initial work on coverage generating script for tool (#29494)

.gitignore

@@ -85,6 +85,9 @@ unlinked_spec.ds
 **/ios/ServiceDefinitions.json
 **/ios/Runner/GeneratedPluginRegistrant.*
 
+# Coverage
+coverage/
+
 # Exceptions to above rules.
 !**/ios/**/default.mode1v3
 !**/ios/**/default.mode2v3

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

@@ -34,10 +34,11 @@ class CoverageCollector extends TestWatcher {
   }
 
   void _addHitmap(Map<String, dynamic> hitmap) {
-    if (_globalHitmap == null)
+    if (_globalHitmap == null) {
       _globalHitmap = hitmap;
-    else
+    } else {
       coverage.mergeHitmaps(hitmap, _globalHitmap);
+    }
   }
 
   /// Collects coverage for the given [Process] using the given `port`.
@@ -91,8 +92,9 @@ class CoverageCollector extends TestWatcher {
     Directory coverageDirectory,
   }) async {
     printTrace('formating coverage data');
-    if (_globalHitmap == null)
+    if (_globalHitmap == null) {
       return null;
+    }
     if (formatter == null) {
       final coverage.Resolver resolver = coverage.Resolver(packagesPath: PackageMap.globalPackagesPath);
       final String packagePath = fs.currentDirectory.path;

packages/flutter_tools/test/integration/test_driver.dart

@@ -511,6 +511,9 @@ class FlutterRunTestDriver extends FlutterTestDriver {
   }
 
   Future<int> detach() async {
+    if (_process == null) {
+      return 0;
+    }
     if (_vmService != null) {
       _debugPrint('Closing VM service...');
       _vmService.dispose();

packages/flutter_tools/tool/tool_coverage.dart

@@ -0,0 +1,167 @@
+// 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 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:args/args.dart';
+import 'package:flutter_tools/src/context_runner.dart';
+import 'package:flutter_tools/src/project.dart';
+import 'package:flutter_tools/src/test/coverage_collector.dart';
+import 'package:pool/pool.dart';
+import 'package:path/path.dart' as path;
+
+final ArgParser argParser = ArgParser()
+  ..addOption('output-html',
+    defaultsTo: 'coverage/report.html',
+    help: 'The output path for the genhtml report.'
+  )
+  ..addOption('output-lcov',
+    defaultsTo: 'coverage/lcov.info',
+    help: 'The output path for the lcov data.'
+  )
+  ..addOption('test-directory',
+    defaultsTo: 'test/',
+    help: 'The path to the test directory.'
+  )
+  ..addOption('packages',
+    defaultsTo: '.packages',
+    help: 'The path to the .packages file.'
+  )
+  ..addOption('genhtml',
+    defaultsTo: 'genhtml',
+    help: 'The genhtml executable.');
+
+
+/// Generates an html coverage report for the flutter_tool.
+///
+/// Example invocation:
+///
+///    dart tool/tool_coverage.dart --packages=.packages --test-directory=test
+Future<void> main(List<String> arguments) async {
+  final ArgResults argResults = argParser.parse(arguments);
+  await runInContext(() async {
+    final CoverageCollector coverageCollector = CoverageCollector(
+      flutterProject: await FlutterProject.current(),
+    );
+    /// A temp directory to create synthetic test files in.
+    final Directory tempDirectory = Directory.systemTemp.createTempSync('_flutter_coverage')
+      ..createSync();
+    final String flutterRoot = File(Platform.script.toFilePath()).parent.parent.parent.parent.path;
+    await ToolCoverageRunner(tempDirectory, coverageCollector, flutterRoot, argResults).collectCoverage();
+  });
+}
+
+class ToolCoverageRunner {
+  ToolCoverageRunner(
+    this.tempDirectory,
+    this.coverageCollector,
+    this.flutterRoot,
+    this.argResults,
+  );
+
+  final ArgResults argResults;
+  final Pool pool = Pool(Platform.numberOfProcessors);
+  final Directory tempDirectory;
+  final CoverageCollector coverageCollector;
+  final String flutterRoot;
+
+  Future<void> collectCoverage() async {
+    final List<Future<void>> pending = <Future<void>>[];
+
+    final Directory testDirectory = Directory(argResults['test-directory']);
+    final List<FileSystemEntity> fileSystemEntities = testDirectory.listSync(recursive: true);
+    for (FileSystemEntity fileSystemEntity in fileSystemEntities) {
+      if (!fileSystemEntity.path.endsWith('_test.dart')) {
+        continue;
+      }
+      pending.add(_runTest(fileSystemEntity));
+    }
+    await Future.wait(pending);
+
+    final String lcovData = await coverageCollector.finalizeCoverage();
+    final String outputLcovPath = argResults['output-lcov'];
+    final String outputHtmlPath = argResults['output-html'];
+    final String genHtmlExecutable = argResults['genhtml'];
+    File(outputLcovPath)
+      ..createSync(recursive: true)
+      ..writeAsStringSync(lcovData);
+    await Process.run(genHtmlExecutable, <String>[outputLcovPath, '-o', outputHtmlPath], runInShell: true);
+  }
+
+  // Creates a synthetic test file to wrap the test main in a group invocation.
+  // This will set up several fields used by the test methods on the context. Normally
+  // this would be handled automatically by the test runner, but since we're executing
+  // the files directly with dart we need to handle it manually.
+  String _createTest(File testFile) {
+    final File fakeTest = File(path.join(tempDirectory.path, testFile.path))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('''
+import "package:test/test.dart";
+import "${path.absolute(testFile.path)}" as entrypoint;
+
+void main() {
+  group('', entrypoint.main);
+}
+''');
+    return fakeTest.path;
+  }
+
+  Future<void> _runTest(File testFile) async {
+    final PoolResource resource = await pool.request();
+    final String testPath = _createTest(testFile);
+    final int port = await _findPort();
+    final Uri coverageUri = Uri.parse('http://127.0.0.1:$port');
+    final Completer<void> completer = Completer<void>();
+    final String packagesPath = argResults['packages'];
+    final Process testProcess = await Process.start(
+      Platform.resolvedExecutable,
+      <String>[
+        '--packages=$packagesPath',
+        '--pause-isolates-on-exit',
+        '--enable-asserts',
+        '--enable-vm-service=${coverageUri.port}',
+        testPath,
+      ],
+      runInShell: true,
+      environment: <String, String>{
+        'FLUTTER_ROOT': flutterRoot,
+      }).timeout(const Duration(seconds: 30));
+    testProcess.stdout
+      .transform(utf8.decoder)
+      .transform(const LineSplitter())
+      .listen((String line) {
+        print(line);
+        if (line.contains('All tests passed') || line.contains('Some tests failed')) {
+          completer.complete(null);
+        }
+      });
+    try {
+      await completer.future;
+      await coverageCollector.collectCoverage(testProcess, coverageUri).timeout(const Duration(seconds: 30));
+      testProcess?.kill();
+    } on TimeoutException {
+      print('Failed to collect coverage for ${testFile.path} after 30 seconds');
+    } finally {
+      resource.release();
+    }
+  }
+
+  Future<int> _findPort() async {
+    int port = 0;
+    ServerSocket serverSocket;
+    try {
+      serverSocket = await ServerSocket.bind(InternetAddress.loopbackIPv4.address, 0);
+      port = serverSocket.port;
+    } catch (e) {
+      // Failures are signaled by a return value of 0 from this function.
+      print('_findPort failed: $e');
+    }
+    if (serverSocket != null) {
+      await serverSocket.close();
+    }
+    return port;
+  }
+}