Add commands to swap dart imports for local development (#31925)

packages/flutter_tools/bin/web_swap.dart

+// Copyright 2019 The Chromium Authors. 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:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/context_runner.dart';
+import 'package:flutter_tools/src/globals.dart';
+import 'package:flutter_tools/src/runner/flutter_command_runner.dart';
+
+final ArgParser argParser = ArgParser()
+  ..addFlag('back', help: 'Swap back to dart:ui from web_ui', defaultsTo: false);
+
+/// Swap the dart:ui imports with web_ui for local development.
+///
+/// This is only intended as a temporary bridge to the new development
+/// workflow and will be removed at a later time.
+Future<void> main(List<String> arguments) async {
+  final ArgResults results = argParser.parse(arguments);
+  await runInContext(() {
+    // Normally this is initialized by the command runner.
+    Cache.flutterRoot = FlutterCommandRunner.defaultFlutterRoot;
+    printError(
+      'WARNING: This is only intended for use by flutter contributors.'
+      ' Running this command will alter the code in your flutter checkout.'
+    );
+    final String engineDirectory = fs.path.join(Cache.flutterRoot, '..', 'engine', 'src', 'flutter', 'lib', 'stub_ui');
+    final String flutterPath = fs.path.join(Cache.flutterRoot, 'packages', 'flutter');
+    final String flutterTestPath = fs.path.join(Cache.flutterRoot, 'packages', 'flutter_test');
+    final List<List<Pattern>> codePatterns = <List<Pattern>>[
+      <Pattern>['import \'dart:ui\'', 'import \'package:flutter_web_ui/ui.dart\''],
+      <Pattern>['export \'dart:ui\'', 'export \'package:flutter_web_ui/ui.dart\''],
+      <Pattern>[
+        'export \'bitfield.dart\' if (dart.library.html) \'bitfield_unsupported.dart\';',
+        'export \'bitfield_unsupported.dart\';'
+      ]
+    ];
+    final List<List<Pattern>> configPatterns = <List<Pattern>>[
+      <Pattern>[
+'''
+sky_engine:
+  sdk: flutter
+''',
+'''
+flutter_web_ui:
+  path: $engineDirectory
+'''
+      ],
+      <Pattern>[
+'''
+flutter:
+  sdk: flutter
+''',
+'''
+flutter:
+  path: $flutterPath
+'''
+      ],
+      <Pattern>[
+'''
+flutter_driver:
+  sdk: flutter
+''',
+'''
+#  flutter_driver:
+#    sdk: flutter
+'''
+      ],
+      <Pattern>[
+'''
+flutter_test:
+  sdk: flutter
+''',
+'''
+flutter_test:
+  path: $flutterTestPath
+build_runner: '>=0.8.10 <2.0.0'
+build_web_compilers: '>=0.3.6 <2.0.0'
+  '''
+      ],
+      <Pattern>[
+r'''
+flutter_goldens:
+  sdk: flutter
+''',
+r'''
+#  flutter_goldens:
+#    sdk: flutter
+'''
+      ],
+    ];
+
+    final Iterable<File> searchFiles = <Directory>[
+      fs.directory(fs.path.join(Cache.flutterRoot, 'packages')),
+      fs.directory(fs.path.join(Cache.flutterRoot, 'examples')),
+    ].expand((Directory directory) => directory.listSync(recursive: true))
+      .whereType<File>()
+      .where((File file) => file.path.endsWith('.dart') || file.path.endsWith('pubspec.yaml'));
+
+    for (File file in searchFiles) {
+      String contents = file.readAsStringSync();
+      final List<List<Pattern>> patterns = file.path.endsWith('.dart')
+          ? codePatterns
+          : configPatterns;
+      if (file.path.endsWith('.dart')) {
+        for (List<Pattern> patterns in patterns) {
+          contents = results['back']
+              ? contents.replaceAll(patterns.last, patterns.first)
+              : contents.replaceAll(patterns.first, patterns.last);
+        }
+        file.writeAsStringSync(contents);
+      }
+    }
+  });
+}
\ No newline at end of file

packages/flutter_tools/lib/src/runner/flutter_command_runner.dart

@@ -178,7 +178,7 @@ class FlutterCommandRunner extends CommandRunner<void> {
     return  '${wrapText(description)}\n\n$usageWithoutDescription';
   }
 
-  static String get _defaultFlutterRoot {
+  static String get defaultFlutterRoot {
     if (platform.environment.containsKey(kFlutterRootEnvironmentVariableName))
       return platform.environment[kFlutterRootEnvironmentVariableName];
     try {
@@ -342,7 +342,7 @@ class FlutterCommandRunner extends CommandRunner<void> {
 
     // We must set Cache.flutterRoot early because other features use it (e.g.
     // enginePath's initializer uses it).
-    final String flutterRoot = topLevelResults['flutter-root'] ?? _defaultFlutterRoot;
+    final String flutterRoot = topLevelResults['flutter-root'] ?? defaultFlutterRoot;
     Cache.flutterRoot = fs.path.normalize(fs.path.absolute(flutterRoot));
 
     // Set up the tooling configuration.
@@ -478,7 +478,7 @@ class FlutterCommandRunner extends CommandRunner<void> {
   }
 
   static void initFlutterRoot() {
-    Cache.flutterRoot ??= _defaultFlutterRoot;
+    Cache.flutterRoot ??= defaultFlutterRoot;
   }
 
   /// Get the root directories of the repo - the directories containing Dart packages.