[dartdev] Implement --enable-experiments for dart run and dart pub run.

Related to https://github.com/dart-lang/sdk/issues/42339.

Change-Id: I3fdeee33dcad0ca031f483e2e3692be300392958
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/152960
Reviewed-by: Jaime Wren <jwren@google.com>
Commit-Queue: Devon Carew <devoncarew@google.com>

pkg/analyzer/lib/source/line_info.dart

@@ -47,8 +47,7 @@ class LineInfo {
   /// Return the location information for the character at the given [offset].
   ///
   /// A future version of this API will return a [CharacterLocation] rather than
-  /// // ignore: deprecated_member_use_from_same_package
-  /// a [LineInfo_Location].
+  /// a [LineInfo_Location]. // ignore: deprecated_member_use_from_same_package
   // ignore: deprecated_member_use_from_same_package
   LineInfo_Location getLocation(int offset) {
     var min = 0;

pkg/analyzer/lib/src/dart/analysis/experiments.dart

@@ -33,7 +33,7 @@ class ExperimentStatus with _CurrentState implements FeatureSet {
   static final Version currentVersion = Version.parse(_currentVersion);
 
   /// A map containing information about all known experimental flags.
-  static const knownFeatures = _knownFeatures;
+  static const Map<String, ExperimentalFeature> knownFeatures = _knownFeatures;
 
   final List<bool> _enableFlags;
 

pkg/analyzer/lib/src/dart/analysis/experiments.g.dart

@@ -125,7 +125,7 @@ class ExperimentalFeatures {
     enableString: EnableString.nonfunction_type_aliases,
     isEnabledByDefault: IsEnabledByDefault.nonfunction_type_aliases,
     isExpired: IsExpired.nonfunction_type_aliases,
-    documentation: 'Type aliases define a <type>, not just a <functionType>.',
+    documentation: 'Type aliases define a <type>, not just a <functionType>',
     firstSupportedVersion: null,
   );
 
@@ -161,7 +161,7 @@ class ExperimentalFeatures {
     enableString: EnableString.variance,
     isEnabledByDefault: IsEnabledByDefault.variance,
     isExpired: IsExpired.variance,
-    documentation: 'Sound variance.',
+    documentation: 'Sound variance',
     firstSupportedVersion: null,
   );
 

pkg/dartdev/lib/dartdev.dart

@@ -4,6 +4,7 @@
 
 import 'dart:io' as io;
 
+import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:cli_util/cli_logging.dart';
@@ -19,13 +20,14 @@ import 'src/commands/pub.dart';
 import 'src/commands/run.dart';
 import 'src/commands/test.dart';
 import 'src/core.dart';
+import 'src/experiments.dart';
 
 /// This is typically called from bin/, but given the length of the method and
 /// analytics logic, it has been moved here. Also note that this method calls
 /// [io.exit(code)] directly.
 Future<void> runDartdev(List<String> args) async {
   final stopwatch = Stopwatch();
-  dynamic result;
+  int result;
 
   // The Analytics instance used to report information back to Google Analytics,
   // see lib/src/analytics.dart.
@@ -104,7 +106,7 @@ Future<void> runDartdev(List<String> args) async {
     stopwatch.stop();
 
     // Set the exitCode, if it wasn't set in the catch block above.
-    exitCode ??= result is int ? result : 0;
+    exitCode ??= result ?? 0;
 
     // Send analytics before exiting
     if (analytics.enabled) {
@@ -151,8 +153,7 @@ class DartdevRunner<int> extends CommandRunner {
     argParser.addFlag('disable-analytics',
         negatable: false, help: 'Disable anonymous analytics.');
 
-    // TODO(jwren): hook up.
-    argParser.addMultiOption('enable-experiment', hide: true);
+    addExperimentalFlags(argParser, verbose);
 
     // A hidden flag to disable analytics on this run, this constructor can be
     // called with this flag, but should be removed before run() is called as
@@ -179,6 +180,7 @@ class DartdevRunner<int> extends CommandRunner {
   @override
   Future<int> runCommand(ArgResults topLevelResults) async {
     assert(!topLevelResults.arguments.contains('--disable-dartdev-analytics'));
+
     if (topLevelResults.command == null &&
         topLevelResults.arguments.isNotEmpty) {
       final firstArg = topLevelResults.arguments.first;
@@ -195,6 +197,37 @@ class DartdevRunner<int> extends CommandRunner {
     final Ansi ansi = Ansi(Ansi.terminalSupportsAnsi);
     log = isVerbose ? Logger.verbose(ansi: ansi) : Logger.standard(ansi: ansi);
 
+    if (wereExperimentsSpecified(topLevelResults)) {
+      List<String> experimentIds = specifiedExperiments(topLevelResults);
+      for (ExperimentalFeature feature in experimentalFeatures) {
+        // We allow default true flags, but complain when they are passed in.
+        if (feature.isEnabledByDefault &&
+            experimentIds.contains(feature.enableString)) {
+          print("'${feature.enableString}' is now enabled by default; this "
+              'flag is no longer required.');
+        }
+      }
+    }
+
     return await super.runCommand(topLevelResults);
   }
+
+  void addExperimentalFlags(ArgParser argParser, bool verbose) {
+    List<ExperimentalFeature> features = experimentalFeatures;
+
+    Map<String, String> allowedHelp = {};
+    for (ExperimentalFeature feature in features) {
+      String suffix =
+          feature.isEnabledByDefault ? ' (no-op - enabled by default)' : '';
+      allowedHelp[feature.enableString] = '${feature.documentation}$suffix';
+    }
+
+    argParser.addMultiOption(
+      experimentFlagName,
+      valueHelp: 'experiment',
+      allowed: features.map((feature) => feature.enableString),
+      allowedHelp: verbose ? allowedHelp : null,
+      help: 'Enable one or more experimental features.',
+    );
+  }
 }

pkg/dartdev/lib/src/commands/analyze.dart

@@ -12,6 +12,8 @@ import '../sdk.dart';
 import '../utils.dart';
 import 'analyze_impl.dart';
 
+// TODO: Support enable-experiment for 'dart analyze'.
+
 class AnalyzeCommand extends DartdevCommand<int> {
   AnalyzeCommand({bool verbose = false})
       : super('analyze', "Analyze the project's Dart code.") {

pkg/dartdev/lib/src/commands/pub.dart

@@ -8,6 +8,7 @@ import 'dart:io';
 import 'package:args/args.dart';
 
 import '../core.dart';
+import '../experiments.dart';
 import '../sdk.dart';
 
 class PubCommand extends DartdevCommand<int> {
@@ -42,7 +43,26 @@ class PubCommand extends DartdevCommand<int> {
   @override
   FutureOr<int> run() async {
     final command = sdk.pub;
-    final args = argResults.arguments;
+    var args = argResults.arguments;
+
+    // Pass any --enable-experiment options along.
+    if (args.isNotEmpty && wereExperimentsSpecified(globalResults)) {
+      List<String> experimentIds = specifiedExperiments(globalResults);
+
+      if (args.first == 'run') {
+        args = [
+          ...args.sublist(0, 1),
+          '--$experimentFlagName=${experimentIds.join(',')}',
+          ...args.sublist(1),
+        ];
+      } else if (args.length > 1 && args[0] == 'global' && args[0] == 'run') {
+        args = [
+          ...args.sublist(0, 2),
+          '--$experimentFlagName=${experimentIds.join(',')}',
+          ...args.sublist(2),
+        ];
+      }
+    }
 
     log.trace('$command ${args.join(' ')}');
 

pkg/dartdev/lib/src/commands/run.dart

@@ -11,6 +11,7 @@ import 'package:dds/dds.dart';
 import 'package:path/path.dart';
 
 import '../core.dart';
+import '../experiments.dart';
 import '../sdk.dart';
 import '../utils.dart';
 
@@ -55,7 +56,7 @@ Run a Dart file.''');
   @override
   FutureOr<int> run() async {
     // The command line arguments after 'run'
-    final args = argResults.arguments.toList();
+    var args = argResults.arguments.toList();
 
     var argsContainFileOrHelp = false;
     for (var arg in args) {
@@ -70,6 +71,7 @@ Run a Dart file.''');
     }
 
     final cwd = Directory.current;
+
     if (!argsContainFileOrHelp && cwd.existsSync()) {
       var foundImplicitFileToRun = false;
       var cwdName = cwd.name;
@@ -90,6 +92,7 @@ Run a Dart file.''');
           break;
         }
       }
+
       if (!foundImplicitFileToRun) {
         log.stderr(
           'Could not find the implicit file to run: '
@@ -98,6 +101,16 @@ Run a Dart file.''');
       }
     }
 
+    // Pass any --enable-experiment options along.
+    // todo: test
+    if (args.isNotEmpty && wereExperimentsSpecified(globalResults)) {
+      List<String> experimentIds = specifiedExperiments(globalResults);
+      args = [
+        '--$experimentFlagName=${experimentIds.join(',')}',
+        ...args,
+      ];
+    }
+
     // 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
     // service intermediary which implements the VM service protocol and
@@ -107,14 +120,14 @@ Run a Dart file.''');
         element.startsWith('--observe') ||
         element.startsWith('--enable-vm-service'))) {
       return await _DebuggingSession(this, args).start();
+    } else {
+      // Starting in ProcessStartMode.inheritStdio mode means the child process
+      // can detect support for ansi chars.
+      final process = await Process.start(
+          sdk.dart, ['--disable-dart-dev', ...args],
+          mode: ProcessStartMode.inheritStdio);
+      return process.exitCode;
     }
-
-    // Starting in ProcessStartMode.inheritStdio mode means the child process
-    // can detect support for ansi chars.
-    final process = await Process.start(
-        sdk.dart, ['--disable-dart-dev', ...args],
-        mode: ProcessStartMode.inheritStdio);
-    return process.exitCode;
   }
 }
 

pkg/dartdev/lib/src/experiments.dart

@@ -0,0 +1,25 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// 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:analyzer/src/dart/analysis/experiments.dart';
+import 'package:args/args.dart';
+
+const experimentFlagName = 'enable-experiment';
+
+/// Return a list of all the non-expired Dart experiments.
+List<ExperimentalFeature> get experimentalFeatures {
+  List<ExperimentalFeature> features = ExperimentStatus.knownFeatures.values
+      .where((feature) => !feature.isExpired)
+      .toList();
+  features.sort((a, b) => a.enableString.compareTo(b.enableString));
+  return features;
+}
+
+/// Return whether any Dart experiments were specified by the user.
+bool wereExperimentsSpecified(ArgResults argResults) =>
+    argResults.wasParsed(experimentFlagName);
+
+/// Return the list of Dart experiment flags specified by the user.
+List<String> specifiedExperiments(ArgResults argResults) =>
+    argResults[experimentFlagName];

pkg/dartdev/test/commands/flag_test.dart

@@ -2,6 +2,7 @@
 // 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:args/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:dartdev/dartdev.dart';
 import 'package:test/test.dart';
@@ -37,6 +38,17 @@ void command() {
       }
     });
   });
+
+  test('enable experiments flag is supported', () {
+    final args = [
+      '--disable-dartdev-analytics',
+      '--enable-experiment=non-nullable'
+    ];
+    final runner = DartdevRunner(args);
+    ArgResults results = runner.parse(args);
+    expect(results['enable-experiment'], isNotEmpty);
+    expect(results['enable-experiment'].first, 'non-nullable');
+  });
 }
 
 void help() {

pkg/dartdev/test/commands/pub_test.dart

@@ -34,6 +34,44 @@ void pub() {
     expect(result.stderr, isEmpty);
   });
 
+  test('--enable-experiment pub run', () {
+    p = project();
+    p.file('bin/main.dart',
+        "void main() { int a; a = null; print('a is \$a.'); }");
+
+    // run 'pub get'
+    p.runSync('pub', ['get']);
+
+    var result = p.runSync(
+        '--enable-experiment=non-nullable', ['pub', 'run', 'main.dart']);
+
+    expect(result.exitCode, 254);
+    expect(result.stdout, isEmpty);
+    expect(
+        result.stderr,
+        contains("A value of type 'Null' can't be assigned to a variable of "
+            "type 'int'"));
+  });
+
+  test('pub run --enable-experiment', () {
+    p = project();
+    p.file('bin/main.dart',
+        "void main() { int a; a = null; print('a is \$a.'); }");
+
+    // run 'pub get'
+    p.runSync('pub', ['get']);
+
+    var result = p.runSync(
+        'pub', ['run', '--enable-experiment=non-nullable', 'main.dart']);
+
+    expect(result.exitCode, 254);
+    expect(result.stdout, isEmpty);
+    expect(
+        result.stderr,
+        contains("A value of type 'Null' can't be assigned to a variable of "
+            "type 'int'"));
+  });
+
   test('failure', () {
     p = project(mainSrc: 'int get foo => 1;\n');
     var result = p.runSync('pub', ['deps']);

pkg/dartdev/test/commands/run_test.dart

@@ -36,6 +36,20 @@ void run() {
     expect(result.exitCode, 0);
   });
 
+  test('--enable-experiment', () {
+    p = project();
+    p.file('main.dart', "void main() { int a; a = null; print('a is \$a.'); }");
+    var result =
+        p.runSync('--enable-experiment=non-nullable', ['run', 'main.dart']);
+
+    expect(result.exitCode, 254);
+    expect(result.stdout, isEmpty);
+    expect(
+        result.stderr,
+        contains("A value of type 'Null' can't be assigned to a variable of "
+            "type 'int'"));
+  });
+
   test('no such file', () {
     p = project(mainSrc: "void main() { print('Hello World'); }");
     ProcessResult result =
@@ -47,7 +61,7 @@ void run() {
 
   test('implicit packageName.dart', () {
     // TODO(jwren) circle back to reimplement this test if possible, the file
-    //  name (package name) will be the name of the temporary directory on disk
+    // name (package name) will be the name of the temporary directory on disk
     p = project(mainSrc: "void main() { print('Hello World'); }");
     p.file('bin/main.dart', "void main() { print('Hello main.dart'); }");
     ProcessResult result = p.runSync('run', []);
@@ -57,7 +71,7 @@ void run() {
     expect(result.exitCode, 0);
   }, skip: true);
 
-  //Could not find the implicit file to run: bin
+  // Could not find the implicit file to run: bin
   test('missing implicit packageName.dart', () {
     p = project(mainSrc: "void main() { print('Hello World'); }");
     p.file('bin/foo.dart', "void main() { print('Hello main.dart'); }");

pkg/dartdev/test/experiments_test.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// 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:dartdev/src/experiments.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('experiments', () {
+    test('experimentalFeatures', () {
+      expect(experimentalFeatures, isNotEmpty);
+      expect(
+        experimentalFeatures.map((experiment) => experiment.enableString),
+        contains('non-nullable'),
+      );
+    });
+  });
+}

tools/experimental_features.yaml

@@ -95,13 +95,13 @@ features:
     help: "Triple-shift operator"
 
   variance:
-    help: "Sound variance."
+    help: "Sound variance"
 
   nonfunction-type-aliases:
-    help: "Type aliases define a <type>, not just a <functionType>."
+    help: "Type aliases define a <type>, not just a <functionType>"
 
   alternative-invalidation-strategy:
-    help: "Alternative invalidation strategy for incremental compilation."
+    help: "Alternative invalidation strategy for incremental compilation"
     category: "CFE"
 
 #