Lookup the package config location for Dart and Flutter test targets

packages/devtools_app_shared/lib/src/service/service_manager.dart

@@ -16,6 +16,7 @@ import 'package:vm_service/vm_service.dart' hide Error;
 import '../utils/utils.dart';
 import 'connected_app.dart';
 import 'dtd_manager.dart';
+import 'eval_on_dart_library.dart' hide SentinelException;
 import 'flutter_version.dart';
 import 'isolate_manager.dart';
 import 'isolate_state.dart';
@@ -521,32 +522,74 @@ class ServiceManager<T extends VmService> {
     // VM service connection spawned from `dart test` or `flutter test`).
     if (packageRootUriString?.endsWith('.dart') ?? false) {
       final rootLibrary = await _mainIsolateRootLibrary();
-      final testTargetFileUriString =
-          (rootLibrary?.dependencies ?? <LibraryDependency>[])
-              .firstWhereOrNull((dep) => dep.prefix == 'test')
-              ?.target
-              ?.uri;
-      if (testTargetFileUriString != null) {
-        _log.fine(
-          '[connectedAppPackageRoot] detected test library from root library '
-          'imports: $testTargetFileUriString',
-        );
-        packageRootUriString = await packageRootFromFileUriString(
-          testTargetFileUriString,
-          dtd: dtdManager.connection.value,
-        );
-        _log.fine(
-          '[connectedAppPackageRoot] package root for test target: '
-          '$packageRootUriString',
-        );
+      if (rootLibrary != null) {
+        packageRootUriString =
+            (await _lookupPackageConfigByEval(rootLibrary)) ??
+                // TODO(kenz): remove this fallback once all test bootstrap
+                // generators include the `packageConfigLocation` constant we
+                // can evaluate.
+                await _lookupTestLibraryByPrefix(rootLibrary, dtdManager);
       }
     }
-
+    _log.fine(
+      '[connectedAppPackageRoot] package root for test target: '
+      '$packageRootUriString',
+    );
     return packageRootUriString == null
         ? null
         : Uri.parse(packageRootUriString);
   }
 
+  Future<String?> _lookupPackageConfigByEval(Library rootLibrary) async {
+    final eval = EvalOnDartLibrary(
+      rootLibrary.uri!,
+      this.service! as VmService,
+      serviceManager: this,
+    );
+    final evalDisposable = Disposable();
+    final packageConfig = (await eval.evalInstance(
+      'packageConfigLocation',
+      isAlive: evalDisposable,
+    ))
+        .valueAsString;
+    evalDisposable.dispose();
+
+    if (packageConfig?.endsWith(packageConfigIdentifier) ?? false) {
+      _log.fine(
+        '[connectedAppPackageRoot] detected test package config from root '
+        'library eval: $packageConfig.',
+      );
+      return packageConfig!.substring(
+        0,
+        // Minus 1 to remove the trailing slash.
+        packageConfig.length - packageConfigIdentifier.length - 1,
+      );
+    }
+    return null;
+  }
+
+  Future<String?> _lookupTestLibraryByPrefix(
+    Library rootLibrary,
+    DTDManager dtdManager,
+  ) async {
+    final testTargetFileUriString =
+        (rootLibrary.dependencies ?? <LibraryDependency>[])
+            .firstWhereOrNull((dep) => dep.prefix == 'test')
+            ?.target
+            ?.uri;
+    if (testTargetFileUriString != null) {
+      _log.fine(
+        '[connectedAppPackageRoot] detected test library from root library '
+        'imports: $testTargetFileUriString',
+      );
+      return await packageRootFromFileUriString(
+        testTargetFileUriString,
+        dtd: dtdManager.connection.value,
+      );
+    }
+    return null;
+  }
+
   Future<Library?> _mainIsolateRootLibrary() async {
     final ref =
         (await isolateManager.waitForMainIsolateState())?.isolateNow?.rootLib;

packages/devtools_shared/lib/src/common.dart

@@ -2,5 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:path/path.dart' as path;
+
 /// Describes an instance of the Dart Tooling Daemon.
 typedef DTDConnectionInfo = ({String? uri, String? secret});
+
+/// The name of the Directory where a Dart application's package config file is
+/// stored.
+const dartToolDirectoryName = '.dart_tool';
+
+/// The name of the package config file for a Dart application.
+const packageConfigFileName = 'package_config.json';
+
+/// The path identifier for the package config URI for a Dart application.
+///
+/// The package config file lives at '.dart_tool/package_config.json'.
+final packageConfigIdentifier =
+    path.join(dartToolDirectoryName, packageConfigFileName);

packages/devtools_shared/lib/src/extensions/extension_manager.dart

@@ -146,8 +146,8 @@ class ExtensionsManager {
       // may be an incorrect assumption for monorepos.
       final packageConfigPath = path.posix.join(
         rootFileUriString,
-        '.dart_tool',
-        'package_config.json',
+        dartToolDirectoryName,
+        packageConfigFileName,
       );
       extensions = await findExtensions(
         'devtools',

packages/devtools_shared/lib/src/utils/file_utils.dart

@@ -5,6 +5,8 @@
 import 'package:dtd/dtd.dart';
 import 'package:meta/meta.dart';
 
+import '../common.dart';
+
 const _fileUriPrefix = 'file://';
 
 /// Attempts to detect the package root of [fileUriString], which is expected to
@@ -52,7 +54,7 @@ Future<String> packageRootFromFileUriString(
       try {
         final directoryContents = await dtd.listDirectoryContents(uri);
         final containsDartToolDirectory = (directoryContents.uris ?? const [])
-            .any((uri) => uri.path.endsWith('.dart_tool/'));
+            .any((uri) => uri.path.endsWith('$dartToolDirectoryName/'));
         if (containsDartToolDirectory) {
           final uriAsString = uri.toString();
           return _assertUriFormatAndReturn(

packages/devtools_shared/test/helpers/extension_test_manager.dart

@@ -4,6 +4,7 @@
 
 import 'dart:io';
 
+import 'package:devtools_shared/devtools_shared.dart';
 import 'package:path/path.dart' as p;
 import 'package:test/test.dart';
 
@@ -109,10 +110,7 @@ class ExtensionTestManager {
         );
       }
 
-      final packageConfigFile = File(
-        p.join(packageRoot.path, '.dart_tool', 'package_config.json'),
-      );
-      expect(packageConfigFile.existsSync(), isTrue);
+      expect(File(packageConfigIdentifier).existsSync(), isTrue);
     }
   }