[flutter_conductor] Add candidates sub command (#81234)

dev/tools/bin/conductor.dart

@@ -9,6 +9,7 @@
 import 'dart:io' as io;
 
 import 'package:args/command_runner.dart';
+import 'package:dev_tools/candidates.dart';
 import 'package:dev_tools/clean.dart';
 import 'package:dev_tools/codesign.dart';
 import 'package:dev_tools/globals.dart';
@@ -66,6 +67,10 @@ Future<void> main(List<String> args) async {
     CleanCommand(
       checkouts: checkouts,
     ),
+    CandidatesCommand(
+      checkouts: checkouts,
+      flutterRoot: localFlutterRoot,
+    ),
   ].forEach(runner.addCommand);
 
   if (!assertsEnabled()) {

dev/tools/lib/candidates.dart

+// Copyright 2014 The Flutter 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:args/command_runner.dart';
+import 'package:file/file.dart';
+
+import './git.dart';
+import './globals.dart' show releaseCandidateBranchRegex;
+import './repository.dart';
+import './stdio.dart';
+import './version.dart';
+
+const String kRemote = 'remote';
+
+class CandidatesCommand extends Command<void> {
+  CandidatesCommand({
+    required this.flutterRoot,
+    required this.checkouts,
+  }) : git = Git(checkouts.processManager), stdio = checkouts.stdio {
+    argParser.addOption(
+      kRemote,
+      help: 'Which remote name to query for branches.',
+      defaultsTo: 'upstream',
+    );
+  }
+
+  final Checkouts checkouts;
+  final Directory flutterRoot;
+  final Git git;
+  final Stdio stdio;
+
+  @override
+  String get name => 'candidates';
+
+  @override
+  String get description => 'List release candidates.';
+
+  @override
+  void run() {
+    final ArgResults results = argResults!;
+    git.run(
+      <String>['fetch', results[kRemote] as String],
+      'Fetch from remote ${results[kRemote]}',
+      workingDirectory: flutterRoot.path,
+    );
+
+    final FrameworkRepository framework = HostFrameworkRepository(
+      checkouts: checkouts,
+      name: 'framework-for-candidates',
+      upstreamPath: flutterRoot.path,
+    );
+
+    final Version currentVersion = framework.flutterVersion();
+    stdio.printStatus('currentVersion = $currentVersion');
+
+    final List<String> branches = git.getOutput(
+      <String>[
+        'branch',
+        '--no-color',
+        '--remotes',
+        '--list',
+        '${results[kRemote]}/*',
+      ],
+      'List all remote branches',
+      workingDirectory: flutterRoot.path,
+    ).split('\n');
+
+    // Pattern for extracting only the branch name via sub-group 1
+    final RegExp remotePattern = RegExp('${results[kRemote]}\\/(.*)');
+    for (final String branchName in branches) {
+      final RegExpMatch? candidateMatch = releaseCandidateBranchRegex.firstMatch(branchName);
+      if (candidateMatch == null) {
+        continue;
+      }
+      final int currentX = currentVersion.x;
+      final int currentY = currentVersion.y;
+      final int currentZ = currentVersion.z;
+      final int currentM = currentVersion.m ?? 0;
+      final int x = int.parse(candidateMatch.group(1)!);
+      final int y = int.parse(candidateMatch.group(2)!);
+      final int m = int.parse(candidateMatch.group(3)!);
+
+      final RegExpMatch match = remotePattern.firstMatch(branchName)!;
+      if (x < currentVersion.x) {
+        continue;
+      }
+      if (x == currentVersion.x && y < currentVersion.y) {
+        continue;
+      }
+      if (x == currentX && y == currentY && currentZ == 0 && m < currentM) {
+        continue;
+      }
+      stdio.printStatus(match.group(1)!);
+    }
+  }
+}

dev/tools/lib/repository.dart

@@ -519,6 +519,75 @@ class FrameworkRepository extends Repository {
   }
 }
 
+/// A wrapper around the host repository that is executing the conductor.
+///
+/// [Repository] methods that mutate the underlying repository will throw a
+/// [ConductorException].
+class HostFrameworkRepository extends FrameworkRepository {
+  HostFrameworkRepository({
+    required Checkouts checkouts,
+    String name = 'host-framework',
+    bool useExistingCheckout = false,
+    required String upstreamPath,
+  }) : super(
+    checkouts,
+    name: name,
+    fetchRemote: Remote(
+      name: RemoteName.upstream,
+      url: 'file://$upstreamPath/',
+    ),
+    localUpstream: false,
+    useExistingCheckout: useExistingCheckout,
+  ) {
+    _checkoutDirectory = checkouts.fileSystem.directory(upstreamPath);
+  }
+
+  @override
+  Directory get checkoutDirectory => _checkoutDirectory!;
+
+  @override
+  void newBranch(String branchName) {
+    throw ConductorException('newBranch not implemented for the host repository');
+  }
+
+  @override
+  void checkout(String ref) {
+    throw ConductorException('checkout not implemented for the host repository');
+  }
+
+  @override
+  String cherryPick(String commit) {
+    throw ConductorException('cherryPick not implemented for the host repository');
+  }
+
+  @override
+  String reset(String ref) {
+    throw ConductorException('reset not implemented for the host repository');
+  }
+
+  @override
+  void tag(String commit, String tagName, String remote) {
+    throw ConductorException('tag not implemented for the host repository');
+  }
+
+  @override
+  void updateChannel(
+    String commit,
+    String remote,
+    String branch, {
+    bool force = false,
+  }) {
+    throw ConductorException('updateChannel not implemented for the host repository');
+  }
+
+  @override
+  String authorEmptyCommit([String message = 'An empty commit']) {
+    throw ConductorException(
+      'authorEmptyCommit not implemented for the host repository',
+    );
+  }
+}
+
 class EngineRepository extends Repository {
   EngineRepository(
     this.checkouts, {

dev/tools/test/candidates_test.dart

+// Copyright 2014 The Flutter 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/command_runner.dart';
+import 'package:dev_tools/candidates.dart';
+import 'package:dev_tools/repository.dart';
+import 'package:file/memory.dart';
+import 'package:platform/platform.dart';
+
+import '../../../packages/flutter_tools/test/src/fake_process_manager.dart';
+import './common.dart';
+
+void main() {
+  group('candidates command', () {
+    const String flutterRoot = '/flutter';
+    const String flutterBinPath = '$flutterRoot/bin/flutter';
+    const String checkoutsParentDirectory = '$flutterRoot/dev/tools/';
+    const String remoteName = 'origin';
+
+    late MemoryFileSystem fileSystem;
+    late FakePlatform platform;
+    late TestStdio stdio;
+    late FakeProcessManager processManager;
+    final String operatingSystem = const LocalPlatform().operatingSystem;
+
+    setUp(() {
+      stdio = TestStdio();
+      fileSystem = MemoryFileSystem.test();
+    });
+
+    CommandRunner<void> createRunner({
+      required Checkouts checkouts,
+    }) {
+      final CandidatesCommand command = CandidatesCommand(
+        checkouts: checkouts,
+        flutterRoot: fileSystem.directory(flutterRoot),
+      );
+      return CommandRunner<void>('clean-test', '')..addCommand(command);
+    }
+
+    test('prints only branches from targeted remote', () async {
+      const String currentVersion = '1.2.3';
+      const String branch = 'flutter-1.2-candidate.0';
+
+      processManager = FakeProcessManager.list(<FakeCommand>[
+        const FakeCommand(
+          command: <String>['git', 'fetch', remoteName],
+        ),
+        const FakeCommand(
+          command: <String>[flutterBinPath, 'help'],
+        ),
+        const FakeCommand(
+          command: <String>[flutterBinPath, '--version', '--machine'],
+          stdout: '{"frameworkVersion": "$currentVersion"}',
+        ),
+        FakeCommand(
+          command: const <String>[
+            'git',
+            'branch',
+            '--no-color',
+            '--remotes',
+            '--list',
+            '$remoteName/*',
+          ],
+          stdout: <String>[
+            'other-remote/branch1',
+            '$remoteName/$branch',
+          ].join('\n'),
+        ),
+      ]);
+      final String pathSeparator = operatingSystem == 'windows' ? r'\' : '/';
+
+      platform = FakePlatform(
+        environment: <String, String>{
+          'HOME': <String>['path', 'to', 'home'].join(pathSeparator),
+        },
+        pathSeparator: pathSeparator,
+      );
+      final Checkouts checkouts = Checkouts(
+        fileSystem: fileSystem,
+        parentDirectory: fileSystem.directory(checkoutsParentDirectory),
+        platform: platform,
+        processManager: processManager,
+        stdio: stdio,
+      );
+
+      final CommandRunner<void> runner = createRunner(checkouts: checkouts);
+      await runner.run(<String>['candidates', '--$kRemote', remoteName]);
+      expect(stdio.stdout.contains('currentVersion = $currentVersion'), true);
+      expect(stdio.stdout.contains(branch), true);
+      expect(stdio.stdout.contains('branch1'), false);
+    });
+  }, onPlatform: <String, dynamic>{
+    'windows': const Skip('Flutter Conductor only supported on macos/linux'),
+  });
+}