delete golden files; switch to flutter/goldens (#12434)

Delete golden files from flutter/engine; switch to flutter/goldens

lib/web_ui/dev/README.md

@@ -20,3 +20,15 @@ or:
 ```
 felt build --watch
 ```
+
+## Configuration files
+
+`chrome_lock.yaml` contains the version of Chrome we use to test Flutter for
+web. Chrome is not automatically updated whenever a new release is available.
+Instead, we update this file manually once in a while.
+
+`goldens_lock.yaml` refers to a revision in the https://github.com/flutter/goldens
+repo. Screenshot tests are compared with the golden files at that revision.
+When making engine changes that affect screenshots, first submit a PR to
+flutter/goldens updating the screenshots. Then update this file pointing to
+the new revision.

lib/web_ui/dev/environment.dart

@@ -103,4 +103,17 @@ class Environment {
     webUiRootDir.path,
     '.dart_tool',
   ));
+
+  /// Path to the "dev" directory containing engine developer tools and
+  /// configuration files.
+  io.Directory get webUiDevDir => io.Directory(pathlib.join(
+    webUiRootDir.path,
+    'dev',
+  ));
+
+  /// Path to the clone of the flutter/goldens repository.
+  io.Directory get webUiGoldensRepositoryDirectory => io.Directory(pathlib.join(
+    webUiDartToolDir.path,
+    'goldens',
+  ));
 }

lib/web_ui/dev/goldens.dart

@@ -3,6 +3,11 @@
 // found in the LICENSE file.
 import 'dart:io' as io;
 import 'package:image/image.dart';
+import 'package:path/path.dart' as path;
+import 'package:yaml/yaml.dart';
+
+import 'environment.dart';
+import 'utils.dart';
 
 void main(List<String> args) {
   final io.File fileA = io.File(args[0]);
@@ -10,7 +15,7 @@ void main(List<String> args) {
   final Image imageA = decodeNamedImage(fileA.readAsBytesSync(), 'a.png');
   final Image imageB = decodeNamedImage(fileB.readAsBytesSync(), 'b.png');
   final ImageDiff diff = ImageDiff(golden: imageA, other: imageB);
-  print('Diff: ${(diff.rate * 100).toStringAsFixed(4)}');
+  print('Diff: ${(diff.rate * 100).toStringAsFixed(4)}%');
 }
 
 /// This class encapsulates visually diffing an Image with any other.
@@ -140,3 +145,72 @@ class ImageDiff {
 String getPrintableDiffFilesInfo(double diffRate, double maxRate) =>
   '(${((diffRate) * 100).toStringAsFixed(4)}% of pixels were different. '
   'Maximum allowed rate is: ${(maxRate * 100).toStringAsFixed(4)}%).';
+
+/// Fetches golden files from github.com/flutter/goldens, cloning the repository if necessary.
+///
+/// The repository is cloned into web_ui/.dart_tool.
+Future<void> fetchGoldens() async {
+  await _GoldensRepoFetcher().fetch();
+}
+
+class _GoldensRepoFetcher {
+  String _repository;
+  String _revision;
+
+  Future<void> fetch() async {
+    final io.File lockFile = io.File(
+      path.join(environment.webUiDevDir.path, 'goldens_lock.yaml')
+    );
+    final YamlMap lock = loadYaml(lockFile.readAsStringSync());
+    _repository = lock['repository'];
+    _revision = lock['revision'];
+
+    final String localRevision = await _getLocalRevision();
+    if (localRevision == _revision) {
+      return;
+    }
+
+    print('Fetching $_repository@$_revision');
+
+    if (!environment.webUiGoldensRepositoryDirectory.existsSync()) {
+      environment.webUiGoldensRepositoryDirectory.createSync(recursive: true);
+      await runProcess(
+        'git',
+        <String>['init'],
+        workingDirectory: environment.webUiGoldensRepositoryDirectory.path,
+        mustSucceed: true,
+      );
+      await runProcess(
+        'git',
+        <String>['remote', 'add', 'origin', _repository],
+        workingDirectory: environment.webUiGoldensRepositoryDirectory.path,
+        mustSucceed: true,
+      );
+    }
+
+    await runProcess(
+      'git',
+      <String>['fetch', 'origin', 'master'],
+      workingDirectory: environment.webUiGoldensRepositoryDirectory.path,
+      mustSucceed: true,
+    );
+    await runProcess(
+      'git',
+      <String>['checkout', _revision],
+      workingDirectory: environment.webUiGoldensRepositoryDirectory.path,
+      mustSucceed: true,
+    );
+  }
+
+  Future<String> _getLocalRevision() async {
+    final io.File head = io.File(path.join(
+      environment.webUiGoldensRepositoryDirectory.path, '.git', 'HEAD'
+    ));
+
+    if (!head.existsSync()) {
+      return null;
+    }
+
+    return head.readAsStringSync().trim();
+  }
+}

lib/web_ui/dev/goldens_lock.yaml

+repository: https://github.com/flutter/goldens.git
+revision: dd993a32c23c5c542f083134467e7cda09cac975

lib/web_ui/dev/test_platform.dart

@@ -147,10 +147,28 @@ class BrowserPlatform extends PlatformPlugin {
   }
 
   Future<String> _diffScreenshot(String filename, bool write, [ Map<String, dynamic> region ]) async {
-    const String _kGoldensDirectory = 'test/golden_files';
+    String goldensDirectory;
+    if (filename.startsWith('__local__')) {
+      filename = filename.substring('__local__/'.length);
+      goldensDirectory = p.join(
+        env.environment.webUiRootDir.path,
+        'test',
+        'golden_files',
+      );
+    } else {
+      await fetchGoldens();
+      goldensDirectory = p.join(
+        env.environment.webUiGoldensRepositoryDirectory.path,
+        'engine',
+        'web',
+      );
+    }
 
     // Bail out fast if golden doesn't exist, and user doesn't want to create it.
-    final File file = File(p.join(_kGoldensDirectory, filename));
+    final File file = File(p.join(
+      goldensDirectory,
+      filename,
+    ));
     if (!file.existsSync() && !write) {
       return '''
 Golden file $filename does not exist.

lib/web_ui/dev/utils.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:io' as io;
 
+import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
 
 import 'environment.dart';
@@ -31,17 +32,54 @@ class FilePath {
   String toString() => _absolutePath;
 }
 
+/// Runs [executable] merging its output into the current process' standard out and standard error.
 Future<int> runProcess(
   String executable,
   List<String> arguments, {
   String workingDirectory,
+  bool mustSucceed: false,
 }) async {
   final io.Process process = await io.Process.start(
     executable,
     arguments,
     workingDirectory: workingDirectory,
   );
-  return _forwardIOAndWait(process);
+  final int exitCode = await _forwardIOAndWait(process);
+  if (mustSucceed && exitCode != 0) {
+    throw ProcessException(
+      description: 'Sub-process failed.',
+      executable: executable,
+      arguments: arguments,
+      workingDirectory: workingDirectory,
+      exitCode: exitCode,
+    );
+  }
+  return exitCode;
+}
+
+/// Runs [executable] and returns its standard output as a string.
+///
+/// If the process fails, throws a [ProcessException].
+Future<String> evalProcess(
+  String executable,
+  List<String> arguments, {
+  String workingDirectory,
+}) async {
+  final io.ProcessResult result = await io.Process.run(
+    executable,
+    arguments,
+    workingDirectory: workingDirectory,
+  );
+  if (result.exitCode != 0) {
+    throw ProcessException(
+      description: result.stderr,
+      executable: executable,
+      arguments: arguments,
+      workingDirectory: workingDirectory,
+      exitCode: result.exitCode,
+    );
+  }
+  return result.stdout;
 }
 
 Future<int> _forwardIOAndWait(io.Process process) {
@@ -53,3 +91,31 @@ Future<int> _forwardIOAndWait(io.Process process) {
     return exitCode;
   });
 }
+
+@immutable
+class ProcessException implements Exception {
+  ProcessException({
+    @required this.description,
+    @required this.executable,
+    @required this.arguments,
+    @required this.workingDirectory,
+    @required this.exitCode,
+  });
+
+  final String description;
+  final String executable;
+  final List<String> arguments;
+  final String workingDirectory;
+  final int exitCode;
+
+  @override
+  String toString() {
+    final StringBuffer message = StringBuffer();
+    message
+      ..writeln(description)
+      ..writeln('Command: $executable ${arguments.join(' ')}')
+      ..writeln('Working directory: ${workingDirectory ?? io.Directory.current.path}')
+      ..writeln('Exit code: $exitCode');
+    return '$message';
+  }
+}