[analyzer/cfe] Always use pre-built SDK for formatting generated files.

Change the following code paths so that they format Dart code by
running `tools/sdks/dart-sdk/bin/dart format` as a subprocess:

- `generate_messages.dart` (this is the CFE tool that generates
  `pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart` and
  `pkg/front_end/lib/src/codes/cfe_codes_generated.dart`).

- `generated_files_up_to_date_git_test.dart` (this is a CFE test that
  verifies that
  `pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart` and
  `pkg/front_end/lib/src/codes/cfe_codes_generated.dart` are up to
  date).

- `GeneratedFile.generate` (this is the common method used by most
  analyzer code generators).

- `GeneratedContentExtension.check` (this is used by analyzer tests to
  verify that generated files are up to date).

- `relevance_table_generator.dart` (this is an `analysis_server` tool
  that generates `relevance_tables*.g.dart` files).

Previously, these tools were inconsistent; some of them invoked the
formatter through its Dart API, and some of them ran `dart format` as
a subprocess via whatever `dart` executable was currently being used
for the parent process. This led to a risk that a generated file might
be immediately rejected by its own "up to date" test, or by the
presubmit script. Standardizing on the use of
`tools/sdks/dart-sdk/bin/dart format` (which is what the presubmit
script uses) should address this risk.

Addresses code review comments:
https://dart-review.googlesource.com/c/sdk/+/447920/comment/e9e1aa39_6fffc7e5/.

Change-Id: I6a6a69643a69505dc6e30547e0e784358458c357
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/448161
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Jens Johansen <jensj@google.com>

pkg/analyzer_utilities/lib/generated_content_check.dart

@@ -2,7 +2,6 @@ import 'dart:async';
 import 'dart:io';
 
 import 'package:analyzer_utilities/tools.dart';
-import 'package:dart_style/dart_style.dart';
 import 'package:package_config/package_config.dart';
 import 'package:path/path.dart';
 import 'package:pub_semver/pub_semver.dart';
@@ -27,7 +26,7 @@ Future<String> _formatText(String text, {required String pkgPath}) async {
     throw StateError('Could not find a Dart language version for "$pkgPath"');
   }
   var version = Version(languageVersion.major, languageVersion.minor, 0);
-  return DartFormatter(languageVersion: version).format(text);
+  return DartFormat.formatString(text, languageVersion: version);
 }
 
 extension GeneratedContentExtension on GeneratedContent {

pkg/analyzer_utilities/lib/tools.dart

@@ -8,11 +8,13 @@ library;
 import 'dart:async';
 import 'dart:io';
 
+import 'package:analyzer_testing/package_root.dart';
 import 'package:analyzer_utilities/html_dom.dart' as dom;
 import 'package:analyzer_utilities/html_generator.dart';
 import 'package:analyzer_utilities/text_formatter.dart';
 import 'package:collection/collection.dart';
 import 'package:path/path.dart';
+import 'package:pub_semver/pub_semver.dart';
 
 final RegExp trailingSpacesInLineRegExp = RegExp(r' +$', multiLine: true);
 final RegExp trailingWhitespaceRegExp = RegExp(r'[\n ]+$');
@@ -243,13 +245,33 @@ class CodeGeneratorSettings {
 
 /// A utility class for invoking 'dart format'.
 class DartFormat {
-  static String get _dartPath => Platform.resolvedExecutable;
+  static final String _dartPath =
+      // TODO(paulberry): check that this is the right path on Windows.
+      join(packageRoot, '..', 'tools', 'sdks', 'dart-sdk', 'bin', 'dart');
 
   static void formatFile(File file) {
     var result = Process.runSync(_dartPath, ['format', file.path]);
     _throwIfExitCode(result);
   }
 
+  static String formatString(String text, {required Version languageVersion}) {
+    var tempDir = Directory.systemTemp.createTempSync('format');
+    try {
+      var file = File(join(tempDir.path, 'input.dart'));
+      file.writeAsStringSync(text);
+      var result = Process.runSync(_dartPath, [
+        'format',
+        file.path,
+        '--language-version',
+        '${languageVersion.major}.${languageVersion.minor}',
+      ]);
+      _throwIfExitCode(result);
+      return file.readAsStringSync();
+    } finally {
+      tempDir.deleteSync(recursive: true);
+    }
+  }
+
   static void _throwIfExitCode(ProcessResult result) {
     if (result.exitCode != 0) throw result.stderr as Object;
   }

pkg/analyzer_utilities/pubspec.yaml

@@ -10,8 +10,8 @@ resolution: workspace
 # Use 'any' constraints here; we get our versions from the DEPS file.
 dependencies:
   analyzer: any
+  analyzer_testing: any
   collection: any
-  dart_style: any
   package_config: any
   path: any
   pub_semver: any

pkg/front_end/test/generated_files_up_to_date_git_test.dart

@@ -4,7 +4,7 @@
 
 import "dart:io" show File, exitCode;
 
-import 'package:dart_style/dart_style.dart' show DartFormatter;
+import "package:analyzer_utilities/tools.dart" show DartFormat;
 
 import "../tool/generate_experimental_flags.dart" as generateExperimentalFlags;
 import "../tool/generate_messages.dart" as generateMessages;
@@ -133,18 +133,20 @@ void messages() {
 
   Uri generatedFile = generateMessages.computeSharedGeneratedFile(repoDir);
   check(
-    new DartFormatter(
+    DartFormat.formatString(
+      messages.sharedMessages,
       languageVersion: getPackageVersionFor('_fe_analyzer_shared'),
-    ).format(messages.sharedMessages),
+    ),
     generatedFile,
     "dart pkg/front_end/tool/generate_messages.dart",
   );
 
   Uri cfeGeneratedFile = generateMessages.computeCfeGeneratedFile(repoDir);
   check(
-    new DartFormatter(
+    DartFormat.formatString(
+      messages.cfeMessages,
       languageVersion: getPackageVersionFor('front_end'),
-    ).format(messages.cfeMessages),
+    ),
     cfeGeneratedFile,
     "dart pkg/front_end/tool/generate_messages.dart",
   );