Make tool coverage collection resilient to sentinel coverage data (#35186)

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

@@ -184,13 +184,17 @@ class CoverageCollector extends TestWatcher {
   }
 }
 
-Future<Map<String, dynamic>> collect(Uri serviceUri, bool Function(String) libraryPredicate) async {
-  final VMService vmService = await VMService.connect(serviceUri, compression: CompressionOptions.compressionOff);
+Future<VMService> _defaultConnect(Uri serviceUri) {
+  return VMService.connect(serviceUri, compression: CompressionOptions.compressionOff);
+}
+
+Future<Map<String, dynamic>> collect(Uri serviceUri, bool Function(String) libraryPredicate,
+    [Future<VMService> Function(Uri) connector = _defaultConnect]) async {
+  final VMService vmService = await connector(serviceUri);
   await vmService.getVM();
   return _getAllCoverage(vmService, libraryPredicate);
 }
 
-
 Future<Map<String, dynamic>> _getAllCoverage(VMService service, bool Function(String) libraryPredicate) async {
   await service.getVM();
   final List<Map<String, dynamic>> coverage = <Map<String, dynamic>>[];
@@ -203,6 +207,13 @@ Future<Map<String, dynamic>> _getAllCoverage(VMService service, bool Function(St
     final Map<String, Map<String, dynamic>> sourceReports = <String, Map<String, dynamic>>{};
     // For each ScriptRef loaded into the VM, load the corresponding Script and
     // SourceReport object.
+
+    // We may receive such objects as
+    // {type: Sentinel, kind: Collected, valueAsString: <collected>}
+    // that need to be skipped.
+    if (scriptList['scripts'] == null) {
+      continue;
+    }
     for (Map<String, dynamic> script in scriptList['scripts']) {
       if (!libraryPredicate(script['uri'])) {
         continue;

packages/flutter_tools/test/coverage_collector_test.dart

+// 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 'package:flutter_tools/src/base/io.dart';
+import 'package:flutter_tools/src/test/coverage_collector.dart';
+import 'package:flutter_tools/src/vmservice.dart';
+import 'package:mockito/mockito.dart';
+
+import 'src/common.dart';
+
+void main() {
+  MockVMService mockVMService;
+
+  setUp(() {
+    mockVMService = MockVMService();
+  });
+
+  test('Coverage collector Can handle coverage sentinenl data', () async {
+    when(mockVMService.vm.isolates.first.invokeRpcRaw('getScripts', params: anyNamed('params')))
+      .thenAnswer((Invocation invocation) async {
+        return <String, Object>{'type': 'Sentinel', 'kind': 'Collected', 'valueAsString': '<collected>'};
+      });
+    final Map<String, Object> result = await collect(null, (String predicate) => true, (Uri uri) async {
+      return mockVMService;
+    });
+
+    expect(result, <String, Object>{'type': 'CodeCoverage', 'coverage': <Object>[]});
+  });
+}
+
+class MockVMService extends Mock implements VMService {
+  @override
+  final MockVM vm = MockVM();
+}
+
+class MockVM extends Mock implements VM {
+  @override
+  final List<MockIsolate> isolates = <MockIsolate>[ MockIsolate() ];
+}
+
+class MockIsolate extends Mock implements Isolate {}
+
+class MockProcess extends Mock implements Process {
+  final Completer<int>completer = Completer<int>();
+
+  @override
+  Future<int> get exitCode => completer.future;
+}
\ No newline at end of file