[flutter_tools] Catch lack of flutter tools source missing (#93168)

packages/flutter_tools/lib/executable.dart

@@ -54,6 +54,7 @@ import 'src/globals.dart' as globals;
 // Files in `isolated` are intentionally excluded from google3 tooling.
 import 'src/isolated/mustache_template.dart';
 import 'src/isolated/resident_web_runner.dart';
+import 'src/pre_run_validator.dart';
 import 'src/resident_runner.dart';
 import 'src/runner/flutter_command.dart';
 import 'src/web/web_runner.dart';
@@ -126,6 +127,7 @@ Future<void> main(List<String> args) async {
           windows: globals.platform.isWindows,
         );
       },
+      PreRunValidator: () => PreRunValidator(fileSystem: globals.fs),
     },
   );
 }

packages/flutter_tools/lib/src/globals.dart

@@ -39,6 +39,7 @@ import 'macos/cocoapods_validator.dart';
 import 'macos/xcdevice.dart';
 import 'macos/xcode.dart';
 import 'persistent_tool_state.dart';
+import 'pre_run_validator.dart';
 import 'project.dart';
 import 'reporting/crash_reporting.dart';
 import 'reporting/reporting.dart';
@@ -257,3 +258,5 @@ FlutterProjectFactory get projectFactory {
 }
 
 CustomDevicesConfig get customDevicesConfig => context.get<CustomDevicesConfig>()!;
+
+PreRunValidator get preRunValidator => context.get<PreRunValidator>() ?? const NoOpPreRunValidator();

packages/flutter_tools/lib/src/pre_run_validator.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 'base/common.dart';
+import 'base/file_system.dart';
+import 'cache.dart';
+
+/// A validator that runs before the tool runs any command.
+abstract class PreRunValidator {
+  factory PreRunValidator({
+    required FileSystem fileSystem,
+  }) => _DefaultPreRunValidator(fileSystem: fileSystem);
+
+  void validate();
+}
+
+class _DefaultPreRunValidator implements PreRunValidator {
+  _DefaultPreRunValidator({
+    required this.fileSystem,
+  });
+
+  final FileSystem fileSystem;
+
+  late final Directory _toolsDir = fileSystem.directory(
+      fileSystem.path.join(Cache.flutterRoot!, 'packages', 'flutter_tools'),
+  );
+
+  @override
+  void validate() {
+    // If a user downloads the Flutter SDK via a pre-built archive and there is
+    // an error during extraction, the user could have a valid Dart snapshot of
+    // the tool but not the source directory. We still need the source, so
+    // validate the source directory exists and toolExit if not.
+    if (!_toolsDir.existsSync()) {
+      throwToolExit(
+        'Flutter SDK installation appears corrupted: expected to find the '
+        'directory ${_toolsDir.path} but it does not exist! Please go to '
+        'https://flutter.dev/setup for instructions on how to re-install '
+        'Flutter.',
+      );
+    }
+  }
+}
+
+class NoOpPreRunValidator implements PreRunValidator {
+  const NoOpPreRunValidator();
+
+  @override
+  void validate() {}
+}

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

@@ -1251,6 +1251,7 @@ abstract class FlutterCommand extends Command<void> {
   /// rather than calling [runCommand] directly.
   @mustCallSuper
   Future<FlutterCommandResult> verifyThenRunCommand(String? commandPath) async {
+    globals.preRunValidator.validate();
     // Populate the cache. We call this before pub get below so that the
     // sky_engine package is available in the flutter cache for pub to find.
     if (shouldUpdateCache) {

packages/flutter_tools/test/commands.shard/hermetic/shell_completion_test.dart

@@ -31,6 +31,8 @@ void main() {
       expect(fakeStdio.writtenToStdout.length, equals(1));
       expect(fakeStdio.writtenToStdout.first, contains('__flutter_completion'));
     }, overrides: <Type, Generator>{
+      FileSystem: () => MemoryFileSystem.test(),
+      ProcessManager: () => FakeProcessManager.any(),
       Stdio: () => fakeStdio,
     });
 
@@ -40,6 +42,8 @@ void main() {
       expect(fakeStdio.writtenToStdout.length, equals(1));
       expect(fakeStdio.writtenToStdout.first, contains('__flutter_completion'));
     }, overrides: <Type, Generator>{
+      FileSystem: () => MemoryFileSystem.test(),
+      ProcessManager: () => FakeProcessManager.any(),
       Stdio: () => fakeStdio,
     });
 

packages/flutter_tools/test/commands.shard/permeable/packages_test.dart

@@ -449,6 +449,7 @@ void main() {
 
     testUsingContext('test without bot', () async {
       Cache.flutterRoot = '';
+      globals.fs.directory('/packages/flutter_tools').createSync(recursive: true);
       globals.fs.file('pubspec.yaml').createSync();
       processManager.addCommand(
         const FakeCommand(command: <String>['/bin/cache/dart-sdk/bin/dart', '__deprecated_pub', 'run', 'test']),

packages/flutter_tools/test/src/common.dart

@@ -162,6 +162,7 @@ void test(String description, FutureOr<void> Function() body, {
       addTearDown(() async {
         await globals.localFileSystem.dispose();
       });
+
       return body();
     },
     skip: skip,