Update upgrade to reset off of hotfix branches (#29786)

packages/flutter_tools/lib/src/commands/upgrade.dart

@@ -18,6 +18,15 @@ import '../version.dart';
 import 'channel.dart';
 
 class UpgradeCommand extends FlutterCommand {
+  UpgradeCommand() {
+    argParser.addFlag(
+      'force',
+      abbr: 'f',
+      help: 'force upgrade the flutter branch, potentially discarding local changes.',
+      negatable: false,
+    );
+  }
+
   @override
   final String name = 'upgrade';
 
@@ -29,64 +38,146 @@ class UpgradeCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
+    final UpgradeCommandRunner upgradeCommandRunner = UpgradeCommandRunner();
+    await upgradeCommandRunner.runCommand(argResults['force'], GitTagVersion.determine(), FlutterVersion.instance);
+    return null;
+  }
+}
+
+
+@visibleForTesting
+class UpgradeCommandRunner {
+  Future<FlutterCommandResult> runCommand(bool force, GitTagVersion gitTagVersion, FlutterVersion flutterVersion) async {
+    await verifyUpstreamConfigured();
+    if (!force && gitTagVersion == const GitTagVersion.unknown()) {
+      // If the commit is a recognized branch and not master,
+      // explain that we are avoiding potential damage.
+      if (flutterVersion.channel != 'master' && FlutterVersion.officialChannels.contains(flutterVersion.channel)) {
+        throwToolExit(
+          'Unknown flutter tag. Abandoning upgrade to avoid destroying local '
+          'changes. It is recommended to use git directly if not working on '
+          'an official channel.'
+        );
+      // Otherwise explain that local changes can be lost.
+      } else {
+        throwToolExit(
+          'Unknown flutter tag. Abandoning upgrade to avoid destroying local '
+          'changes. If it is okay to remove local changes, then re-run this '
+          'command with --force.'
+        );
+      }
+    }
+    await resetChanges(gitTagVersion);
+    await upgradeChannel(flutterVersion);
+    await attemptFastForward();
+    await precacheArtifacts();
+    await updatePackages(flutterVersion);
+    await runDoctor();
+    return null;
+  }
+
+  /// Check if there is an upstream repository configured.
+  ///
+  /// Exits tool if there is no upstream.
+  Future<void> verifyUpstreamConfigured() async {
     try {
       await runCheckedAsync(<String>[
         'git', 'rev-parse', '@{u}',
       ], workingDirectory: Cache.flutterRoot);
     } catch (e) {
-      throwToolExit('Unable to upgrade Flutter: no upstream repository configured.');
+      throwToolExit(
+        'Unable to upgrade Flutter: no origin repository configured. '
+        'Run \'git remote add origin '
+        'https://github.com/flutter/flutter\' in ${Cache.flutterRoot}',
+      );
     }
+  }
 
-    final FlutterVersion flutterVersion = FlutterVersion.instance;
+  /// Attempts to reset to the last known tag or branch. This should restore the
+  /// history to something that is compatible with the regular upgrade
+  /// process.
+  Future<void> resetChanges(GitTagVersion gitTagVersion) async {
+    // We only got here by using --force.
+    String tag;
+    if (gitTagVersion == const GitTagVersion.unknown()) {
+      tag = 'v0.0.0';
+    } else {
+      tag = 'v${gitTagVersion.x}.${gitTagVersion.y}.${gitTagVersion.z}';
+    }
+    final RunResult runResult = await runCheckedAsync(<String>[
+      'git', 'reset', '--hard', tag,
+    ], workingDirectory: Cache.flutterRoot);
+    if (runResult.exitCode != 0) {
+      throwToolExit('Failed to restore branch from hotfix.');
+    }
+  }
 
+  /// Attempts to upgrade the channel.
+  ///
+  /// If the user is on a deprecated channel, attempts to migrate them off of
+  /// it.
+  Future<void> upgradeChannel(FlutterVersion flutterVersion) async {
     printStatus('Upgrading Flutter from ${Cache.flutterRoot}...');
-
     await ChannelCommand.upgradeChannel();
+  }
 
-    int code = await runCommandAndStreamOutput(
-      <String>['git', 'pull', '--ff-only'],
+  /// Attempts to rebase the upstream onto the local branch.
+  ///
+  /// If there haven't been any hot fixes or local changes, this is equivalent
+  /// to a fast-forward.
+  Future<void> attemptFastForward() async {
+    final int code = await runCommandAndStreamOutput(
+      <String>['git', 'pull', '--ff'],
       workingDirectory: Cache.flutterRoot,
       mapFunction: (String line) => matchesGitLine(line) ? null : line,
     );
-
-    if (code != 0)
+    if (code != 0) {
       throwToolExit(null, exitCode: code);
+    }
+  }
 
-    // Check for and download any engine and pkg/ updates.
-    // We run the 'flutter' shell script re-entrantly here
-    // so that it will download the updated Dart and so forth
-    // if necessary.
+  /// Update the engine repository and precache all artifacts.
+  ///
+  /// Check for and download any engine and pkg/ updates. We run the 'flutter'
+  /// shell script re-entrantly here so that it will download the updated
+  /// Dart and so forth if necessary.
+  Future<void> precacheArtifacts() async {
     printStatus('');
     printStatus('Upgrading engine...');
-    code = await runCommandAndStreamOutput(
+    final int code = await runCommandAndStreamOutput(
       <String>[
         fs.path.join('bin', 'flutter'), '--no-color', '--no-version-check', 'precache',
       ],
       workingDirectory: Cache.flutterRoot,
       allowReentrantFlutter: true,
     );
+    if (code != 0) {
+      throwToolExit(null, exitCode: code);
+    }
+  }
 
+  /// Update the user's packages.
+  Future<void> updatePackages(FlutterVersion flutterVersion) async {
     printStatus('');
     printStatus(flutterVersion.toString());
-
     final String projectRoot = findProjectRoot();
     if (projectRoot != null) {
       printStatus('');
       await pubGet(context: PubContext.pubUpgrade, directory: projectRoot, upgrade: true, checkLastModified: false);
     }
+  }
 
-    // Run a doctor check in case system requirements have changed.
+  /// Run flutter doctor in case requirements have changed.
+  Future<void> runDoctor() async {
     printStatus('');
     printStatus('Running flutter doctor...');
-    code = await runCommandAndStreamOutput(
+    await runCommandAndStreamOutput(
       <String>[
         fs.path.join('bin', 'flutter'), '--no-version-check', 'doctor',
       ],
       workingDirectory: Cache.flutterRoot,
       allowReentrantFlutter: true,
     );
-
-    return null;
   }
 
   //  dev/benchmarks/complex_layout/lib/main.dart        |  24 +-
@@ -97,7 +188,6 @@ class UpgradeCommand extends FlutterCommand {
   //  create mode 100644 examples/flutter_gallery/lib/gallery/demo.dart
   static final RegExp _gitChangedRegex = RegExp(r' (rename|delete mode|create mode) .+');
 
-  @visibleForTesting
   static bool matchesGitLine(String line) {
     return _gitDiffRegex.hasMatch(line)
       || _gitChangedRegex.hasMatch(line)

packages/flutter_tools/test/commands/upgrade_test.dart

@@ -2,21 +2,83 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter_tools/src/base/common.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/os.dart';
 import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/commands/upgrade.dart';
+import 'package:flutter_tools/src/runner/flutter_command.dart';
+import 'package:flutter_tools/src/version.dart';
+import 'package:mockito/mockito.dart';
+import 'package:process/process.dart';
 
 import '../src/common.dart';
 import '../src/context.dart';
 
 void main() {
-  group('upgrade', () {
+  group('UpgradeCommandRunner', () {
+    FakeUpgradeCommandRunner fakeCommandRunner;
+    UpgradeCommandRunner realCommandRunner;
+    MockProcessManager processManager;
+    final MockFlutterVersion flutterVersion = MockFlutterVersion();
+    const GitTagVersion gitTagVersion = GitTagVersion(1, 2, 3, 4, 5, 'asd');
+    when(flutterVersion.channel).thenReturn('dev');
+
+    setUp(() {
+      fakeCommandRunner = FakeUpgradeCommandRunner();
+      realCommandRunner = UpgradeCommandRunner();
+      processManager = MockProcessManager();
+    });
+
+    test('throws on unknown tag, official branch,  noforce', () async {
+      final Future<FlutterCommandResult> result = fakeCommandRunner.runCommand(
+        false,
+        const GitTagVersion.unknown(),
+        flutterVersion,
+      );
+      expect(result, throwsA(isInstanceOf<ToolExit>()));
+    });
+
+    test('does not throw on unknown tag, official branch, force', () async {
+      final Future<FlutterCommandResult> result = fakeCommandRunner.runCommand(
+        true,
+        const GitTagVersion.unknown(),
+        flutterVersion,
+      );
+      expect(await result, null);
+    });
+
+    test('Doesn\'t throw on known tag, dev branch, no force', () async {
+      final Future<FlutterCommandResult> result = fakeCommandRunner.runCommand(
+        false,
+        gitTagVersion,
+        flutterVersion,
+      );
+      expect(await result, null);
+    });
+
+    testUsingContext('verifyUpstreamConfigured', () async {
+      when(processManager.run(
+        <String>['git', 'rev-parse', '@{u}'],
+        environment:anyNamed('environment'),
+        workingDirectory: anyNamed('workingDirectory'))
+      ).thenAnswer((Invocation invocation) async {
+        return FakeProcessResult()
+          ..exitCode = 0;
+      });
+      await realCommandRunner.verifyUpstreamConfigured();
+    }, overrides: <Type, Generator>{
+      ProcessManager: () => processManager,
+    });
+  });
+
+  group('matchesGitLine', () {
     setUpAll(() {
       Cache.disableLocking();
     });
 
-    bool _match(String line) => UpgradeCommand.matchesGitLine(line);
+    bool _match(String line) => UpgradeCommandRunner.matchesGitLine(line);
 
     test('regex match', () {
       expect(_match(' .../flutter_gallery/lib/demo/buttons_demo.dart    | 10 +--'), true);
@@ -63,3 +125,42 @@ void main() {
     });
   });
 }
+
+class FakeUpgradeCommandRunner extends UpgradeCommandRunner {
+  @override
+  Future<void> verifyUpstreamConfigured() async {}
+
+  @override
+  Future<void> resetChanges(GitTagVersion gitTagVersion) async {}
+
+  @override
+  Future<void> upgradeChannel(FlutterVersion flutterVersion) async {}
+
+  @override
+  Future<void> attemptFastForward() async {}
+
+  @override
+  Future<void> precacheArtifacts() async {}
+
+  @override
+  Future<void> updatePackages(FlutterVersion flutterVersion) async {}
+
+  @override
+  Future<void> runDoctor() async {}
+}
+
+class MockFlutterVersion extends Mock implements FlutterVersion {}
+class MockProcessManager extends Mock implements ProcessManager {}
+class FakeProcessResult implements ProcessResult {
+  @override
+  int exitCode;
+
+  @override
+  int pid = 0;
+
+  @override
+  String stderr = '';
+
+  @override
+  String stdout = '';
+}