enable lint prefer_foreach (#12674)

* enable lint prefer_foreach

* fix tests

analysis_options.yaml

@@ -119,7 +119,7 @@ linter:
     # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
     - prefer_final_fields
     - prefer_final_locals
-    # - prefer_foreach # not yet tested
+    - prefer_foreach
     # - prefer_function_declarations_over_variables # not yet tested
     - prefer_initializing_formals
     # - prefer_interpolation_to_compose_strings # not yet tested

analysis_options_repo.yaml

@@ -113,7 +113,7 @@ linter:
     # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
     - prefer_final_fields
     - prefer_final_locals
-    # - prefer_foreach # not yet tested
+    - prefer_foreach
     # - prefer_function_declarations_over_variables # not yet tested
     - prefer_initializing_formals
     # - prefer_interpolation_to_compose_strings # not yet tested

packages/flutter/lib/src/gestures/multidrag.dart

@@ -293,8 +293,7 @@ abstract class MultiDragGestureRecognizer<T extends MultiDragPointerState> exten
 
   @override
   void dispose() {
-    for (int pointer in _pointers.keys.toList())
-      _removeState(pointer);
+    _pointers.keys.toList().forEach(_removeState);
     assert(_pointers.isEmpty);
     _pointers = null;
     super.dispose();

packages/flutter/lib/src/gestures/multitap.dart

@@ -199,9 +199,7 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
   }
 
   void _clearTrackers() {
-    final List<_TapTracker> localTrackers = new List<_TapTracker>.from(_trackers.values);
-    for (_TapTracker tracker in localTrackers)
-      _reject(tracker);
+    _trackers.values.toList().forEach(_reject);
     assert(_trackers.isEmpty);
   }
 

packages/flutter/lib/src/painting/text_style.dart

@@ -173,10 +173,10 @@ const String _kDefaultDebugLabel = 'unknown';
 /// If the package internally uses the font it defines, it should still specify
 /// the `package` argument when creating the text style as in the example above.
 ///
-/// A package can also provide font files without declaring a font in its 
-/// `pubspec.yaml`. These files should then be in the `lib/` folder of the 
-/// package. The font files will not automatically be bundled in the app, instead 
-/// the app can use these selectively when declaring a font. Suppose a package 
+/// A package can also provide font files without declaring a font in its
+/// `pubspec.yaml`. These files should then be in the `lib/` folder of the
+/// package. The font files will not automatically be bundled in the app, instead
+/// the app can use these selectively when declaring a font. Suppose a package
 /// named `my_package` has:
 ///
 /// ```
@@ -197,7 +197,7 @@ const String _kDefaultDebugLabel = 'unknown';
 ///
 /// The `lib/` is implied, so it should not be included in the asset path.
 ///
-/// In this case, since the app locally defines the font, the TextStyle is 
+/// In this case, since the app locally defines the font, the TextStyle is
 /// created without the `package` argument:
 ///
 ///```dart
@@ -709,8 +709,7 @@ class TextStyle extends Diagnosticable {
 
     final bool styleSpecified = styles.any((DiagnosticsNode n) => !n.isFiltered(DiagnosticLevel.info));
     properties.add(new DiagnosticsProperty<bool>('${prefix}inherit', inherit, level: (!styleSpecified && inherit) ? DiagnosticLevel.fine : DiagnosticLevel.info));
-    for (DiagnosticsNode style in styles)
-      properties.add(style);
+    styles.forEach(properties.add);
 
     if (!styleSpecified)
       properties.add(new FlagProperty('inherit', value: inherit, ifTrue: '$prefix<all styles inherited>', ifFalse: '$prefix<no style specified>'));

packages/flutter/lib/src/rendering/object.dart

@@ -2736,9 +2736,7 @@ abstract class ContainerRenderObjectMixin<ChildType extends RenderObject, Parent
 
   /// Add all the children to the end of this render object's child list.
   void addAll(List<ChildType> children) {
-    if (children != null)
-      for (ChildType child in children)
-        add(child);
+    children?.forEach(add);
   }
 
   void _removeFromChildList(ChildType child) {
@@ -2923,7 +2921,7 @@ class FlutterErrorDetailsForRendering extends FlutterErrorDetails {
 
 /// Describes the semantics information a [RenderObject] wants to add to its
 /// parent.
-/// 
+///
 /// It has two notable subclasses:
 ///  * [_InterestingSemanticsFragment] describing actual semantic information to
 ///    be added to the parent.

packages/flutter/lib/src/rendering/semantics.dart

@@ -438,10 +438,7 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
 
   @override
   void redepthChildren() {
-    if (_children != null) {
-      for (SemanticsNode child in _children)
-        redepthChild(child);
-    }
+    _children?.forEach(redepthChild);
   }
 
   @override

packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart

@@ -219,8 +219,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
   @override
   void removeAll() {
     super.removeAll();
-    for (RenderBox child in _keepAliveBucket.values)
-      dropChild(child);
+    _keepAliveBucket.values.forEach(dropChild);
     _keepAliveBucket.clear();
   }
 
@@ -274,15 +273,13 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
   @override
   void redepthChildren() {
     super.redepthChildren();
-    for (RenderBox child in _keepAliveBucket.values)
-      redepthChild(child);
+    _keepAliveBucket.values.forEach(redepthChild);
   }
 
   @override
   void visitChildren(RenderObjectVisitor visitor) {
     super.visitChildren(visitor);
-    for (RenderBox child in _keepAliveBucket.values)
-      visitor(child);
+    _keepAliveBucket.values.forEach(visitor);
   }
 
   @override

packages/flutter/lib/src/rendering/table.dart

@@ -384,10 +384,7 @@ class RenderTable extends RenderBox {
     _configuration = configuration;
     _defaultVerticalAlignment = defaultVerticalAlignment;
     _textBaseline = textBaseline;
-    if (children != null) {
-      for (List<RenderBox> row in children)
-        addRow(row);
-    }
+    children?.forEach(addRow);
   }
 
   // Children are stored in row-major order.
@@ -628,8 +625,7 @@ class RenderTable extends RenderBox {
       y += 1;
     }
     // drop all the lost children
-    for (RenderBox oldChild in lostChildren)
-      dropChild(oldChild);
+    lostChildren.forEach(dropChild);
     // update our internal values
     _columns = columns;
     _rows = cells.length ~/ columns;
@@ -652,8 +648,7 @@ class RenderTable extends RenderBox {
     _children.clear();
     _columns = cells.isNotEmpty ? cells.first.length : 0;
     _rows = 0;
-    for (List<RenderBox> row in cells)
-      addRow(row);
+    cells.forEach(addRow);
     assert(_children.length == rows * columns);
   }
 

packages/flutter/lib/src/widgets/framework.dart

@@ -1736,8 +1736,7 @@ class _InactiveElements {
     final List<Element> elements = _elements.toList()..sort(Element._sort);
     _elements.clear();
     try {
-      for (Element element in elements.reversed)
-        _unmount(element);
+      elements.reversed.forEach(_unmount);
     } finally {
       assert(_elements.isEmpty);
       _locked = false;

packages/flutter/lib/src/widgets/navigator.dart

@@ -791,8 +791,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
         }());
         push(_routeNamed(Navigator.defaultRouteName));
       } else {
-        for (Route<dynamic> route in plannedInitialRoutes)
-          push(route);
+        plannedInitialRoutes.forEach(push);
       }
     } else {
       Route<dynamic> route;
@@ -1328,8 +1327,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
         absorber?.absorbing = true;
       });
     }
-    for (int pointer in _activePointers.toList())
-      WidgetsBinding.instance.cancelPointer(pointer);
+    _activePointers.toList().forEach(WidgetsBinding.instance.cancelPointer);
   }
 
   @override

packages/flutter/test/foundation/diagnostics_test.dart

@@ -36,8 +36,7 @@ class TestTree extends Object with DiagnosticableTreeMixin {
     if (style != null)
       properties.defaultDiagnosticsTreeStyle = style;
 
-    for (DiagnosticsNode property in this.properties)
-      properties.add(property);
+    this.properties.forEach(properties.add);
   }
 }
 

packages/flutter/test/scheduler/scheduler_test.dart

@@ -28,8 +28,7 @@ void main() {
       scheduler.scheduleTask(() { executedTasks.add(x); }, Priority.idle + x);
     }
 
-    for (int x in input)
-      scheduleAddingTask(x);
+    input.forEach(scheduleAddingTask);
 
     strategy.allowedPriority = 100;
     for (int i = 0; i < 3; i += 1)

packages/flutter/test/widgets/linked_scroll_view_test.dart

@@ -26,13 +26,11 @@ class LinkedScrollController extends ScrollController {
 
   void setParent(ScrollController newParent) {
     if (_parent != null) {
-      for (ScrollPosition position in positions)
-        _parent.detach(position);
+      positions.forEach(_parent.detach);
     }
     _parent = newParent;
     if (_parent != null) {
-      for (ScrollPosition position in positions)
-        _parent.attach(position);
+      positions.forEach(_parent.attach);
     }
   }
 
@@ -54,8 +52,7 @@ class LinkedScrollController extends ScrollController {
   @override
   void dispose() {
     if (_parent != null) {
-      for (ScrollPosition position in positions)
-        _parent.detach(position);
+      positions.forEach(_parent.detach);
     }
     super.dispose();
   }

packages/flutter_tools/lib/src/asset.dart

@@ -194,9 +194,7 @@ class AssetBundle {
 
   void dump() {
     printTrace('Dumping AssetBundle:');
-    for (String archivePath in entries.keys.toList()..sort()) {
-      printTrace(archivePath);
-    }
+    (entries.keys.toList()..sort()).forEach(printTrace);
   }
 }
 

packages/flutter_tools/lib/src/base/net.dart

@@ -55,8 +55,7 @@ Future<List<int>> _attempt(Uri url) async {
   printTrace('Received response from server, collecting bytes...');
   try {
     final BytesBuilder responseBody = new BytesBuilder(copy: false);
-    await for (List<int> chunk in response)
-      responseBody.add(chunk);
+    await response.forEach(responseBody.add);
     return responseBody.takeBytes();
   } on IOException catch (error) {
     printTrace('Download error: $error');

packages/flutter_tools/lib/src/base/utils.dart

@@ -142,10 +142,8 @@ class ItemListNotifier<T> {
 
     _items = updatedSet;
 
-    for (T item in addedItems)
-      _addedController.add(item);
-    for (T item in removedItems)
-      _removedController.add(item);
+    addedItems.forEach(_addedController.add);
+    removedItems.forEach(_removedController.add);
   }
 
   /// Close the streams.

packages/flutter_tools/lib/src/compile.dart

@@ -131,8 +131,7 @@ class ResidentCompiler {
 
     final String inputKey = new Uuid().generateV4();
     _server.stdin.writeln('recompile $inputKey');
-    for (String invalidatedFile in invalidatedFiles)
-      _server.stdin.writeln(invalidatedFile);
+    invalidatedFiles.forEach(_server.stdin.writeln);
     _server.stdin.writeln(inputKey);
 
     return stdoutHandler.outputFilename.future;

packages/flutter_tools/lib/src/devfs.dart

@@ -478,8 +478,7 @@ class DevFS {
       }
       // No need to send source files because all compilation is done on the
       // host and result of compilation is single kernel file.
-      for (Uri fileUri in filesUris)
-        dirtyEntries.remove(fileUri);
+      filesUris.forEach(dirtyEntries.remove);
       printTrace('Compiling dart to kernel with ${invalidatedFiles.length} updated files');
       final String compiledBinary = fullRestart
         ? await compile(

packages/flutter_tools/test/base/net_test.dart

@@ -91,7 +91,7 @@ class MockHttpClientRequest implements io.HttpClientRequest {
   }
 }
 
-class MockHttpClientResponse implements io.HttpClientResponse {
+class MockHttpClientResponse extends Stream<List<int>> implements io.HttpClientResponse {
   MockHttpClientResponse(this.statusCode);
 
   @override

packages/flutter_tools/test/compile_test.dart

@@ -45,7 +45,7 @@ void main() {
       final String output = await compile(sdkRoot: '/path/to/sdkroot',
         mainPath: '/path/to/main.dart'
       );
-      verifyNever(mockFrontendServerStdIn.writeln(any));
+      expect(mockFrontendServerStdIn.getAndClear(), isEmpty);
       expect(logger.traceText, equals('compile debug message: line1\ncompile debug message: line2\n'));
       expect(output, equals('/path/to/main.dart.dill'));
     }, overrides: <Type, Generator>{
@@ -64,7 +64,7 @@ void main() {
       final String output = await compile(sdkRoot: '/path/to/sdkroot',
         mainPath: '/path/to/main.dart'
       );
-      verifyNever(mockFrontendServerStdIn.writeln(any));
+      expect(mockFrontendServerStdIn.getAndClear(), isEmpty);
       expect(logger.traceText, equals('compile debug message: line1\ncompile debug message: line2\n'));
       expect(output, equals(null));
     }, overrides: <Type, Generator>{
@@ -110,7 +110,7 @@ void main() {
       final String output = await generator.recompile(
         '/path/to/main.dart', null /* invalidatedFiles */
       );
-      verify(mockFrontendServerStdIn.writeln('compile /path/to/main.dart'));
+      expect(mockFrontendServerStdIn.getAndClear(), 'compile /path/to/main.dart\n');
       verifyNoMoreInteractions(mockFrontendServerStdIn);
       expect(logger.traceText, equals('compile debug message: line1\ncompile debug message: line2\n'));
       expect(output, equals('/path/to/main.dart.dill'));
@@ -125,12 +125,13 @@ void main() {
       when(mockFrontendServer.stdout).thenReturn(streamController.stream);
       streamController.add(UTF8.encode('result abc\nline0\nline1\nabc /path/to/main.dart.dill\n'));
       await generator.recompile('/path/to/main.dart', null /* invalidatedFiles */);
-      verify(mockFrontendServerStdIn.writeln('compile /path/to/main.dart'));
+      expect(mockFrontendServerStdIn.getAndClear(), 'compile /path/to/main.dart\n');
 
       await _recompile(streamController, generator, mockFrontendServerStdIn,
         'result abc\nline1\nline2\nabc /path/to/main.dart.dill\n');
 
       verifyNoMoreInteractions(mockFrontendServerStdIn);
+      expect(mockFrontendServerStdIn.getAndClear(), isEmpty);
       expect(logger.traceText, equals(
         'compile debug message: line0\ncompile debug message: line1\n'
         'compile debug message: line1\ncompile debug message: line2\n'
@@ -148,7 +149,7 @@ void main() {
         'result abc\nline0\nline1\nabc /path/to/main.dart.dill\n'
       ));
       await generator.recompile('/path/to/main.dart', null /* invalidatedFiles */);
-      verify(mockFrontendServerStdIn.writeln('compile /path/to/main.dart'));
+      expect(mockFrontendServerStdIn.getAndClear(), 'compile /path/to/main.dart\n');
 
       await _recompile(streamController, generator, mockFrontendServerStdIn,
         'result abc\nline1\nline2\nabc /path/to/main.dart.dill\n');
@@ -156,6 +157,7 @@ void main() {
         'result abc\nline2\nline3\nabc /path/to/main.dart.dill\n');
 
       verifyNoMoreInteractions(mockFrontendServerStdIn);
+      expect(mockFrontendServerStdIn.getAndClear(), isEmpty);
       expect(logger.traceText, equals(
         'compile debug message: line0\ncompile debug message: line1\n'
         'compile debug message: line1\ncompile debug message: line2\n'
@@ -177,15 +179,33 @@ Future<Null> _recompile(StreamController<List<int>> streamController,
   });
   final String output = await generator.recompile(null /* mainPath */, <String>['/path/to/main.dart']);
   expect(output, equals('/path/to/main.dart.dill'));
-  final String recompileCommand = verify(
-    mockFrontendServerStdIn.writeln(captureThat(startsWith('recompile ')))
-  ).captured[0];
-  final String token1 = recompileCommand.split(' ')[1];
-  verify(mockFrontendServerStdIn.writeln('/path/to/main.dart'));
-  verify(mockFrontendServerStdIn.writeln(token1));
+  final String commands = mockFrontendServerStdIn.getAndClear();
+  final RegExp re = new RegExp(r'^recompile (.*)\n/path/to/main.dart\n(.*)\n$');
+  expect(commands, matches(re));
+  final Match match = re.firstMatch(commands);
+  expect(match[1] == match[2], isTrue);
+  mockFrontendServerStdIn._stdInWrites.clear();
 }
 
 class MockProcessManager extends Mock implements ProcessManager {}
 class MockProcess extends Mock implements Process {}
 class MockStream extends Mock implements Stream<List<int>> {}
-class MockStdIn extends Mock implements IOSink {}
+class MockStdIn extends Mock implements IOSink {
+  final StringBuffer _stdInWrites = new StringBuffer();
+
+  String getAndClear() {
+    final String result = _stdInWrites.toString();
+    _stdInWrites.clear();
+    return result;
+  }
+
+  @override
+  void write([Object o = '']) {
+    _stdInWrites.write(o);
+  }
+
+  @override
+  void writeln([Object o = '']) {
+    _stdInWrites.writeln(o);
+  }
+}