fix issue 12999: Make assets available during tests (flutter#31207)

packages/flutter_test/lib/src/binding.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:typed_data';
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
@@ -16,6 +17,7 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart' show TestWindow;
 import 'package:quiver/testing/async.dart';
 import 'package:quiver/time.dart';
+import 'package:path/path.dart' as path;
 import 'package:test_api/test_api.dart' as test_package;
 import 'package:stack_trace/stack_trace.dart' as stack_trace;
 import 'package:vector_math/vector_math_64.dart';
@@ -707,6 +709,7 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
     super.initInstances();
     window.onBeginFrame = null;
     window.onDrawFrame = null;
+    _mockFlutterAssets();
   }
 
   FakeAsync _currentFakeAsync; // set in runTest; cleared in postTest
@@ -736,6 +739,40 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
   @override
   int get microtaskCount => _currentFakeAsync.microtaskCount;
 
+  static Set<String> _allowedKeys;
+
+  void _mockFlutterAssets() {
+    if (!Platform.environment.containsKey('UNIT_TEST_ASSETS')) {
+      return;
+    }
+    final String assetFolderPath = Platform.environment['UNIT_TEST_ASSETS'];
+    _ensureInitialized(assetFolderPath);
+    BinaryMessages.setMockMessageHandler('flutter/assets', (ByteData message) {
+      final String key = utf8.decode(message.buffer.asUint8List());
+      if (_allowedKeys.contains(key)) {
+        final File asset = File(path.join(assetFolderPath, key));
+        final Uint8List encoded = Uint8List.fromList(asset.readAsBytesSync());
+        return Future<ByteData>.value(encoded.buffer.asByteData());
+      }
+    });
+  }
+
+  void _ensureInitialized(String assetFolderPath) {
+    if (_allowedKeys == null) {
+      final File manifestFile = File(
+          path.join(assetFolderPath, 'AssetManifest.json'));
+      final Map<String, dynamic> manifest = json.decode(
+          manifestFile.readAsStringSync());
+      _allowedKeys = <String>{
+        'AssetManifest.json',
+      };
+      for (List<dynamic> value in manifest.values) {
+        final List<String> strList = List<String>.from(value);
+        _allowedKeys.addAll(strList);
+      }
+    }
+  }
+
   @override
   Future<void> pump([ Duration duration, EnginePhase newPhase = EnginePhase.sendSemanticsUpdate ]) {
     return TestAsyncUtils.guard<void>(() {

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

@@ -5,9 +5,11 @@
 import 'dart:async';
 import 'dart:math' as math;
 
+import '../asset.dart';
 import '../base/common.dart';
 import '../base/file_system.dart';
 import '../base/platform.dart';
+import '../bundle.dart';
 import '../cache.dart';
 import '../codegen.dart';
 import '../dart/pub.dart';
@@ -18,7 +20,6 @@ import '../test/coverage_collector.dart';
 import '../test/event_printer.dart';
 import '../test/runner.dart';
 import '../test/watcher.dart';
-
 class TestCommand extends FastFlutterCommand {
   TestCommand({ bool verboseHelp = false }) {
     requiresPubspecYaml();
@@ -83,7 +84,14 @@ class TestCommand extends FastFlutterCommand {
         abbr: 'j',
         defaultsTo: math.max<int>(1, platform.numberOfProcessors - 2).toString(),
         help: 'The number of concurrent test processes to run.',
-        valueHelp: 'jobs');
+        valueHelp: 'jobs'
+      )
+      ..addFlag('test-assets',
+        defaultsTo: true,
+        negatable: true,
+        help: 'Whether to build the assets bundle for testing.\n'
+              'Consider using --no-test-assets if assets are not required.',
+      );
   }
 
   @override
@@ -110,6 +118,10 @@ class TestCommand extends FastFlutterCommand {
     if (shouldRunPub) {
       await pubGet(context: PubContext.getVerifyContext(name), skipPubspecYamlCheck: true);
     }
+    final bool buildTestAssets = argResults['test-assets'];
+    if (buildTestAssets) {
+      await _buildTestAsset();
+    }
     final List<String> names = argResults['name'];
     final List<String> plainNames = argResults['plain-name'];
     final FlutterProject flutterProject = await FlutterProject.current();
@@ -195,6 +207,7 @@ class TestCommand extends FastFlutterCommand {
       trackWidgetCreation: argResults['track-widget-creation'],
       updateGoldens: argResults['update-goldens'],
       concurrency: jobs,
+      buildTestAssets: buildTestAssets,
       flutterProject: flutterProject,
     );
 
@@ -208,6 +221,15 @@ class TestCommand extends FastFlutterCommand {
       throwToolExit(null);
     return const FlutterCommandResult(ExitStatus.success);
   }
+
+  Future<void> _buildTestAsset() async {
+    final AssetBundle assetBundle = AssetBundleFactory.instance.createBundle();
+    final int build = await assetBundle.build();
+    if (build != 0) {
+      throwToolExit('Error: Failed to build asset bundle');
+    }
+    await writeBundle(fs.directory(fs.path.join('build', 'unit_test_assets')), assetBundle.entries);
+  }
 }
 
 Iterable<String> _findTests(Directory directory) {

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

@@ -88,6 +88,7 @@ void installHook({
   Map<String, String> precompiledDillFiles,
   bool trackWidgetCreation = false,
   bool updateGoldens = false,
+  bool buildTestAssets = false,
   int observatoryPort,
   InternetAddressType serverType = InternetAddressType.IPv4,
   Uri projectRootDirectory,
@@ -110,6 +111,7 @@ void installHook({
       precompiledDillFiles: precompiledDillFiles,
       trackWidgetCreation: trackWidgetCreation,
       updateGoldens: updateGoldens,
+      buildTestAssets: buildTestAssets,
       projectRootDirectory: projectRootDirectory,
       flutterProject: flutterProject,
       icudtlPath: icudtlPath,
@@ -390,6 +392,7 @@ class _FlutterPlatform extends PlatformPlugin {
     this.precompiledDillFiles,
     this.trackWidgetCreation,
     this.updateGoldens,
+    this.buildTestAssets,
     this.projectRootDirectory,
     this.flutterProject,
     this.icudtlPath,
@@ -407,6 +410,7 @@ class _FlutterPlatform extends PlatformPlugin {
   final Map<String, String> precompiledDillFiles;
   final bool trackWidgetCreation;
   final bool updateGoldens;
+  final bool buildTestAssets;
   final Uri projectRootDirectory;
   final FlutterProject flutterProject;
   final String icudtlPath;
@@ -977,6 +981,10 @@ class _FlutterPlatform extends PlatformPlugin {
       'FONTCONFIG_FILE': _fontConfigFile.path,
       'SERVER_PORT': serverPort.toString(),
     };
+    if (buildTestAssets) {
+      environment['UNIT_TEST_ASSETS'] = fs.path.join(
+        flutterProject.directory.path, 'build', 'unit_test_assets');
+    }
     return processManager.start(command, environment: environment);
   }
 

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

@@ -35,6 +35,7 @@ Future<int> runTests(
   bool updateGoldens = false,
   TestWatcher watcher,
   @required int concurrency,
+  bool buildTestAssets = false,
   FlutterProject flutterProject,
   String icudtlPath,
   Directory coverageDirectory,
@@ -83,6 +84,7 @@ Future<int> runTests(
     precompiledDillFiles: precompiledDillFiles,
     trackWidgetCreation: trackWidgetCreation,
     updateGoldens: updateGoldens,
+    buildTestAssets: buildTestAssets,
     projectRootDirectory: fs.currentDirectory.uri,
     flutterProject: flutterProject,
     icudtlPath: icudtlPath,