[web] Add --watch flag to 'felt test'

lib/web_ui/dev/README.md

@@ -7,7 +7,7 @@
 `felt` supports multiple commands as follows:
 
 1. **`felt check-licenses`**: Checks that all Dart and JS source code files contain the correct license headers.
-2. **`felt test`**: Runs all or some tests depending on the passed arguments.
+2. **`felt test`**: Runs all or some tests depending on the passed arguments. It supports a watch mode for convenience.
 3. **`felt build`**: Builds the engine locally so it can be used by Flutter apps. It also supports a watch mode for more convenience.
 
 You could also run `felt help` or `felt help <command>` to get more information about the available commands and arguments.
@@ -43,6 +43,18 @@ To run all tests on Chrome. This will run both integration tests and the unit te
 felt test
 ```
 
+To run a specific test:
+
+```
+felt test test/engine/util_test.dart
+```
+
+To enable watch mode so that the test re-runs on every change:
+
+```
+felt test --watch test/engine/util_test.dart
+```
+
 To run unit tests only:
 
 ```

lib/web_ui/dev/build.dart

@@ -6,12 +6,11 @@
 import 'dart:async';
 
 import 'package:args/command_runner.dart';
-import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
-import 'package:watcher/watcher.dart';
 
 import 'environment.dart';
 import 'utils.dart';
+import 'watcher.dart';
 
 class BuildCommand extends Command<bool> with ArgUtils {
   BuildCommand() {
@@ -37,7 +36,7 @@ class BuildCommand extends Command<bool> with ArgUtils {
     final FilePath libPath = FilePath.fromWebUi('lib');
     final Pipeline buildPipeline = Pipeline(steps: <PipelineStep>[
       gn,
-      () => ninja(),
+      ninja,
     ]);
     await buildPipeline.start();
 
@@ -77,124 +76,3 @@ Future<void> ninja() {
     environment.hostDebugUnoptDir.path,
   ]);
 }
-
-enum PipelineStatus {
-  idle,
-  started,
-  stopping,
-  stopped,
-  error,
-  done,
-}
-
-typedef PipelineStep = Future<void> Function();
-
-class Pipeline {
-  Pipeline({@required this.steps});
-
-  final Iterable<PipelineStep> steps;
-
-  Future<dynamic> _currentStepFuture;
-
-  PipelineStatus status = PipelineStatus.idle;
-
-  Future<void> start() async {
-    status = PipelineStatus.started;
-    try {
-      for (PipelineStep step in steps) {
-        if (status != PipelineStatus.started) {
-          break;
-        }
-        _currentStepFuture = step();
-        await _currentStepFuture;
-      }
-      status = PipelineStatus.done;
-    } catch (error, stackTrace) {
-      status = PipelineStatus.error;
-      print('Error in the pipeline: $error');
-      print(stackTrace);
-    } finally {
-      _currentStepFuture = null;
-    }
-  }
-
-  Future<void> stop() {
-    status = PipelineStatus.stopping;
-    return (_currentStepFuture ?? Future<void>.value(null)).then((_) {
-      status = PipelineStatus.stopped;
-    });
-  }
-}
-
-typedef WatchEventPredicate = bool Function(WatchEvent event);
-
-class PipelineWatcher {
-  PipelineWatcher({
-    @required this.dir,
-    @required this.pipeline,
-    this.ignore,
-  }) : watcher = DirectoryWatcher(dir);
-
-  /// The path of the directory to watch for changes.
-  final String dir;
-
-  /// The pipeline to be executed when an event is fired by the watcher.
-  final Pipeline pipeline;
-
-  /// Used to watch a directory for any file system changes.
-  final DirectoryWatcher watcher;
-
-  /// A callback that determines whether to rerun the pipeline or not for a
-  /// given [WatchEvent] instance.
-  final WatchEventPredicate ignore;
-
-  void start() {
-    watcher.events.listen(_onEvent);
-  }
-
-  int _pipelineRunCount = 0;
-  Timer _scheduledPipeline;
-
-  void _onEvent(WatchEvent event) {
-    if (ignore != null && ignore(event)) {
-      return;
-    }
-
-    final String relativePath = path.relative(event.path, from: dir);
-    print('- [${event.type}] ${relativePath}');
-
-    _pipelineRunCount++;
-    _scheduledPipeline?.cancel();
-    _scheduledPipeline = Timer(const Duration(milliseconds: 100), () {
-      _scheduledPipeline = null;
-      _runPipeline();
-    });
-  }
-
-  void _runPipeline() {
-    int runCount;
-    switch (pipeline.status) {
-      case PipelineStatus.started:
-        pipeline.stop().then((_) {
-          runCount = _pipelineRunCount;
-          pipeline.start().then((_) => _pipelineDone(runCount));
-        });
-        break;
-
-      case PipelineStatus.stopping:
-        // We are already trying to stop the pipeline. No need to do anything.
-        break;
-
-      default:
-        runCount = _pipelineRunCount;
-        pipeline.start().then((_) => _pipelineDone(runCount));
-        break;
-    }
-  }
-
-  void _pipelineDone(int pipelineRunCount) {
-    if (pipelineRunCount == _pipelineRunCount) {
-      print('*** Done! ***');
-    }
-  }
-}

lib/web_ui/dev/test_runner.dart

@@ -26,6 +26,7 @@ import 'safari_installation.dart';
 import 'supported_browsers.dart';
 import 'test_platform.dart';
 import 'utils.dart';
+import 'watcher.dart';
 
 /// The type of tests requested by the tool user.
 enum TestTypesRequested {
@@ -48,6 +49,12 @@ class TestCommand extends Command<bool> with ArgUtils {
             'opportunity to add breakpoints or inspect loaded code before '
             'running the code.',
       )
+      ..addFlag(
+        'watch',
+        abbr: 'w',
+        help: 'Run in watch mode so the tests re-run whenever a change is '
+            'made.',
+      )
       ..addFlag(
         'unit-tests-only',
         defaultsTo: false,
@@ -100,6 +107,8 @@ class TestCommand extends Command<bool> with ArgUtils {
   @override
   final String description = 'Run tests.';
 
+  bool get isWatchMode => boolArg('watch');
+
   TestTypesRequested testTypesRequested = null;
 
   /// How many dart2js build tasks are running at the same time.
@@ -146,25 +155,80 @@ class TestCommand extends Command<bool> with ArgUtils {
       await macOsInfo.printInformation();
     }
 
-    switch (testTypesRequested) {
-      case TestTypesRequested.unit:
-        return runUnitTests();
-      case TestTypesRequested.integration:
-        return runIntegrationTests();
-      case TestTypesRequested.all:
-        if (runAllTests && isIntegrationTestsAvailable) {
-          bool unitTestResult = await runUnitTests();
-          bool integrationTestResult = await runIntegrationTests();
-          if (integrationTestResult != unitTestResult) {
-            print('Tests run. Integration tests passed: $integrationTestResult '
-                'unit tests passed: $unitTestResult');
+    final Pipeline testPipeline = Pipeline(steps: <PipelineStep>[
+      () async => clearTerminalScreen(),
+      () => runTestsOfType(testTypesRequested),
+    ]);
+    await testPipeline.start();
+
+    if (isWatchMode) {
+      final FilePath dir = FilePath.fromWebUi('');
+      print('');
+      print('Initial test run is done!');
+      print('Watching ${dir.relativeToCwd}/lib and ${dir.relativeToCwd}/test to re-run tests');
+      print('');
+      PipelineWatcher(
+        dir: dir.absolute,
+        pipeline: testPipeline,
+        ignore: (event) {
+          // Ignore font files that are copied whenever tests run.
+          if (event.path.endsWith('.ttf')) {
+            return true;
+          }
+
+          // Ignore auto-generated JS files.
+          // The reason we are using `.contains()` instead of `.endsWith()` is
+          // because the auto-generated files could end with any of the
+          // following:
+          //
+          // - browser_test.dart.js
+          // - browser_test.dart.js.map
+          // - browser_test.dart.js.deps
+          if (event.path.contains('browser_test.dart.js')) {
+            return true;
           }
-          return integrationTestResult && unitTestResult;
-        } else {
-          return await runUnitTests();
+
+          // React to changes in lib/ and test/ folders.
+          final String relativePath = path.relative(event.path, from: dir.absolute);
+          if (relativePath.startsWith('lib/') || relativePath.startsWith('test/')) {
+            return false;
+          }
+
+          // Ignore anything else.
+          return true;
         }
+      ).start();
+      // Return a never-ending future.
+      return Completer<bool>().future;
+    } else {
+      return true;
+    }
+  }
+
+  Future<bool> runTestsOfType(TestTypesRequested testTypesRequested) async {
+    try {
+      switch (testTypesRequested) {
+        case TestTypesRequested.unit:
+          return runUnitTests();
+        case TestTypesRequested.integration:
+          return runIntegrationTests();
+        case TestTypesRequested.all:
+          if (runAllTests && isIntegrationTestsAvailable) {
+            bool unitTestResult = await runUnitTests();
+            bool integrationTestResult = await runIntegrationTests();
+            if (integrationTestResult != unitTestResult) {
+              print('Tests run. Integration tests passed: $integrationTestResult '
+                  'unit tests passed: $unitTestResult');
+            }
+            return integrationTestResult && unitTestResult;
+          } else {
+            return await runUnitTests();
+          }
+      }
+      throw UnimplementedError('Unknown test type requested: $testTypesRequested');
+    } on TestFailureException {
+      return true;
     }
-    return false;
   }
 
   Future<bool> runIntegrationTests() async {
@@ -499,7 +563,12 @@ class TestCommand extends Command<bool> with ArgUtils {
 
   void _checkExitCode() {
     if (io.exitCode != 0) {
-      throw ToolException('Process exited with exit code ${io.exitCode}.');
+      if (isWatchMode) {
+        io.exitCode = 0;
+        throw TestFailureException();
+      } else {
+        throw ToolException('Process exited with exit code ${io.exitCode}.');
+      }
     }
   }
 
@@ -729,3 +798,5 @@ class TestBuildInput {
 
   TestBuildInput(this.path, {this.forCanvasKit = false});
 }
+
+class TestFailureException implements Exception {}

lib/web_ui/dev/utils.dart

@@ -14,6 +14,16 @@ import 'package:path/path.dart' as path;
 import 'environment.dart';
 import 'exceptions.dart';
 
+/// Clears the terminal screen and places the cursor at the top left corner.
+///
+/// This works on Linux and Mac. On Windows, it's a no-op.
+void clearTerminalScreen() {
+  if (!io.Platform.isWindows) {
+    // See: https://en.wikipedia.org/wiki/ANSI_escape_code#CSI_sequences
+    print("\x1B[2J\x1B[1;2H");
+  }
+}
+
 class FilePath {
   FilePath.fromCwd(String relativePath)
       : _absolutePath = path.absolute(relativePath);