreamSubscription stdoutSub;
+      late StreamSubscription stdoutSub;
       stdoutSub = process.stdout.transform(utf8.decoder).listen((event) {
         if (event.startsWith(devToolsMessagePrefix)) {
           final ddsDebuggingUri = event.split(' ').last;
@@ -321,7 +321,7 @@ class _DebuggingSession {
         }
       });
     }
-    StreamSubscription stderrSub;
+    late StreamSubscription stderrSub;
     stderrSub = process.stderr.transform(utf8.decoder).listen((event) {
       final result = json.decode(event) as Map<String, dynamic>;
       final state = result['state'];
diff --git a/pkg/dartdev/lib/src/commands/test.dart b/pkg/dartdev/lib/src/commands/test.dart
index 36683af0110..31d79169c27 100644
--- a/pkg/dartdev/lib/src/commands/test.dart
+++ b/pkg/dartdev/lib/src/commands/test.dart
@@ -28,11 +28,12 @@ class TestCommand extends DartdevCommand {
 
   @override
   FutureOr<int> run() async {
+    final args = argResults!;
     try {
       final testExecutable = await getExecutableForCommand('test:test');
-      log.trace('dart $testExecutable ${argResults.rest.join(' ')}');
-      VmInteropHandler.run(testExecutable.executable, argResults.rest,
-          packageConfigOverride: testExecutable.packageConfig);
+      log.trace('dart $testExecutable ${args.rest.join(' ')}');
+      VmInteropHandler.run(testExecutable.executable, args.rest,
+          packageConfigOverride: testExecutable.packageConfig!);
       return 0;
     } on CommandResolutionFailedException catch (e) {
       if (project.hasPubspecFile) {
@@ -45,8 +46,7 @@ class TestCommand extends DartdevCommand {
         print(
             'No pubspec.yaml file found - run this command in your project folder.');
       }
-      if (argResults.rest.contains('-h') ||
-          argResults.rest.contains('--help')) {
+      if (args.rest.contains('-h') || args.rest.contains('--help')) {
         print('');
         printUsage();
       }
diff --git a/pkg/dartdev/lib/src/core.dart b/pkg/dartdev/lib/src/core.dart
index 3f4b340d55b..439bdfd8167 100644
--- a/pkg/dartdev/lib/src/core.dart
+++ b/pkg/dartdev/lib/src/core.dart
@@ -15,19 +15,19 @@ import 'experiments.dart';
 import 'sdk.dart';
 import 'utils.dart';
 
-Logger log;
+late Logger log;
 bool isDiagnostics = false;
 
 /// When set, this function is executed from the [DartdevCommand] constructor to
 /// contribute additional flags.
-void Function(ArgParser argParser, String cmdName) flagContributor;
+void Function(ArgParser argParser, String cmdName)? flagContributor;
 
 abstract class DartdevCommand extends Command<int> {
   final String _name;
   final String _description;
   final bool _verbose;
 
-  Project _project;
+  Project? _project;
 
   @override
   final bool hidden;
@@ -43,7 +43,7 @@ abstract class DartdevCommand extends Command<int> {
   @override
   String get description => _description;
 
-  ArgParser _argParser;
+  ArgParser? _argParser;
 
   @override
   ArgParser get argParser => _argParser ??= createArgParser();
@@ -70,16 +70,16 @@ abstract class DartdevCommand extends Command<int> {
 
 extension DartDevCommand on Command {
   /// Return whether commands should emit verbose output.
-  bool get verbose => globalResults['verbose'];
+  bool get verbose => globalResults!['verbose'];
 
   /// Return whether the tool should emit diagnostic output.
-  bool get diagnosticsEnabled => globalResults['diagnostics'];
+  bool get diagnosticsEnabled => globalResults!['diagnostics'];
 
   /// Return whether any Dart experiments were specified by the user.
   bool get wereExperimentsSpecified =>
       globalResults?.wasParsed(experimentFlagName) ?? false;
 
-  List<String> get specifiedExperiments => globalResults[experimentFlagName];
+  List<String> get specifiedExperiments => globalResults![experimentFlagName];
 }
 
 /// A utility method to start a Dart VM instance with the given arguments and an
@@ -89,7 +89,7 @@ extension DartDevCommand on Command {
 Future<Process> startDartProcess(
   Sdk sdk,
   List<String> arguments, {
-  String cwd,
+  String? cwd,
 }) {
   log.trace('${sdk.dart} ${arguments.join(' ')}');
   return Process.start(sdk.dart, arguments, workingDirectory: cwd);
@@ -98,7 +98,7 @@ Future<Process> startDartProcess(
 void routeToStdout(
   Process process, {
   bool logToTrace = false,
-  void Function(String str) listener,
+  void Function(String str)? listener,
 }) {
   if (isDiagnostics) {
     _streamLineTransform(process.stdout, (String line) {
@@ -136,7 +136,7 @@ void _streamLineTransform(
 class Project {
   final Directory dir;
 
-  PackageConfig _packageConfig;
+  PackageConfig? _packageConfig;
 
   Project() : dir = Directory.current;
 
@@ -147,7 +147,7 @@ class Project {
 
   bool get hasPackageConfigFile => packageConfig != null;
 
-  PackageConfig get packageConfig {
+  PackageConfig? get packageConfig {
     if (_packageConfig == null) {
       File file =
           File(path.join(dir.path, '.dart_tool', 'package_config.json'));
@@ -170,11 +170,11 @@ class PackageConfig {
 
   PackageConfig(this.contents);
 
-  List<Map<String, dynamic>> get packages {
+  List<Map<String, dynamic>?> get packages {
     List<dynamic> _packages = contents['packages'];
-    return _packages.map<Map<String, dynamic>>(castStringKeyedMap).toList();
+    return _packages.map<Map<String, dynamic>?>(castStringKeyedMap).toList();
   }
 
   bool hasDependency(String packageName) =>
-      packages.any((element) => element['name'] == packageName);
+      packages.any((element) => element!['name'] == packageName);
 }
diff --git a/pkg/dartdev/lib/src/events.dart b/pkg/dartdev/lib/src/events.dart
index 65469c01bcc..d2dad35d99f 100644
--- a/pkg/dartdev/lib/src/events.dart
+++ b/pkg/dartdev/lib/src/events.dart
@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:meta/meta.dart';
 import 'package:usage/usage.dart';
 
 /// The [String] identifier `dartdev`, used as the category in the events sent
@@ -54,17 +53,16 @@ Map<String, String> _useCdKeys(Map<_CustomDimensions, String> parameters) {
 Future<void> sendUsageEvent(
   Analytics analytics,
   String action, {
-  String label,
-  List<String> specifiedExperiments,
-  @required int exitCode,
-  @required List<String> commandFlags,
+  String? label,
+  List<String>? specifiedExperiments,
+  required int? exitCode,
+  required List<String> commandFlags,
 }) {
   /// The category stores the name of this cli tool, 'dartdev'. This matches the
   /// pattern from the flutter cli tool which always passes 'flutter' as the
   /// category.
   final category = _dartdev;
-  commandFlags =
-      commandFlags?.where((e) => e != 'enable-experiment')?.toList() ?? [];
+  commandFlags = commandFlags.where((e) => e != 'enable-experiment').toList();
   specifiedExperiments = specifiedExperiments?.toList() ?? [];
 
   // Sort the flag lists to slightly reduce the explosion of possibilities.
diff --git a/pkg/dartdev/lib/src/experiments.dart b/pkg/dartdev/lib/src/experiments.dart
index 36d4bd889a4..70acd2a79fd 100644
--- a/pkg/dartdev/lib/src/experiments.dart
+++ b/pkg/dartdev/lib/src/experiments.dart
@@ -4,6 +4,7 @@
 
 import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:args/args.dart';
+import 'package:collection/collection.dart' show IterableExtension;
 
 const experimentFlagName = 'enable-experiment';
 
@@ -53,9 +54,8 @@ extension EnabledExperimentsArg on ArgResults {
       // look for --enable-experiment=. Currently, this path is only taken for
       // the pub and test commands, as well as when we are trying to send
       // analytics.
-      final String experiments = arguments.firstWhere(
+      final String? experiments = arguments.firstWhereOrNull(
         (e) => e.startsWith('--enable-experiment='),
-        orElse: () => null,
       );
       if (experiments == null) {
         return [];
diff --git a/pkg/dartdev/lib/src/sdk.dart b/pkg/dartdev/lib/src/sdk.dart
index 2f42de6cebd..57b99c6e825 100644
--- a/pkg/dartdev/lib/src/sdk.dart
+++ b/pkg/dartdev/lib/src/sdk.dart
@@ -108,7 +108,7 @@ class Runtime {
   /// The SDK's release channel (`be`, `dev`, `beta`, `stable`).
   ///
   /// May be null if [Platform.version] does not have the expected format.
-  final String /*?*/ channel;
+  final String? channel;
 
   Runtime._(this.version, this.channel);
 
@@ -116,7 +116,7 @@ class Runtime {
     var versionString = Platform.version;
     // Exepcted format: "version (channel) ..."
     var version = versionString;
-    String /*?*/ channel;
+    String? channel;
     var versionEnd = versionString.indexOf(' ');
     if (versionEnd > 0) {
       version = versionString.substring(0, versionEnd);
diff --git a/pkg/dartdev/lib/src/templates.dart b/pkg/dartdev/lib/src/templates.dart
index 3d36844cbb2..ee1938a5b91 100644
--- a/pkg/dartdev/lib/src/templates.dart
+++ b/pkg/dartdev/lib/src/templates.dart
@@ -4,6 +4,7 @@
 
 import 'dart:convert' show utf8;
 
+import 'package:collection/collection.dart' show IterableExtension;
 import 'package:meta/meta.dart';
 import 'package:path/path.dart' as p;
 
@@ -24,8 +25,8 @@ final List<Generator> generators = [
   WebSimpleGenerator(),
 ];
 
-Generator getGenerator(String id) =>
-    generators.firstWhere((g) => g.id == id, orElse: () => null);
+Generator? getGenerator(String id) =>
+    generators.firstWhereOrNull((g) => g.id == id);
 
 /// An abstract class which both defines a template generator and can generate a
 /// user project based on this template.
@@ -36,12 +37,12 @@ abstract class Generator implements Comparable<Generator> {
   final List<String> categories;
 
   final List<TemplateFile> files = [];
-  TemplateFile _entrypoint;
+  TemplateFile? _entrypoint;
 
   /// Lazily initialized cache for lower-case if [id].
   ///
   /// Used by [compareTo].
-  String /*?*/ _lowerCaseId;
+  String? _lowerCaseId;
 
   Generator(
     this.id,
@@ -54,7 +55,7 @@ abstract class Generator implements Comparable<Generator> {
 
   /// The entrypoint of the application; the main file for the project, which an
   /// IDE might open after creating the project.
-  TemplateFile get entrypoint => _entrypoint;
+  TemplateFile? get entrypoint => _entrypoint;
 
   TemplateFile addFile(String path, String contents) {
     return addTemplateFile(TemplateFile(path, contents));
@@ -67,22 +68,21 @@ abstract class Generator implements Comparable<Generator> {
   }
 
   /// Return the template file wih the given [path].
-  TemplateFile getFile(String path) =>
-      files.firstWhere((file) => file.path == path, orElse: () => null);
+  TemplateFile? getFile(String path) =>
+      files.firstWhereOrNull((file) => file.path == path);
 
   /// Set the main entrypoint of this template. This is the 'most important'
   /// file of this template. An IDE might use this information to open this file
   /// after the user's project is generated.
   void setEntrypoint(TemplateFile entrypoint) {
     if (_entrypoint != null) throw StateError('entrypoint already set');
-    if (entrypoint == null) throw StateError('entrypoint is null');
     _entrypoint = entrypoint;
   }
 
   void generate(
     String projectName,
     GeneratorTarget target, {
-    Map<String, String> additionalVars,
+    Map<String, String>? additionalVars,
   }) {
     final vars = {
       'projectName': projectName,
@@ -111,9 +111,9 @@ abstract class Generator implements Comparable<Generator> {
   /// (e.g., bin/foo.dart) **without** an extension. If null, the implicit run
   /// command will be output by default (e.g., dart run).
   String getInstallInstructions(
-    String directory,
-    String scriptPath,
-  ) {
+    String directory, {
+    String? scriptPath,
+  }) {
     final buffer = StringBuffer();
     buffer.writeln('  cd ${p.relative(directory)}');
     if (scriptPath != null) {
@@ -208,5 +208,5 @@ String substituteVars(String str, Map<String, String> vars) {
   }
 
   return str.replaceAllMapped(
-      _substituteRegExp, (match) => vars[match[1]] ?? match[0]);
+      _substituteRegExp, (match) => vars[match[1]!] ?? match[0]!);
 }
diff --git a/pkg/dartdev/lib/src/templates/console_full.dart b/pkg/dartdev/lib/src/templates/console_full.dart
index 553ceeb0120..d4c2965c430 100644
--- a/pkg/dartdev/lib/src/templates/console_full.dart
+++ b/pkg/dartdev/lib/src/templates/console_full.dart
@@ -25,10 +25,10 @@ class ConsoleFullGenerator extends DefaultGenerator {
 
   @override
   String getInstallInstructions(
-    String directory,
-    String scriptPath,
-  ) =>
-      super.getInstallInstructions(directory, null);
+    String directory, {
+    String? scriptPath,
+  }) =>
+      super.getInstallInstructions(directory);
 }
 
 final String _pubspec = '''
diff --git a/pkg/dartdev/lib/src/templates/console_simple.dart b/pkg/dartdev/lib/src/templates/console_simple.dart
index 5c6d381a83e..ed6f79373ed 100644
--- a/pkg/dartdev/lib/src/templates/console_simple.dart
+++ b/pkg/dartdev/lib/src/templates/console_simple.dart
@@ -17,16 +17,16 @@ class ConsoleSimpleGenerator extends DefaultGenerator {
     addFile('pubspec.yaml', _pubspec);
     addFile('README.md', _readme);
     setEntrypoint(
-      addFile('bin/__projectName__.dart', main),
+      addFile('bin/__projectName__.dart', mainSrc),
     );
   }
 
   @override
   String getInstallInstructions(
-    String directory,
-    String scriptPath,
-  ) =>
-      super.getInstallInstructions(directory, null);
+    String directory, {
+    String? scriptPath,
+  }) =>
+      super.getInstallInstructions(directory);
 }
 
 final String _pubspec = '''
@@ -49,7 +49,7 @@ final String _readme = '''
 A simple command-line application.
 ''';
 
-final String main = '''
+final String mainSrc = '''
 void main(List<String> arguments) {
   print('Hello world!');
 }
diff --git a/pkg/dartdev/lib/src/templates/package_simple.dart b/pkg/dartdev/lib/src/templates/package_simple.dart
index 591f110eb1e..9827dd7aeee 100644
--- a/pkg/dartdev/lib/src/templates/package_simple.dart
+++ b/pkg/dartdev/lib/src/templates/package_simple.dart
@@ -26,12 +26,12 @@ class PackageSimpleGenerator extends DefaultGenerator {
 
   @override
   String getInstallInstructions(
-    String directory,
-    String scriptPath,
-  ) =>
+    String directory, {
+    String? scriptPath,
+  }) =>
       super.getInstallInstructions(
         directory,
-        'example/${scriptPath}_example',
+        scriptPath: 'example/${scriptPath}_example',
       );
 }
 
diff --git a/pkg/dartdev/lib/src/templates/server_shelf.dart b/pkg/dartdev/lib/src/templates/server_shelf.dart
index ed6b73017ef..c075f022df4 100644
--- a/pkg/dartdev/lib/src/templates/server_shelf.dart
+++ b/pkg/dartdev/lib/src/templates/server_shelf.dart
@@ -26,12 +26,12 @@ class ServerShelfGenerator extends DefaultGenerator {
 
   @override
   String getInstallInstructions(
-    String directory,
-    String scriptPath,
-  ) =>
+    String directory, {
+    String? scriptPath,
+  }) =>
       super.getInstallInstructions(
         directory,
-        'bin/server',
+        scriptPath: 'bin/server',
       );
 }
 
diff --git a/pkg/dartdev/lib/src/templates/web_simple.dart b/pkg/dartdev/lib/src/templates/web_simple.dart
index 6ea2eb18a6b..e22be742bd4 100644
--- a/pkg/dartdev/lib/src/templates/web_simple.dart
+++ b/pkg/dartdev/lib/src/templates/web_simple.dart
@@ -27,9 +27,9 @@ class WebSimpleGenerator extends DefaultGenerator {
 
   @override
   String getInstallInstructions(
-    String directory,
-    String scriptPath,
-  ) =>
+    String directory, {
+    String? scriptPath,
+  }) =>
       '  cd ${p.relative(directory)}\n'
       '  dart pub global activate webdev\n'
       '  webdev serve';
diff --git a/pkg/dartdev/lib/src/utils.dart b/pkg/dartdev/lib/src/utils.dart
index c36d6fa9b72..f4c5676b958 100644
--- a/pkg/dartdev/lib/src/utils.dart
+++ b/pkg/dartdev/lib/src/utils.dart
@@ -8,14 +8,14 @@ import 'package:path/path.dart' as p;
 
 /// For commands where we are able to initialize the [ArgParser], this value
 /// is used as the usageLineLength.
-int get dartdevUsageLineLength =>
+int? get dartdevUsageLineLength =>
     stdout.hasTerminal ? stdout.terminalColumns : null;
 
 /// Given a data structure which is a Map of String to dynamic values, return
 /// the same structure (`Map<String, dynamic>`) with the correct runtime types.
 Map<String, dynamic> castStringKeyedMap(dynamic untyped) {
-  final Map<dynamic, dynamic> map = untyped as Map<dynamic, dynamic>;
-  return map?.cast<String, dynamic>();
+  final Map<dynamic, dynamic> map = untyped! as Map<dynamic, dynamic>;
+  return map.cast<String, dynamic>();
 }
 
 /// Emit the given word with the correct pluralization.
@@ -31,7 +31,7 @@ String relativePath(String filePath, Directory dir) {
 }
 
 /// String utility to trim some suffix from the end of a [String].
-String trimEnd(String s, String suffix) {
+String? trimEnd(String? s, String? suffix) {
   if (s != null && suffix != null && suffix.isNotEmpty && s.endsWith(suffix)) {
     return s.substring(0, s.length - suffix.length);
   }
@@ -45,7 +45,7 @@ extension FileSystemEntityExtension on FileSystemEntity {
 }
 
 /// Wraps [text] to the given [width], if provided.
-String wrapText(String text, {int width}) {
+String wrapText(String text, {int? width}) {
   if (width == null) {
     return text;
   }
diff --git a/pkg/dartdev/lib/src/vm_interop_handler.dart b/pkg/dartdev/lib/src/vm_interop_handler.dart
index 6ff7bfa24ad..0913a93638e 100644
--- a/pkg/dartdev/lib/src/vm_interop_handler.dart
+++ b/pkg/dartdev/lib/src/vm_interop_handler.dart
@@ -4,13 +4,11 @@
 
 import 'dart:isolate';
 
-import 'package:meta/meta.dart';
-
 /// Contains methods used to communicate DartDev results back to the VM.
 abstract class VmInteropHandler {
   /// Initializes [VmInteropHandler] to utilize [port] to communicate with the
   /// VM.
-  static void initialize(SendPort port) => _port = port;
+  static void initialize(SendPort? port) => _port = port;
 
   /// Notifies the VM to run [script] with [args] upon DartDev exit.
   ///
@@ -18,10 +16,10 @@ abstract class VmInteropHandler {
   static void run(
     String script,
     List<String> args, {
-    @required String packageConfigOverride,
+    String? packageConfigOverride,
   }) {
-    assert(_port != null);
-    if (_port == null) return;
+    final port = _port;
+    if (port == null) return;
     final message = <dynamic>[
       _kResultRun,
       script,
@@ -29,21 +27,21 @@ abstract class VmInteropHandler {
       // Copy the list so it doesn't get GC'd underneath us.
       args.toList()
     ];
-    _port.send(message);
+    port.send(message);
   }
 
   /// Notifies the VM that DartDev has completed running. If provided a
   /// non-zero [exitCode], the VM will terminate with the given exit code.
-  static void exit(int exitCode) {
-    assert(_port != null);
-    if (_port == null) return;
+  static void exit(int? exitCode) {
+    final port = _port;
+    if (port == null) return;
     final message = <dynamic>[_kResultExit, exitCode];
-    _port.send(message);
+    port.send(message);
   }
 
   // Note: keep in sync with runtime/bin/dartdev_isolate.h
   static const int _kResultRun = 1;
   static const int _kResultExit = 2;
 
-  static SendPort _port;
+  static SendPort? _port;
 }
diff --git a/pkg/dartdev/pubspec.yaml b/pkg/dartdev/pubspec.yaml
index ea173173bc5..51e57b2aca6 100644
--- a/pkg/dartdev/pubspec.yaml
+++ b/pkg/dartdev/pubspec.yaml
@@ -4,7 +4,7 @@ name: dartdev
 publish_to: none
 
 environment:
-  sdk: '>=2.6.0 <3.0.0'
+  sdk: '>=2.12.0 <3.0.0'
 dependencies:
   analysis_server:
     path: ../analysis_server
@@ -14,6 +14,7 @@ dependencies:
     path: ../analyzer
   args: any
   cli_util: any
+  collection: any
   dart2native:
     path: ../dart2native
   dart_style: any
diff --git a/pkg/dartdev/test/analysis_server_test.dart b/pkg/dartdev/test/analysis_server_test.dart
index 975eb86b39a..bd24aed275a 100644
--- a/pkg/dartdev/test/analysis_server_test.dart
+++ b/pkg/dartdev/test/analysis_server_test.dart
@@ -14,14 +14,14 @@ import 'utils.dart';
 
 void main() {
   group('AnalysisServer', () {
-    TestProject p;
+    late TestProject p;
 
     setUp(() {
       log = Logger.standard();
       p = project();
     });
 
-    tearDown(() async => await p?.dispose());
+    tearDown(() async => await p.dispose());
 
     test('can start', () async {
       AnalysisServer server = AnalysisServer(
diff --git a/pkg/dartdev/test/commands/analyze_test.dart b/pkg/dartdev/test/commands/analyze_test.dart
index 60bbb1a67fd..04fc049134a 100644
--- a/pkg/dartdev/test/commands/analyze_test.dart
+++ b/pkg/dartdev/test/commands/analyze_test.dart
@@ -172,7 +172,7 @@ void defineAnalysisError() {
 }
 
 void defineAnalyze() {
-  TestProject p;
+  TestProject? p;
 
   setUp(() => p = null);
 
@@ -180,7 +180,7 @@ void defineAnalyze() {
 
   test('--help', () async {
     p = project();
-    var result = await p.run(['analyze', '--help']);
+    var result = await p!.run(['analyze', '--help']);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -190,7 +190,7 @@ void defineAnalyze() {
 
   test('--help --verbose', () async {
     p = project();
-    var result = await p.run(['analyze', '--help', '--verbose']);
+    var result = await p!.run(['analyze', '--help', '--verbose']);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -199,14 +199,15 @@ void defineAnalyze() {
   });
 
   group('multiple items', () {
-    TestProject secondProject;
+    late TestProject secondProject;
 
-    tearDown(() async => await secondProject?.dispose());
+    tearDown(() async => await secondProject.dispose());
 
     test('folder and file', () async {
       p = project(mainSrc: "int get foo => 'str';\n");
       secondProject = project(mainSrc: "int get foo => 'str';\n");
-      var result = await p.run(['analyze', p.dirPath, secondProject.mainPath]);
+      var result =
+          await p!.run(['analyze', p!.dirPath, secondProject.mainPath]);
 
       expect(result.exitCode, 3);
       expect(result.stderr, isEmpty);
@@ -219,7 +220,7 @@ void defineAnalyze() {
     test('two folders', () async {
       p = project(mainSrc: "int get foo => 'str';\n");
       secondProject = project(mainSrc: "int get foo => 'str';\n");
-      var result = await p.run(['analyze', p.dirPath, secondProject.dirPath]);
+      var result = await p!.run(['analyze', p!.dirPath, secondProject.dirPath]);
 
       expect(result.exitCode, 3);
       expect(result.stderr, isEmpty);
@@ -232,7 +233,7 @@ void defineAnalyze() {
 
   test('no such directory', () async {
     p = project();
-    var result = await p.run(['analyze', '/no/such/dir1/']);
+    var result = await p!.run(['analyze', '/no/such/dir1/']);
 
     expect(result.exitCode, 64);
     expect(result.stdout, isEmpty);
@@ -244,7 +245,7 @@ void defineAnalyze() {
   test('current working directory', () async {
     p = project(mainSrc: 'int get foo => 1;\n');
 
-    var result = await p.run(['analyze'], workingDir: p.dirPath);
+    var result = await p!.run(['analyze'], workingDir: p!.dirPath);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -254,7 +255,7 @@ void defineAnalyze() {
   group('single directory', () {
     test('no errors', () async {
       p = project(mainSrc: 'int get foo => 1;\n');
-      var result = await p.run(['analyze', p.dirPath]);
+      var result = await p!.run(['analyze', p!.dirPath]);
 
       expect(result.exitCode, 0);
       expect(result.stderr, isEmpty);
@@ -263,7 +264,7 @@ void defineAnalyze() {
 
     test('one error', () async {
       p = project(mainSrc: "int get foo => 'str';\n");
-      var result = await p.run(['analyze', p.dirPath]);
+      var result = await p!.run(['analyze', p!.dirPath]);
 
       expect(result.exitCode, 3);
       expect(result.stderr, isEmpty);
@@ -275,7 +276,7 @@ void defineAnalyze() {
 
     test('two errors', () async {
       p = project(mainSrc: "int get foo => 'str';\nint get bar => 'str';\n");
-      var result = await p.run(['analyze', p.dirPath]);
+      var result = await p!.run(['analyze', p!.dirPath]);
 
       expect(result.exitCode, 3);
       expect(result.stderr, isEmpty);
@@ -286,7 +287,7 @@ void defineAnalyze() {
   group('single file', () {
     test('no errors', () async {
       p = project(mainSrc: 'int get foo => 1;\n');
-      var result = await p.run(['analyze', p.mainPath]);
+      var result = await p!.run(['analyze', p!.mainPath]);
 
       expect(result.exitCode, 0);
       expect(result.stderr, isEmpty);
@@ -295,7 +296,7 @@ void defineAnalyze() {
 
     test('one error', () async {
       p = project(mainSrc: "int get foo => 'str';\n");
-      var result = await p.run(['analyze', p.mainPath]);
+      var result = await p!.run(['analyze', p!.mainPath]);
 
       expect(result.exitCode, 3);
       expect(result.stderr, isEmpty);
@@ -310,7 +311,7 @@ void defineAnalyze() {
     p = project(
         mainSrc: _unusedImportCodeSnippet,
         analysisOptions: _unusedImportAnalysisOptions);
-    var result = await p.run(['analyze', '--fatal-warnings', p.dirPath]);
+    var result = await p!.run(['analyze', '--fatal-warnings', p!.dirPath]);
 
     expect(result.exitCode, equals(2));
     expect(result.stderr, isEmpty);
@@ -321,7 +322,7 @@ void defineAnalyze() {
     p = project(
         mainSrc: _unusedImportCodeSnippet,
         analysisOptions: _unusedImportAnalysisOptions);
-    var result = await p.run(['analyze', p.dirPath]);
+    var result = await p!.run(['analyze', p!.dirPath]);
 
     expect(result.exitCode, equals(2));
     expect(result.stderr, isEmpty);
@@ -332,7 +333,7 @@ void defineAnalyze() {
     p = project(
         mainSrc: _unusedImportCodeSnippet,
         analysisOptions: _unusedImportAnalysisOptions);
-    var result = await p.run(['analyze', '--no-fatal-warnings', p.dirPath]);
+    var result = await p!.run(['analyze', '--no-fatal-warnings', p!.dirPath]);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -341,7 +342,7 @@ void defineAnalyze() {
 
   test('info implicit no --fatal-infos', () async {
     p = project(mainSrc: dartVersionFilePrefix2_9 + 'String foo() {}');
-    var result = await p.run(['analyze', p.dirPath]);
+    var result = await p!.run(['analyze', p!.dirPath]);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -350,7 +351,7 @@ void defineAnalyze() {
 
   test('info --fatal-infos', () async {
     p = project(mainSrc: dartVersionFilePrefix2_9 + 'String foo() {}');
-    var result = await p.run(['analyze', '--fatal-infos', p.dirPath]);
+    var result = await p!.run(['analyze', '--fatal-infos', p!.dirPath]);
 
     expect(result.exitCode, 1);
     expect(result.stderr, isEmpty);
@@ -364,7 +365,7 @@ int f() {
   var one = 1;
   return result;
 }''');
-    var result = await p.run(['analyze', '--verbose', p.dirPath]);
+    var result = await p!.run(['analyze', '--verbose', p!.dirPath]);
 
     expect(result.exitCode, 3);
     expect(result.stderr, isEmpty);
@@ -386,7 +387,7 @@ import 'package:foo/foo.dart';
 void f() {
   my_foo;
 }''');
-      p.file('my_packages.json', '''
+      p!.file('my_packages.json', '''
 {
   "configVersion": 2,
   "packages": [
@@ -399,10 +400,10 @@ void f() {
   ]
 }
 ''');
-      var result = await p.run([
+      var result = await p!.run([
         'analyze',
-        '--packages=${p.findFile('my_packages.json').path}',
-        p.dirPath,
+        '--packages=${p!.findFile('my_packages.json')!.path}',
+        p!.dirPath,
       ]);
 
       expect(result.exitCode, 0);
@@ -412,10 +413,10 @@ void f() {
 
     test('not existing', () async {
       p = project();
-      var result = await p.run([
+      var result = await p!.run([
         'analyze',
         '--packages=no.such.file',
-        p.dirPath,
+        p!.dirPath,
       ]);
 
       expect(result.exitCode, 64);
@@ -428,10 +429,10 @@ void f() {
     var cache = project(name: 'cache');
 
     p = project(mainSrc: 'var v = 0;');
-    var result = await p.run([
+    var result = await p!.run([
       'analyze',
       '--cache=${cache.dirPath}',
-      p.mainPath,
+      p!.mainPath,
     ]);
 
     expect(result.exitCode, 0);
diff --git a/pkg/dartdev/test/commands/compile_test.dart b/pkg/dartdev/test/commands/compile_test.dart
index 2facc8c1bf6..82478e9bab8 100644
--- a/pkg/dartdev/test/commands/compile_test.dart
+++ b/pkg/dartdev/test/commands/compile_test.dart
@@ -468,7 +468,7 @@ void main() {}
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
     expect(File(outFile).existsSync(), true,
@@ -497,7 +497,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
   }, skip: isRunningOnIA32);
@@ -566,7 +566,7 @@ void main() {}
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
     expect(File(outFile).existsSync(), true,
@@ -595,7 +595,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
   });
@@ -664,7 +664,7 @@ void main() {}
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
     expect(File(outFile).existsSync(), true,
@@ -693,7 +693,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
   }, skip: isRunningOnIA32);
@@ -720,7 +720,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stdout, contains('Warning: '));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
@@ -747,7 +747,8 @@ void main() {
     expect(
       result.stderr,
       predicate(
-        (o) => '$o'.contains('Unexpected arguments after Dart entry point.'),
+        (dynamic o) =>
+            '$o'.contains('Unexpected arguments after Dart entry point.'),
       ),
     );
     expect(result.exitCode, 64);
@@ -818,7 +819,7 @@ void main() {}
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
     expect(File(outFile).existsSync(), true,
@@ -846,7 +847,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, contains('must be assigned before it can be used'));
     expect(result.exitCode, 254);
   });
@@ -872,7 +873,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, contains('Warning:'));
     expect(result.exitCode, 0);
   });
@@ -941,7 +942,7 @@ void main() {}
       ],
     );
 
-    expect(result.stdout, predicate((o) => '$o'.contains('[foo]')));
+    expect(result.stdout, predicate((dynamic o) => '$o'.contains('[foo]')));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
     expect(File(outFile).existsSync(), true,
@@ -965,7 +966,7 @@ void main() {}
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
     expect(File(outFile).existsSync(), true,
@@ -993,7 +994,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, contains('must be assigned before it can be used'));
     expect(result.exitCode, 254);
   });
@@ -1019,7 +1020,7 @@ void main() {
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, contains('Warning:'));
     expect(result.exitCode, 0);
   });
diff --git a/pkg/dartdev/test/commands/create_integration_test.dart b/pkg/dartdev/test/commands/create_integration_test.dart
index 4856b4750e4..e73a16d98bf 100644
--- a/pkg/dartdev/test/commands/create_integration_test.dart
+++ b/pkg/dartdev/test/commands/create_integration_test.dart
@@ -14,7 +14,7 @@ void main() {
 }
 
 void defineCreateTests() {
-  TestProject p;
+  TestProject? p;
 
   setUp(() => p = null);
 
@@ -25,7 +25,7 @@ void defineCreateTests() {
     test(templateId, () async {
       p = project();
 
-      ProcessResult createResult = await p.run([
+      ProcessResult createResult = await p!.run([
         'create',
         '--force',
         '--template',
@@ -37,11 +37,11 @@ void defineCreateTests() {
       // Validate that the project analyzes cleanly.
       // TODO: Should we use --fatal-infos here?
       ProcessResult analyzeResult =
-          await p.run(['analyze'], workingDir: p.dir.path);
+          await p!.run(['analyze'], workingDir: p!.dir.path);
       expect(analyzeResult.exitCode, 0, reason: analyzeResult.stdout);
 
       // Validate that the code is well formatted.
-      ProcessResult formatResult = await p.run([
+      ProcessResult formatResult = await p!.run([
         'format',
         '--output',
         'none',
diff --git a/pkg/dartdev/test/commands/create_test.dart b/pkg/dartdev/test/commands/create_test.dart
index 899c7b0cf44..872309efc1d 100644
--- a/pkg/dartdev/test/commands/create_test.dart
+++ b/pkg/dartdev/test/commands/create_test.dart
@@ -17,7 +17,7 @@ void main() {
 }
 
 void defineCreateTests() {
-  TestProject p;
+  TestProject? p;
 
   setUp(() => p = null);
 
@@ -25,7 +25,7 @@ void defineCreateTests() {
 
   test('--help', () async {
     p = project();
-    var result = await p.run(['create', '--help']);
+    var result = await p!.run(['create', '--help']);
 
     expect(result.stdout, contains('Create a new Dart project.'));
     expect(
@@ -40,7 +40,7 @@ void defineCreateTests() {
 
   test('--help --verbose', () async {
     p = project();
-    var result = await p.run(['create', '--help', '--verbose']);
+    var result = await p!.run(['create', '--help', '--verbose']);
 
     expect(result.stdout, contains('Create a new Dart project.'));
     expect(
@@ -67,7 +67,7 @@ void defineCreateTests() {
   test('list templates', () async {
     p = project();
 
-    ProcessResult result = await p.run(['create', '--list-templates']);
+    ProcessResult result = await p!.run(['create', '--list-templates']);
     expect(result.exitCode, 0);
 
     String output = result.stdout.toString();
@@ -81,7 +81,7 @@ void defineCreateTests() {
   test('no directory given', () async {
     p = project();
 
-    ProcessResult result = await p.run([
+    ProcessResult result = await p!.run([
       'create',
     ]);
     expect(result.exitCode, 1);
@@ -90,15 +90,15 @@ void defineCreateTests() {
   test('directory already exists', () async {
     p = project();
 
-    ProcessResult result = await p.run(
-        ['create', '--template', CreateCommand.defaultTemplateId, p.dir.path]);
+    ProcessResult result = await p!.run(
+        ['create', '--template', CreateCommand.defaultTemplateId, p!.dir.path]);
     expect(result.exitCode, 73);
   });
 
   test('project in current directory', () async {
     p = project();
     final projectDir = Directory('foo')..createSync();
-    final result = await p.run(
+    final result = await p!.run(
       ['create', '--force', '.'],
       workingDir: projectDir.path,
     );
@@ -109,7 +109,7 @@ void defineCreateTests() {
 
   test('project with normalized package name', () async {
     p = project();
-    final result = await p.run(['create', 'requires-normalization']);
+    final result = await p!.run(['create', 'requires-normalization']);
     expect(result.stderr, isEmpty);
     expect(
         result.stdout,
@@ -120,7 +120,7 @@ void defineCreateTests() {
 
   test('project with an invalid package name', () async {
     p = project();
-    final result = await p.run(['create', 'bad-package^name']);
+    final result = await p!.run(['create', 'bad-package^name']);
     expect(
       result.stderr,
       contains(
@@ -134,8 +134,8 @@ void defineCreateTests() {
   test('bad template id', () async {
     p = project();
 
-    ProcessResult result = await p
-        .run(['create', '--no-pub', '--template', 'foo-bar', p.dir.path]);
+    ProcessResult result = await p!
+        .run(['create', '--no-pub', '--template', 'foo-bar', p!.dir.path]);
     expect(result.exitCode, isNot(0));
   });
 
@@ -144,7 +144,7 @@ void defineCreateTests() {
     test(templateId, () async {
       p = project();
       const projectName = 'template_project';
-      ProcessResult result = await p.run([
+      ProcessResult result = await p!.run([
         'create',
         '--force',
         '--no-pub',
@@ -154,9 +154,9 @@ void defineCreateTests() {
       ]);
       expect(result.exitCode, 0);
 
-      String entry = templates.getGenerator(templateId).entrypoint.path;
+      String entry = templates.getGenerator(templateId)!.entrypoint!.path;
       entry = entry.replaceAll('__projectName__', projectName);
-      File entryFile = File(path.join(p.dir.path, projectName, entry));
+      File entryFile = File(path.join(p!.dir.path, projectName, entry));
 
       expect(entryFile.existsSync(), true,
           reason: 'File not found: ${entryFile.path}');
@@ -168,7 +168,7 @@ void defineCreateTests() {
       const dir = 'foo';
       const projectName = dir;
       final lines = generator
-          .getInstallInstructions(dir, projectName)
+          .getInstallInstructions(dir, scriptPath: projectName)
           .split('\n')
           .map((e) => e.trim())
           .toList();
diff --git a/pkg/dartdev/test/commands/devtools_test.dart b/pkg/dartdev/test/commands/devtools_test.dart
index 24cb80b4208..08f1cd033db 100644
--- a/pkg/dartdev/test/commands/devtools_test.dart
+++ b/pkg/dartdev/test/commands/devtools_test.dart
@@ -14,9 +14,9 @@ void main() {
 }
 
 void devtools() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('--help', () async {
     p = project();
@@ -47,7 +47,7 @@ void devtools() {
   });
 
   group('integration', () {
-    Process process;
+    Process? process;
 
     tearDown(() {
       process?.kill();
@@ -58,8 +58,8 @@ void devtools() {
 
       // start the devtools server
       process = await p.start(['devtools', '--no-launch-browser', '--machine']);
-
-      final Stream<String> inStream = process.stdout
+      process!.stderr.transform(utf8.decoder).listen(print);
+      final Stream<String> inStream = process!.stdout
           .transform<String>(utf8.decoder)
           .transform<String>(const LineSplitter());
 
@@ -89,7 +89,7 @@ void devtools() {
       expect(contents, contains('DevTools'));
 
       // kill the process
-      process.kill();
+      process!.kill();
       process = null;
     });
   });
diff --git a/pkg/dartdev/test/commands/fix_test.dart b/pkg/dartdev/test/commands/fix_test.dart
index c6382f43f66..2d21669806a 100644
--- a/pkg/dartdev/test/commands/fix_test.dart
+++ b/pkg/dartdev/test/commands/fix_test.dart
@@ -18,9 +18,9 @@ void main() {
 const runFromSource = false;
 
 void defineFix() {
-  TestProject p;
+  TestProject? p;
 
-  ProcessResult result;
+  late ProcessResult result;
 
   final bullet = Logger.standard().ansi.bullet;
 
@@ -52,18 +52,18 @@ ${result.stderr}
 ''');
   }
 
-  Future<ProcessResult> runFix(List<String> args, {String workingDir}) async {
+  Future<ProcessResult> runFix(List<String> args, {String? workingDir}) async {
     if (runFromSource) {
       var binary = path.join(Directory.current.path, 'bin', 'dartdev.dart');
-      return await p.run([binary, 'fix', ...?args], workingDir: workingDir);
+      return await p!.run([binary, 'fix', ...args], workingDir: workingDir);
     }
-    return await p.run(['fix', ...args], workingDir: workingDir);
+    return await p!.run(['fix', ...args], workingDir: workingDir);
   }
 
   test('--help', () async {
     p = project(mainSrc: 'int get foo => 1;\n');
 
-    var result = await runFix([p.dirPath, '--help']);
+    var result = await runFix([p!.dirPath, '--help']);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -79,7 +79,7 @@ ${result.stderr}
   test('--help --verbose', () async {
     p = project(mainSrc: 'int get foo => 1;\n');
 
-    var result = await runFix([p.dirPath, '--help', '--verbose']);
+    var result = await runFix([p!.dirPath, '--help', '--verbose']);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -98,7 +98,7 @@ ${result.stderr}
   test('none', () async {
     p = project(mainSrc: 'int get foo => 1;\n');
 
-    var result = await runFix([p.dirPath]);
+    var result = await runFix([p!.dirPath]);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -109,7 +109,7 @@ ${result.stderr}
   test('--apply (none)', () async {
     p = project(mainSrc: 'int get foo => 1;\n');
 
-    var result = await runFix(['--apply', p.dirPath]);
+    var result = await runFix(['--apply', p!.dirPath]);
 
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
@@ -128,7 +128,7 @@ linter:
 ''',
     );
 
-    var result = await runFix(['--apply'], workingDir: p.dirPath);
+    var result = await runFix(['--apply'], workingDir: p!.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
     expect(
@@ -158,7 +158,7 @@ linter:
     - prefer_single_quotes
 ''',
     );
-    var result = await runFix(['--dry-run', '.'], workingDir: p.dirPath);
+    var result = await runFix(['--dry-run', '.'], workingDir: p!.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
     expect(
@@ -182,7 +182,7 @@ linter:
     - prefer_single_quotes
 ''',
     );
-    var result = await runFix(['--apply', '.'], workingDir: p.dirPath);
+    var result = await runFix(['--apply', '.'], workingDir: p!.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
     expect(
@@ -207,7 +207,7 @@ linter:
     - prefer_single_quotes
 ''',
     );
-    var result = await runFix(['--apply', '.'], workingDir: p.dirPath);
+    var result = await runFix(['--apply', '.'], workingDir: p!.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
     expect(
@@ -235,7 +235,7 @@ linter:
     - prefer_single_quotes
 ''',
     );
-    var result = await runFix(['--apply', '.'], workingDir: p.dirPath);
+    var result = await runFix(['--apply', '.'], workingDir: p!.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
     expect(result.stdout, contains('Nothing to fix!'));
@@ -253,7 +253,7 @@ linter:
     - prefer_single_quotes
 ''',
     );
-    var result = await runFix(['--apply', '.'], workingDir: p.dirPath);
+    var result = await runFix(['--apply', '.'], workingDir: p!.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
     expect(result.stdout, contains('Nothing to fix!'));
@@ -272,7 +272,7 @@ linter:
     - prefer_single_quotes
 ''',
     );
-    var result = await runFix(['--apply', '.'], workingDir: p.dirPath);
+    var result = await runFix(['--apply', '.'], workingDir: p!.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
     expect(
@@ -305,7 +305,7 @@ linter:
     - prefer_single_quotes
 ''',
       );
-      p.file('lib/main.dart.expect', '''
+      p!.file('lib/main.dart.expect', '''
 class A {
   String a() => '';
 }
@@ -315,7 +315,7 @@ class B extends A {
 }
 ''');
       result =
-          await runFix(['--compare-to-golden', '.'], workingDir: p.dirPath);
+          await runFix(['--compare-to-golden', '.'], workingDir: p!.dirPath);
       assertResult(exitCode: 1);
     });
 
@@ -337,7 +337,7 @@ linter:
     - prefer_single_quotes
 ''',
       );
-      p.file('lib/main.dart.expect', '''
+      p!.file('lib/main.dart.expect', '''
 class A {
   String a() => '';
 }
@@ -348,7 +348,7 @@ class B extends A {
 }
 ''');
       result =
-          await runFix(['--compare-to-golden', '.'], workingDir: p.dirPath);
+          await runFix(['--compare-to-golden', '.'], workingDir: p!.dirPath);
       assertResult();
     });
 
@@ -371,7 +371,7 @@ linter:
 ''',
       );
       result =
-          await runFix(['--compare-to-golden', '.'], workingDir: p.dirPath);
+          await runFix(['--compare-to-golden', '.'], workingDir: p!.dirPath);
       assertResult(exitCode: 1);
     });
 
@@ -379,14 +379,14 @@ linter:
       p = project(mainSrc: '''
 class C {}
 ''');
-      p.file('lib/main.dart.expect', '''
+      p!.file('lib/main.dart.expect', '''
 class C {}
 ''');
-      p.file('lib/secondary.dart.expect', '''
+      p!.file('lib/secondary.dart.expect', '''
 class A {}
 ''');
       result =
-          await runFix(['--compare-to-golden', '.'], workingDir: p.dirPath);
+          await runFix(['--compare-to-golden', '.'], workingDir: p!.dirPath);
       assertResult(exitCode: 1);
     });
 
@@ -403,13 +403,13 @@ linter:
     - annotate_overrides
 ''',
       );
-      p.file('lib/main.dart.expect', '''
+      p!.file('lib/main.dart.expect', '''
 class A {
   String a() => '';
 }
 ''');
       result =
-          await runFix(['--compare-to-golden', '.'], workingDir: p.dirPath);
+          await runFix(['--compare-to-golden', '.'], workingDir: p!.dirPath);
       assertResult(exitCode: 1);
     });
   });
diff --git a/pkg/dartdev/test/commands/flag_test.dart b/pkg/dartdev/test/commands/flag_test.dart
index 3feab2de5f5..7c4b4fa5324 100644
--- a/pkg/dartdev/test/commands/flag_test.dart
+++ b/pkg/dartdev/test/commands/flag_test.dart
@@ -11,6 +11,7 @@ import 'package:test/test.dart';
 import '../utils.dart';
 
 void main() {
+  initGlobalState();
   group('command', command, timeout: longTimeout);
   group('flag', help, timeout: longTimeout);
 }
@@ -34,30 +35,28 @@ void command() {
     DartdevRunner(['--no-analytics'])
         .commands
         .forEach((String commandKey, Command command) {
-      if (command.argParser != null) {
-        if (command.name != 'help' &&
-            command.name != 'format' &&
-            command.name != 'pub' &&
-            command.name != 'test') {
-          expect(command.argParser.usageLineLength,
-              stdout.hasTerminal ? stdout.terminalColumns : null);
-        } else if (command.name == 'pub') {
-          // TODO(sigurdm): Avoid special casing here.
-          // https://github.com/dart-lang/pub/issues/2700
-          expect(command.argParser.usageLineLength,
-              stdout.hasTerminal ? stdout.terminalColumns : 80);
-        } else {
-          expect(command.argParser.usageLineLength, isNull);
-        }
+      if (command.name != 'help' &&
+          command.name != 'format' &&
+          command.name != 'pub' &&
+          command.name != 'test') {
+        expect(command.argParser.usageLineLength,
+            stdout.hasTerminal ? stdout.terminalColumns : null);
+      } else if (command.name == 'pub') {
+        // TODO(sigurdm): Avoid special casing here.
+        // https://github.com/dart-lang/pub/issues/2700
+        expect(command.argParser.usageLineLength,
+            stdout.hasTerminal ? stdout.terminalColumns : 80);
+      } else {
+        expect(command.argParser.usageLineLength, isNull);
       }
     });
   });
 }
 
 void help() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('--help', () async {
     p = project();
diff --git a/pkg/dartdev/test/commands/format_test.dart b/pkg/dartdev/test/commands/format_test.dart
index cf82970f403..2026f3f93f8 100644
--- a/pkg/dartdev/test/commands/format_test.dart
+++ b/pkg/dartdev/test/commands/format_test.dart
@@ -14,9 +14,9 @@ void main() {
 }
 
 void format() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('--help', () async {
     p = project();
diff --git a/pkg/dartdev/test/commands/help_test.dart b/pkg/dartdev/test/commands/help_test.dart
index 69f1f27286b..8aa3d74fccf 100644
--- a/pkg/dartdev/test/commands/help_test.dart
+++ b/pkg/dartdev/test/commands/help_test.dart
@@ -13,9 +13,9 @@ void main() {
 }
 
 void help() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   /// Commands not tested by the following loop.
   List<String> _commandsNotTested = <String>[
diff --git a/pkg/dartdev/test/commands/language_server_test.dart b/pkg/dartdev/test/commands/language_server_test.dart
index 543aec981a8..06d75dc9f8e 100644
--- a/pkg/dartdev/test/commands/language_server_test.dart
+++ b/pkg/dartdev/test/commands/language_server_test.dart
@@ -21,10 +21,10 @@ void main() {
 }
 
 void defineLanguageServerTests() {
-  utils.TestProject project;
-  Process process;
+  late utils.TestProject project;
+  Process? process;
 
-  tearDown(() async => await project?.dispose());
+  tearDown(() async => await project.dispose());
 
   Future runWithLsp(List<String> args) async {
     project = utils.project();
@@ -32,7 +32,7 @@ void defineLanguageServerTests() {
     process = await project.start(args);
 
     final Stream<String> inStream =
-        process.stdout.transform<String>(utf8.decoder);
+        process!.stdout.transform<String>(utf8.decoder);
 
     // Send an LSP init.
     final String message = jsonEncode({
@@ -47,9 +47,9 @@ void defineLanguageServerTests() {
       },
     });
 
-    process.stdin.write('Content-Length: ${message.length}\r\n');
-    process.stdin.write('\r\n');
-    process.stdin.write(message);
+    process!.stdin.write('Content-Length: ${message.length}\r\n');
+    process!.stdin.write('\r\n');
+    process!.stdin.write(message);
 
     List<String> responses = await inStream.take(2).toList();
     expect(responses, hasLength(2));
@@ -65,7 +65,7 @@ void defineLanguageServerTests() {
     final serverInfo = result['serverInfo'];
     expect(serverInfo['name'], isNotEmpty);
 
-    process.kill();
+    process!.kill();
     process = null;
   }
 
@@ -82,7 +82,7 @@ void defineLanguageServerTests() {
 
     process = await project.start(['language-server', '--protocol=analyzer']);
 
-    final Stream<String> inStream = process.stdout
+    final Stream<String> inStream = process!.stdout
         .transform<String>(utf8.decoder)
         .transform<String>(const LineSplitter());
 
@@ -95,7 +95,7 @@ void defineLanguageServerTests() {
     expect(params['version'], isNotEmpty);
     expect(params['pid'], isNot(0));
 
-    process.kill();
+    process!.kill();
     process = null;
   });
 }
diff --git a/pkg/dartdev/test/commands/migrate_test.dart b/pkg/dartdev/test/commands/migrate_test.dart
index 0b394ad9f19..24b06148b48 100644
--- a/pkg/dartdev/test/commands/migrate_test.dart
+++ b/pkg/dartdev/test/commands/migrate_test.dart
@@ -15,9 +15,9 @@ void defineMigrateTests() {
   final runPubGet = contains('Run `dart pub get`');
   final setLowerSdkConstraint = contains('Set the lower SDK constraint');
 
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('--help', () async {
     p = project();
diff --git a/pkg/dartdev/test/commands/pub_test.dart b/pkg/dartdev/test/commands/pub_test.dart
index f2486dd51f3..0c1131928f7 100644
--- a/pkg/dartdev/test/commands/pub_test.dart
+++ b/pkg/dartdev/test/commands/pub_test.dart
@@ -13,9 +13,9 @@ void main() {
 }
 
 void pub() {
-  TestProject p;
+  TestProject p = project();
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   void _assertPubHelpInvoked(ProcessResult result) {
     expect(result, isNotNull);
diff --git a/pkg/dartdev/test/commands/run_test.dart b/pkg/dartdev/test/commands/run_test.dart
index f3174c789f4..40978d9f22e 100644
--- a/pkg/dartdev/test/commands/run_test.dart
+++ b/pkg/dartdev/test/commands/run_test.dart
@@ -21,9 +21,9 @@ void main() {
 }
 
 void run() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('--help', () async {
     p = project();
@@ -345,7 +345,7 @@ void main(List<String> args) => print("$b $args");
     );
 
     expect(result.stdout,
-        predicate((o) => !'$o'.contains(soundNullSafetyMessage)));
+        predicate((dynamic o) => !'$o'.contains(soundNullSafetyMessage)));
     expect(result.stderr, isEmpty);
     expect(result.exitCode, 0);
   });
@@ -497,7 +497,7 @@ void main(List<String> args) => print("$b $args");
         final readyCompleter = Completer<void>();
         final completer = Completer<void>();
 
-        StreamSubscription sub;
+        late StreamSubscription sub;
         sub = process.stdout.transform(utf8.decoder).listen((event) async {
           if (event.contains('ready')) {
             readyCompleter.complete();
diff --git a/pkg/dartdev/test/commands/test_test.dart b/pkg/dartdev/test/commands/test_test.dart
index 7f758d30e42..1005862cae2 100644
--- a/pkg/dartdev/test/commands/test_test.dart
+++ b/pkg/dartdev/test/commands/test_test.dart
@@ -17,9 +17,9 @@ Future<void> main() async {
 }
 
 void defineTest(List<Experiment> experiments) {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('--help', () async {
     p = project();
@@ -152,7 +152,7 @@ void main() {
   });
 
   group('--enable-experiment', () {
-    Future<ProcessResult> runTestWithExperimentFlag(String flag) async {
+    Future<ProcessResult> runTestWithExperimentFlag(String? flag) async {
       return await p.run([
         if (flag != null) flag,
         'test',
@@ -162,7 +162,7 @@ void main() {
       ]);
     }
 
-    Future<void> expectSuccess(String flag) async {
+    Future<void> expectSuccess(String? flag) async {
       final result = await runTestWithExperimentFlag(flag);
       expect(result.stdout, contains('feature enabled'),
           reason: 'stderr: ${result.stderr}');
@@ -170,7 +170,7 @@ void main() {
           reason: 'stdout: ${result.stdout} stderr: ${result.stderr}');
     }
 
-    Future<void> expectFailure(String flag) async {
+    Future<void> expectFailure(String? flag) async {
       final result = await runTestWithExperimentFlag(flag);
       expect(result.exitCode, isNot(0));
     }
diff --git a/pkg/dartdev/test/core_test.dart b/pkg/dartdev/test/core_test.dart
index f9c8e293bb1..e06feef887b 100644
--- a/pkg/dartdev/test/core_test.dart
+++ b/pkg/dartdev/test/core_test.dart
@@ -18,6 +18,7 @@ import 'package:test/test.dart';
 import 'utils.dart';
 
 void main() {
+  initGlobalState();
   group('DartdevCommand', _dartdevCommand);
   group('PackageConfig', _packageConfig);
   group('Project', _project);
@@ -45,29 +46,35 @@ void _dartdevCommand() {
 
   test('compile/js', () {
     _assertDartdevCommandProperties(
-        CompileCommand().subcommands['js'], 'js', 'compile/js');
+        CompileCommand().subcommands['js'] as DartdevCommand,
+        'js',
+        'compile/js');
   });
 
   test('compile/jit-snapshot', () {
     _assertDartdevCommandProperties(
-        CompileCommand().subcommands['jit-snapshot'],
+        CompileCommand().subcommands['jit-snapshot'] as DartdevCommand,
         'jit-snapshot',
         'compile/jit-snapshot');
   });
 
   test('compile/kernel', () {
     _assertDartdevCommandProperties(
-        CompileCommand().subcommands['kernel'], 'kernel', 'compile/kernel');
+        CompileCommand().subcommands['kernel'] as DartdevCommand,
+        'kernel',
+        'compile/kernel');
   });
 
   test('compile/exe', () {
     _assertDartdevCommandProperties(
-        CompileCommand().subcommands['exe'], 'exe', 'compile/exe');
+        CompileCommand().subcommands['exe'] as DartdevCommand,
+        'exe',
+        'compile/exe');
   });
 
   test('compile/aot-snapshot', () {
     _assertDartdevCommandProperties(
-        CompileCommand().subcommands['aot-snapshot'],
+        CompileCommand().subcommands['aot-snapshot'] as DartdevCommand,
         'aot-snapshot',
         'compile/aot-snapshot');
   });
@@ -103,9 +110,9 @@ void _packageConfig() {
 }
 
 void _project() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('hasPubspecFile positive', () {
     p = project();
@@ -128,7 +135,7 @@ void _project() {
     Project coreProj = Project.fromDirectory(p.dir);
     expect(coreProj.hasPackageConfigFile, isTrue);
     expect(coreProj.packageConfig, isNotNull);
-    expect(coreProj.packageConfig.packages, isNotEmpty);
+    expect(coreProj.packageConfig!.packages, isNotEmpty);
   });
 
   test('hasPackageConfigFile negative', () {
diff --git a/pkg/dartdev/test/experiment_util.dart b/pkg/dartdev/test/experiment_util.dart
index 0cf98e1938d..4ad4ae47804 100644
--- a/pkg/dartdev/test/experiment_util.dart
+++ b/pkg/dartdev/test/experiment_util.dart
@@ -12,7 +12,7 @@ import 'package:yaml/yaml.dart' as yaml;
 /// associated `validation` program.
 Future<List<Experiment>> experimentsWithValidation() async {
   final url = (await Isolate.resolvePackageUri(
-          Uri.parse('package:dartdev/dartdev.dart')))
+          Uri.parse('package:dartdev/dartdev.dart')))!
       .resolve('../../../tools/experimental_features.yaml');
   final experiments =
       yaml.loadYaml(File.fromUri(url).readAsStringSync(), sourceUrl: url);
@@ -28,14 +28,14 @@ Future<List<Experiment>> experimentsWithValidation() async {
   ];
 }
 
-Version tryParseVersion(String version) =>
+Version? tryParseVersion(String? version) =>
     version == null ? null : Version.parse(version);
 
 class Experiment {
   final String name;
   final String validation;
-  final Version enabledIn;
-  final Version experimentalReleaseVersion;
+  final Version? enabledIn;
+  final Version? experimentalReleaseVersion;
   Experiment(
     this.name,
     this.validation,
diff --git a/pkg/dartdev/test/fix_driver_test.dart b/pkg/dartdev/test/fix_driver_test.dart
index 8b718044800..ac9a6e9b1c1 100644
--- a/pkg/dartdev/test/fix_driver_test.dart
+++ b/pkg/dartdev/test/fix_driver_test.dart
@@ -18,8 +18,8 @@ Future<FixOutput> runFix(List<String> args) async {
 }
 
 void _driver() {
-  TestProject p;
-  tearDown(() async => await p?.dispose());
+  late TestProject p;
+  tearDown(() async => await p.dispose());
 
   test('no fixes', () async {
     p = project(mainSrc: 'int get foo => 1;\n');
@@ -33,7 +33,7 @@ class FixOutput {
   final FixResult<CapturingLogger> result;
   FixOutput(this.result);
 
-  int get returnCode => result.returnCode;
+  int? get returnCode => result.returnCode;
   String get stderr => result.logger.output.stderr.toString();
   String get stdout => result.logger.output.stdout.toString();
 }
diff --git a/pkg/dartdev/test/load_from_dill_test.dart b/pkg/dartdev/test/load_from_dill_test.dart
index 0412854ad23..1c4542bffe1 100644
--- a/pkg/dartdev/test/load_from_dill_test.dart
+++ b/pkg/dartdev/test/load_from_dill_test.dart
@@ -9,9 +9,9 @@ import 'package:test/test.dart';
 import 'utils.dart';
 
 void main() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test("Fallback to dartdev.dill from dartdev.dart.snapshot for 'Hello World'",
       () async {
diff --git a/pkg/dartdev/test/no_such_file_test.dart b/pkg/dartdev/test/no_such_file_test.dart
index 549c059f206..1208a5e082e 100644
--- a/pkg/dartdev/test/no_such_file_test.dart
+++ b/pkg/dartdev/test/no_such_file_test.dart
@@ -7,9 +7,9 @@ import 'package:test/test.dart';
 import 'utils.dart';
 
 void main() {
-  TestProject p;
+  late TestProject p;
 
-  tearDown(() async => await p?.dispose());
+  tearDown(() async => await p.dispose());
 
   test('Ensure parsing fails after encountering invalid file', () async {
     // Regression test for https://github.com/dart-lang/sdk/issues/43991
diff --git a/pkg/dartdev/test/smoke/smoke.dart b/pkg/dartdev/test/smoke/smoke.dart
index 003118f5287..a6a518105cb 100644
--- a/pkg/dartdev/test/smoke/smoke.dart
+++ b/pkg/dartdev/test/smoke/smoke.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.10
-
 void main() {
   print('Smoke test!');
 }
diff --git a/pkg/dartdev/test/smoke/smoke_test.dart b/pkg/dartdev/test/smoke/smoke_test.dart
index 671836d614d..faad4839723 100644
--- a/pkg/dartdev/test/smoke/smoke_test.dart
+++ b/pkg/dartdev/test/smoke/smoke_test.dart
@@ -63,7 +63,7 @@ void main() {
         );
         expect(
           result.stderr,
-          'Could not start VM service: localhost:${server.port} is already in use.\n',
+          'Could not start the VM service: localhost:${server.port} is already in use.\n',
         );
         expect(result.stdout, isEmpty);
         server.close();
diff --git a/pkg/dartdev/test/utils.dart b/pkg/dartdev/test/utils.dart
index b45e60b2a1c..316c8bc26d6 100644
--- a/pkg/dartdev/test/utils.dart
+++ b/pkg/dartdev/test/utils.dart
@@ -5,6 +5,8 @@
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:cli_util/cli_logging.dart';
+import 'package:dartdev/src/core.dart';
 import 'package:path/path.dart' as path;
 import 'package:pub_semver/pub_semver.dart';
 import 'package:test/test.dart';
@@ -18,13 +20,17 @@ const Timeout longTimeout = Timeout(Duration(minutes: 5));
 /// version:
 const String dartVersionFilePrefix2_9 = '// @dart = 2.9\n';
 
+void initGlobalState() {
+  log = Logger.standard();
+}
+
 TestProject project(
-        {String mainSrc,
-        String analysisOptions,
+        {String? mainSrc,
+        String? analysisOptions,
         bool logAnalytics = false,
         String name = TestProject._defaultProjectName,
-        VersionConstraint sdkConstraint,
-        Map<String, dynamic> pubspec}) =>
+        VersionConstraint? sdkConstraint,
+        Map<String, dynamic>? pubspec}) =>
     TestProject(
         mainSrc: mainSrc,
         analysisOptions: analysisOptions,
@@ -35,7 +41,7 @@ TestProject project(
 class TestProject {
   static const String _defaultProjectName = 'dartdev_temp';
 
-  Directory dir;
+  late Directory dir;
 
   String get dirPath => dir.path;
 
@@ -47,19 +53,20 @@ class TestProject {
 
   final bool logAnalytics;
 
-  final VersionConstraint sdkConstraint;
+  final VersionConstraint? sdkConstraint;
 
-  final Map<String, dynamic> pubspec;
+  final Map<String, dynamic>? pubspec;
 
-  Process _process;
+  Process? _process;
 
   TestProject(
-      {String mainSrc,
-      String analysisOptions,
+      {String? mainSrc,
+      String? analysisOptions,
       this.name = _defaultProjectName,
       this.logAnalytics = false,
       this.sdkConstraint,
       this.pubspec}) {
+    initGlobalState();
     dir = Directory.systemTemp.createTempSync('a');
     file(
         'pubspec.yaml',
@@ -113,7 +120,7 @@ dev_dependencies:
 
   Future<ProcessResult> run(
     List<String> arguments, {
-    String workingDir,
+    String? workingDir,
   }) async {
     _process = await Process.start(
         Platform.resolvedExecutable,
@@ -123,11 +130,11 @@ dev_dependencies:
         ],
         workingDirectory: workingDir ?? dir.path,
         environment: {if (logAnalytics) '_DARTDEV_LOG_ANALYTICS': 'true'});
-    final stdoutContents = _process.stdout.transform(utf8.decoder).join();
-    final stderrContents = _process.stderr.transform(utf8.decoder).join();
-    final code = await _process.exitCode;
+    final stdoutContents = _process!.stdout.transform(utf8.decoder).join();
+    final stderrContents = _process!.stderr.transform(utf8.decoder).join();
+    final code = await _process!.exitCode;
     return ProcessResult(
-      _process.pid,
+      _process!.pid,
       code,
       await stdoutContents,
       await stderrContents,
@@ -136,7 +143,7 @@ dev_dependencies:
 
   Future<Process> start(
     List<String> arguments, {
-    String workingDir,
+    String? workingDir,
   }) {
     return Process.start(
         Platform.resolvedExecutable,
@@ -149,7 +156,7 @@ dev_dependencies:
       ..then((p) => _process = p);
   }
 
-  String _sdkRootPath;
+  String? _sdkRootPath;
 
   /// Return the root of the SDK.
   String get sdkRootPath {
@@ -161,24 +168,24 @@ dev_dependencies:
         if (File(path.join(tryDir, 'pkg', 'dartdev', 'bin', 'dartdev.dart'))
             .existsSync()) {
           _sdkRootPath = tryDir;
-          return _sdkRootPath;
+          return _sdkRootPath!;
         }
         current = tryDir;
       } while (path.dirname(current) != current);
       throw StateError('can not find SDK repository root');
     }
-    return _sdkRootPath;
+    return _sdkRootPath!;
   }
 
   String get absolutePathToDartdevFile =>
       path.join(sdkRootPath, 'pkg', 'dartdev', 'bin', 'dartdev.dart');
 
-  Directory findDirectory(String name) {
+  Directory? findDirectory(String name) {
     var directory = Directory(path.join(dir.path, name));
     return directory.existsSync() ? directory : null;
   }
 
-  File findFile(String name) {
+  File? findFile(String name) {
     var file = File(path.join(dir.path, name));
     return file.existsSync() ? file : null;
   }
diff --git a/pkg/dartdev/test/utils_test.dart b/pkg/dartdev/test/utils_test.dart
index 111326b0a92..83f2567cc35 100644
--- a/pkg/dartdev/test/utils_test.dart
+++ b/pkg/dartdev/test/utils_test.dart
@@ -64,7 +64,8 @@ void main() {
       List<dynamic> _packages = contents['packages'];
       try {
         // ignore: unused_local_variable
-        List<Map<String, dynamic>> packages = _packages;
+        List<Map<String, dynamic>> packages =
+            _packages as List<Map<String, dynamic>>;
         fail('expected implicit cast to fail');
       } on TypeError {
         // TypeError is expected
diff --git a/pkg/dartdev/tool/fix_driver.dart b/pkg/dartdev/tool/fix_driver.dart
index 17f246a0504..d2d8723f4f8 100644
--- a/pkg/dartdev/tool/fix_driver.dart
+++ b/pkg/dartdev/tool/fix_driver.dart
@@ -8,9 +8,8 @@ import 'package:cli_util/cli_logging.dart';
 import 'package:dartdev/src/commands/fix.dart';
 import 'package:dartdev/src/core.dart';
 import 'package:dartdev/src/utils.dart';
-import 'package:meta/meta.dart';
 
-Future<void> main(List<String> args) async {
+Future<int?> main(List<String> args) async {
   var runner = FixRunner(logger: Logger.standard());
   var result = await runner.runFix(args);
   return result.returnCode;
@@ -32,7 +31,7 @@ class CapturedProgress extends Progress {
   }
 
   @override
-  void finish({String message, bool showTiming = false}) {
+  void finish({String? message, bool showTiming = false}) {
     // todo (pq): consider capturing / tracking finish display updates.
     finished = true;
   }
@@ -85,7 +84,7 @@ class CapturingLogger implements Logger {
 
 class FixResult<T extends Logger> {
   /// The value returned by [FixCommand.run].
-  final int returnCode;
+  final int? returnCode;
 
   /// The logger used in driving fixes.
   final T logger;
@@ -104,7 +103,7 @@ class FixRunner<T extends Logger> extends CommandRunner<int> {
     allowTrailingOptions: false,
   );
 
-  FixRunner({@required this.logger})
+  FixRunner({required this.logger})
       : super('fix_runner',
             'A command-line utility for testing the `dart fix` command.') {
     addCommand(FixCommand());
@@ -112,14 +111,14 @@ class FixRunner<T extends Logger> extends CommandRunner<int> {
   }
 
   @override
-  Future<int> runCommand(ArgResults topLevelResults) async {
+  Future<int?> runCommand(ArgResults topLevelResults) async {
     var result = await super.runCommand(topLevelResults);
     return result;
   }
 
   Future<FixResult<T>> runFix(List<String> args) async {
     log = logger;
-    var argResults = argParser.parse(['fix', ...?args]);
+    var argResults = argParser.parse(['fix', ...args]);
     var result = await runCommand(argResults);
     return FixResult(logger, result);
   }
diff --git a/runtime/bin/dartdev_isolate.cc b/runtime/bin/dartdev_isolate.cc
index 4b9fe69004c..93259b05bf5 100644
--- a/runtime/bin/dartdev_isolate.cc
+++ b/runtime/bin/dartdev_isolate.cc
@@ -206,7 +206,7 @@ void DartDevIsolate::DartDevRunner::RunCallback(uword args) {
   Dart_IsolateFlags flags;
   Dart_IsolateFlagsInitialize(&flags);
   flags.enable_asserts = false;
-  flags.null_safety = false;
+  flags.null_safety = true;
   flags.use_field_guards = true;
   flags.use_osr = true;
   flags.is_system_isolate = true;
diff --git a/utils/dartdev/BUILD.gn b/utils/dartdev/BUILD.gn
index 3ce3bc38a15..e3818aaedf7 100644
--- a/utils/dartdev/BUILD.gn
+++ b/utils/dartdev/BUILD.gn
@@ -25,6 +25,7 @@ application_snapshot("generate_dartdev_kernel") {
   main_dart = "../../pkg/dartdev/bin/dartdev.dart"
   training_args = []
   deps = [ "../dds:dds" ]
+  vm_args = [ "--sound-null-safety" ]
   output = "$root_gen_dir/dartdev.dill"
 }
 
@@ -39,6 +40,7 @@ application_snapshot("generate_dartdev_snapshot") {
   main_dart = "../../pkg/dartdev/bin/dartdev.dart"
   training_args = [ "--help" ]
   deps = [ "../dds:dds" ]
+  vm_args = [ "--sound-null-safety" ]
   output = "$root_gen_dir/dartdev.dart.snapshot"
 }