Add error logging to flutter generate (#42209)

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

@@ -2,9 +2,11 @@
 // 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';
 import '../codegen.dart';
+import '../convert.dart';
+import '../globals.dart';
 import '../project.dart';
 import '../runner/flutter_command.dart';
 
@@ -18,9 +20,6 @@ class GenerateCommand extends FlutterCommand {
   @override
   String get name => 'generate';
 
-  @override
-  bool get hidden => true;
-
   @override
   Future<Set<DevelopmentArtifact>> get requiredArtifacts async => const <DevelopmentArtifact>{
     DevelopmentArtifact.universal,
@@ -34,12 +33,34 @@ class GenerateCommand extends FlutterCommand {
     codegenDaemon.startBuild();
     await for (CodegenStatus codegenStatus in codegenDaemon.buildResults) {
       if (codegenStatus == CodegenStatus.Failed) {
-        throwToolExit('Code generation failed');
+        printError('Code generation failed.');
+        break;
       }
       if (codegenStatus ==CodegenStatus.Succeeded) {
         break;
       }
     }
-    return null;
+    // Check for errors output in the build_runner cache.
+    final Directory buildDirectory = flutterProject.dartTool.childDirectory('build');
+    final Directory errorCacheParent = buildDirectory.listSync().firstWhere((FileSystemEntity entity) {
+      return entity is Directory && entity.childDirectory('error_cache').existsSync();
+    }, orElse: () => null);
+    if (errorCacheParent == null) {
+      return null;
+    }
+    final Directory errorCache = errorCacheParent.childDirectory('error_cache');
+    for (File errorFile in errorCache.listSync(recursive: true).whereType<File>()) {
+      try {
+        final List<Object> errorData = json.decode(errorFile.readAsStringSync());
+        final List<Object> stackData = errorData[1];
+        printError(errorData.first);
+        printError(stackData[0]);
+        printError(stackData[1]);
+        printError(StackTrace.fromString(stackData[2]).toString());
+      } catch (err) {
+        printError('Error reading error in ${errorFile.path}');
+      }
+    }
+    return const FlutterCommandResult(ExitStatus.fail);
   }
 }

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

@@ -0,0 +1,82 @@
+// 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 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/codegen.dart';
+import 'package:flutter_tools/src/commands/generate.dart';
+import 'package:flutter_tools/src/convert.dart';
+import 'package:flutter_tools/src/globals.dart';
+import 'package:mockito/mockito.dart';
+
+import '../../src/common.dart';
+import '../../src/mocks.dart';
+import '../../src/testbed.dart';
+
+void main() {
+  Testbed testbed;
+  MockCodeGenerator mockCodeGenerator;
+  MockCodegenDaemon mockCodegenDaemon;
+
+  setUpAll(() {
+    Cache.disableLocking();
+  });
+
+  tearDownAll(() {
+    Cache.enableLocking();
+  });
+
+  setUp(() {
+    mockCodegenDaemon = MockCodegenDaemon();
+    mockCodeGenerator = MockCodeGenerator();
+    when(mockCodegenDaemon.buildResults).thenAnswer((Invocation invocation) {
+      return Stream<CodegenStatus>.fromIterable(<CodegenStatus>[
+        CodegenStatus.Started,
+        CodegenStatus.Succeeded,
+      ]);
+    });
+    when(mockCodeGenerator.daemon(any)).thenAnswer((Invocation invocation) async {
+      return mockCodegenDaemon;
+    });
+    testbed = Testbed(overrides: <Type, Generator>{
+      CodeGenerator: () => mockCodeGenerator,
+    });
+  });
+
+  test('Outputs error information from flutter generate', () => testbed.run(() async {
+    final GenerateCommand command = GenerateCommand();
+    final BufferLogger bufferLogger = logger;
+    applyMocksToCommand(command);
+    fs.file(fs.path.join('lib', 'main.dart'))
+      ..createSync(recursive: true);
+
+    fs.currentDirectory
+      .childDirectory('.dart_tool')
+      .childDirectory('build')
+      .childDirectory('abcdefg')
+      .childDirectory('error_cache')
+      .childFile('foo_error')
+      ..createSync(recursive: true)
+      ..writeAsStringSync(json.encode(<dynamic>[
+        'foo builder',
+        <dynamic>[
+          'a',
+          'b',
+          StackTrace.current.toString(),
+        ]
+      ]));
+
+    await createTestCommandRunner(command)
+      .run(const <String>['generate']);
+
+    expect(bufferLogger.errorText, contains('a'));
+    expect(bufferLogger.errorText, contains('b'));
+    expect(bufferLogger.errorText, contains('foo builder'));
+    expect(bufferLogger.errorText, isNot(contains('Error reading error')));
+  }));
+}
+
+class MockCodeGenerator extends Mock implements CodeGenerator { }
+class MockCodegenDaemon extends Mock implements CodegenDaemon { }