Support using flutter with specific version (#26840)

* Support using flutter with specific version

* Set min supported version to 1.2.1

packages/flutter_tools/test/commands/version_test.dart

diff --git a/packages/flutter_tools/test/commands/version_test.dart b/packages/flutter_tools/test/commands/version_test.dart
new file mode 100644
index 0000000..aed04a2
--- /dev/null
+++ b/packages/flutter_tools/test/commands/version_test.dart
@@ -0,0 +1,121 @@
+// 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 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter_tools/src/base/io.dart';
+import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/commands/version.dart';
+import 'package:mockito/mockito.dart';
+import 'package:process/process.dart';
+
+import '../src/common.dart';
+import '../src/context.dart';
+import '../src/mocks.dart' show MockProcess;
+
+void main() {
+  group('version', () {
+    setUpAll(() {
+      Cache.disableLocking();
+    });
+
+    testUsingContext('version ls', () async {
+      final VersionCommand command = VersionCommand();
+      await createTestCommandRunner(command).run(<String>['version']);
+      expect(testLogger.statusText, equals('v10.0.0\r\nv20.0.0\n' ''));
+    }, overrides: <Type, Generator>{
+      ProcessManager: () => MockProcessManager(),
+    });
+
+    testUsingContext('version switch', () async {
+      const String version = '10.0.0';
+      final VersionCommand command = VersionCommand();
+      final Future<void> runCommand = createTestCommandRunner(command).run(<String>['version', version]);
+      await Future.wait<void>(<Future<void>>[runCommand]);
+      expect(testLogger.statusText, contains('Switching Flutter to version $version'));
+    }, overrides: <Type, Generator>{
+      ProcessManager: () => MockProcessManager(),
+    });
+
+    testUsingContext('switch to not supported version without force', () async {
+      const String version = '1.1.5';
+      final VersionCommand command = VersionCommand();
+      final Future<void> runCommand = createTestCommandRunner(command).run(<String>['version', version]);
+      await Future.wait<void>(<Future<void>>[runCommand]);
+      expect(testLogger.errorText, contains('Version command is not supported in'));
+    }, overrides: <Type, Generator>{
+      ProcessManager: () => MockProcessManager(),
+    });
+
+    testUsingContext('switch to not supported version with force', () async {
+      const String version = '1.1.5';
+      final VersionCommand command = VersionCommand();
+      final Future<void> runCommand = createTestCommandRunner(command).run(<String>['version', '--force', version]);
+      await Future.wait<void>(<Future<void>>[runCommand]);
+      expect(testLogger.statusText, contains('Switching Flutter to version $version with force'));
+    }, overrides: <Type, Generator>{
+      ProcessManager: () => MockProcessManager(),
+    });
+  });
+}
+
+class MockProcessManager extends Mock implements ProcessManager {
+  String version = '';
+
+  @override
+  Future<ProcessResult> run(
+    List<dynamic> command, {
+    String workingDirectory,
+    Map<String, String> environment,
+    bool includeParentEnvironment = true,
+    bool runInShell = false,
+    Encoding stdoutEncoding = systemEncoding,
+    Encoding stderrEncoding = systemEncoding,
+  }) async {
+    if (command[0] == 'git' && command[1] == 'tag') {
+      return ProcessResult(0, 0, 'v10.0.0\r\nv20.0.0', '');
+    }
+    if (command[0] == 'git' && command[1] == 'checkout') {
+      version = command[2];
+    }
+    return ProcessResult(0, 0, '', '');
+  }
+
+  @override
+  ProcessResult runSync(
+    List<dynamic> command, {
+    String workingDirectory,
+    Map<String, String> environment,
+    bool includeParentEnvironment = true,
+    bool runInShell = false,
+    Encoding stdoutEncoding = systemEncoding,
+    Encoding stderrEncoding = systemEncoding,
+  }) {
+    final String commandStr = command.join(' ');
+    if (commandStr == 'git log -n 1 --pretty=format:%H') {
+      return ProcessResult(0, 0, '000000000000000000000', '');
+    }
+    if (commandStr ==
+        'git describe --match v*.*.* --first-parent --long --tags') {
+      if (version.isNotEmpty) {
+        return ProcessResult(0, 0, '$version-0-g00000000', '');
+      }
+    }
+    return ProcessResult(0, 0, '', '');
+  }
+
+  @override
+  Future<Process> start(List<dynamic> command,
+      {String workingDirectory,
+      Map<String, String> environment,
+      bool includeParentEnvironment = true,
+      bool runInShell = false,
+      ProcessStartMode mode = ProcessStartMode.normal}) {
+    final Completer<Process> completer = Completer<Process>();
+    completer.complete(MockProcess());
+    return completer.future;
+  }
+}