Write the package config location to the test bootstrap. (#150440)

Work towards. This is the Flutter companion to
https://github.com/dart-lang/test/pull/2245. Work towards
https://github.com/dart-lang/test/issues/2246.

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

@@ -618,6 +618,7 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
         integrationTestUserIdentifier: stringArg(FlutterOptions.kDeviceUser),
         testTimeRecorder: testTimeRecorder,
         nativeAssetsBuilder: nativeAssetsBuilder,
+        buildInfo: buildInfo,
       );
     }
     testTimeRecorder?.stop(TestTimePhases.TestRunner, testRunnerTimeRecorderStopwatch!);

packages/flutter_tools/lib/src/test/flutter_platform.dart

@@ -15,6 +15,7 @@ import 'package:test_core/src/platform.dart'; // ignore: implementation_imports
 import '../base/common.dart';
 import '../base/file_system.dart';
 import '../base/io.dart';
+import '../build_info.dart';
 import '../cache.dart';
 import '../compile.dart';
 import '../convert.dart';
@@ -71,6 +72,7 @@ FlutterPlatform installHook({
   TestTimeRecorder? testTimeRecorder,
   UriConverter? uriConverter,
   TestCompilerNativeAssetsBuilder? nativeAssetsBuilder,
+  BuildInfo? buildInfo,
 }) {
   assert(enableVmService || enableObservatory || (!debuggingOptions.startPaused && debuggingOptions.hostVmServicePort == null));
 
@@ -102,6 +104,7 @@ FlutterPlatform installHook({
     testTimeRecorder: testTimeRecorder,
     uriConverter: uriConverter,
     nativeAssetsBuilder: nativeAssetsBuilder,
+    buildInfo: buildInfo,
   );
   platformPluginRegistration(platform);
   return platform;
@@ -120,6 +123,9 @@ FlutterPlatform installHook({
 /// configuration files as outlined in the [flutter_test] library. By default,
 /// the test file will be launched directly.
 ///
+/// The [packageConfigUri] argument specifies the package config location for
+/// the test file being launched. This is expected to be a file URI.
+///
 /// The [updateGoldens] argument will set the [autoUpdateGoldens] global
 /// variable in the [flutter_test] package before invoking the test.
 ///
@@ -132,6 +138,7 @@ String generateTestBootstrap({
   required Uri testUrl,
   required InternetAddress host,
   File? testConfigFile,
+  Uri? packageConfigUri,
   bool updateGoldens = false,
   String languageVersionHeader = '',
   bool nullSafety = false,
@@ -174,6 +181,15 @@ import '$testUrl' as test;
 import '${Uri.file(testConfigFile.path)}' as test_config;
 ''');
   }
+
+  // IMPORTANT: DO NOT RENAME, REMOVE, OR MODIFY THE
+  // 'const packageConfigLocation' VARIABLE.
+  // Dash tooling like Dart DevTools performs an evaluation on this variable at
+  // runtime to get the package config location for Flutter test targets.
+  buffer.write('''
+
+const packageConfigLocation = '$packageConfigUri';
+''');
   buffer.write('''
 
 /// Returns a serialized test suite.
@@ -295,6 +311,7 @@ class FlutterPlatform extends PlatformPlugin {
     this.testTimeRecorder,
     this.uriConverter,
     this.nativeAssetsBuilder,
+    this.buildInfo,
   });
 
   final String shellPath;
@@ -312,6 +329,7 @@ class FlutterPlatform extends PlatformPlugin {
   final String? icudtlPath;
   final TestTimeRecorder? testTimeRecorder;
   final TestCompilerNativeAssetsBuilder? nativeAssetsBuilder;
+  final BuildInfo? buildInfo;
 
   // This can be used by internal projects that require custom logic for converting package: URIs to local paths.
   final UriConverter? uriConverter;
@@ -641,6 +659,8 @@ class FlutterPlatform extends PlatformPlugin {
     return generateTestBootstrap(
       testUrl: testUrl,
       testConfigFile: findTestConfigFile(globals.fs.file(testUrl), globals.logger),
+      // This MUST be a file URI.
+      packageConfigUri: buildInfo != null ? globals.fs.path.toUri(buildInfo!.packageConfigPath) : null,
       host: host!,
       updateGoldens: updateGoldens!,
       flutterTestDep: packageConfig['flutter_test'] != null,

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

@@ -64,6 +64,7 @@ abstract class FlutterTestRunner {
     String? integrationTestUserIdentifier,
     TestTimeRecorder? testTimeRecorder,
     TestCompilerNativeAssetsBuilder? nativeAssetsBuilder,
+    BuildInfo? buildInfo,
   });
 
   /// Runs tests using the experimental strategy of spawning each test in a
@@ -131,6 +132,7 @@ class _FlutterTestRunnerImpl implements FlutterTestRunner {
     String? integrationTestUserIdentifier,
     TestTimeRecorder? testTimeRecorder,
     TestCompilerNativeAssetsBuilder? nativeAssetsBuilder,
+    BuildInfo? buildInfo,
   }) async {
     // Configure package:test to use the Flutter engine for child processes.
     final String shellPath = globals.artifacts!.getArtifactPath(Artifact.flutterTester);
@@ -258,6 +260,7 @@ class _FlutterTestRunnerImpl implements FlutterTestRunner {
       integrationTestUserIdentifier: integrationTestUserIdentifier,
       testTimeRecorder: testTimeRecorder,
       nativeAssetsBuilder: nativeAssetsBuilder,
+      buildInfo: buildInfo,
     );
 
     try {

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

@@ -13,6 +13,7 @@ import 'package:flutter_tools/src/base/common.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/terminal.dart';
+import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/commands/test.dart';
 import 'package:flutter_tools/src/device.dart';
@@ -1479,6 +1480,7 @@ class FakeFlutterTestRunner implements FlutterTestRunner {
     String? integrationTestUserIdentifier,
     TestTimeRecorder? testTimeRecorder,
     TestCompilerNativeAssetsBuilder? nativeAssetsBuilder,
+    BuildInfo? buildInfo,
   }) async {
     lastEnableVmServiceValue = enableVmService;
     lastDebuggingOptionsValue = debuggingOptions;

packages/flutter_tools/test/general.shard/flutter_platform_test.dart

@@ -122,4 +122,41 @@ void main() {
       expect(flutterPlatform.uriConverter?.call('hello'), 'hello/test');
     });
   });
+
+  group('generateTestBootstrap', () {
+    group('writes a "const packageConfigLocation" string', () {
+      test('with null packageConfigUri', () {
+        final String contents = generateTestBootstrap(
+          testUrl:
+              Uri.parse('file:///Users/me/some_package/test/some_test.dart'),
+          host: InternetAddress('127.0.0.1', type: InternetAddressType.IPv4),
+        );
+        // IMPORTANT: DO NOT RENAME, REMOVE, OR MODIFY THE
+        // 'const packageConfigLocation' VARIABLE.
+        // Dash tooling like Dart DevTools performs an evaluation on this variable
+        // at runtime to get the package config location for Flutter test targets.
+        expect(contents, contains("const packageConfigLocation = 'null';"));
+      });
+
+      test('with non-null packageConfigUri', () {
+        final String contents = generateTestBootstrap(
+          testUrl:
+              Uri.parse('file:///Users/me/some_package/test/some_test.dart'),
+          host: InternetAddress('127.0.0.1', type: InternetAddressType.IPv4),
+          packageConfigUri: Uri.parse(
+              'file:///Users/me/some_package/.dart_tool/package_config.json'),
+        );
+        // IMPORTANT: DO NOT RENAME, REMOVE, OR MODIFY THE
+        // 'const packageConfigLocation' VARIABLE.
+        // Dash tooling like Dart DevTools performs an evaluation on this variable
+        // at runtime to get the package config location for Flutter test targets.
+        expect(
+          contents,
+          contains(
+            "const packageConfigLocation = 'file:///Users/me/some_package/.dart_tool/package_config.json';",
+          ),
+        );
+      });
+    });
+  });
 }