Deep linking: automatically push the route hiearchy on load. (#10894)

The main purpose of this PR is to make it so that when you set the
initial route and it's a hierarchical route (e.g. `/a/b/c`), it
implies multiple pushes, one for each step of the route (so in that
case, `/`, `/a`, `/a/b`, and `/a/b/c`, in that order). If any of those
routes don't exist, it falls back to '/'.

As part of doing that, I:

 * Changed the default for MaterialApp.initialRoute to honor the
   actual initial route.

 * Added a MaterialApp.onUnknownRoute for handling bad routes.

 * Added a feature to flutter_driver that allows the host test script
   and the device test app to communicate.

 * Added a test to make sure `flutter drive --route` works.
   (Hopefully that will also prove `flutter run --route` works, though
   this isn't testing the `flutter` tool's side of that. My main
   concern is over whether the engine side works.)

 * Fixed `flutter drive` to output the right target file name.

 * Changed how the stocks app represents its data, so that we can
   show a page for a stock before we know if it exists.

 * Made it possible to show a stock page that doesn't exist. It shows
   a progress indicator if we're loading the data, or else shows a
   message saying it doesn't exist.

 * Changed the pathing structure of routes in stocks to work more
   sanely.

 * Made search in the stocks app actually work (before it only worked
   if we happened to accidentally trigger a rebuild). Added a test.

 * Replaced some custom code in the stocks app with a BackButton.

 * Added a "color" feature to BackButton to support the stocks use case.

 * Spaced out the ErrorWidget text a bit more.

 * Added `RouteSettings.copyWith`, which I ended up not using.

 * Improved the error messages around routing.

While I was in some files I made a few formatting fixes, fixed some
code health issues, and also removed `flaky: true` from some devicelab
tests that have been stable for a while. Also added some documentation
here and there.

dev/benchmarks/microbenchmarks/lib/stocks/animation_bench.dart

@@ -35,7 +35,7 @@ class BenchmarkingBinding extends LiveTestWidgetsFlutterBinding {
 
 Future<Null> main() async {
   assert(false); // don't run this in checked mode! Use --release.
-  stock_data.StockDataFetcher.actuallyFetchData = false;
+  stock_data.StockData.actuallyFetchData = false;
 
   final Stopwatch wallClockWatch = new Stopwatch();
   final Stopwatch cpuWatch = new Stopwatch();

dev/benchmarks/microbenchmarks/lib/stocks/build_bench.dart

@@ -17,7 +17,7 @@ const Duration kBenchmarkTime = const Duration(seconds: 15);
 
 Future<Null> main() async {
   assert(false); // don't run this in checked mode! Use --release.
-  stock_data.StockDataFetcher.actuallyFetchData = false;
+  stock_data.StockData.actuallyFetchData = false;
 
   // This allows us to call onBeginFrame even when the engine didn't request it,
   // and have it actually do something:

dev/benchmarks/microbenchmarks/lib/stocks/layout_bench.dart

@@ -16,7 +16,7 @@ import '../common.dart';
 const Duration kBenchmarkTime = const Duration(seconds: 15);
 
 Future<Null> main() async {
-  stock_data.StockDataFetcher.actuallyFetchData = false;
+  stock_data.StockData.actuallyFetchData = false;
 
   // This allows us to call onBeginFrame even when the engine didn't request it,
   // and have it actually do something:

dev/devicelab/bin/tasks/routing_test.dart

@@ -0,0 +1,85 @@
+// Copyright (c) 2016 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:path/path.dart' as path;
+
+import 'package:flutter_devicelab/framework/adb.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+import 'package:flutter_devicelab/framework/utils.dart';
+
+void main() {
+  task(() async {
+    final Device device = await devices.workingDevice;
+    await device.unlock();
+    final Directory appDir = dir(path.join(flutterDirectory.path, 'dev/integration_tests/ui'));
+    section('TEST WHETHER `flutter drive --route` WORKS');
+    await inDirectory(appDir, () async {
+      return await flutter(
+        'drive',
+        options: <String>['--verbose', '-d', device.deviceId, '--route', '/smuggle-it', 'lib/route.dart'],
+        canFail: false,
+      );
+    });
+    section('TEST WHETHER `flutter run --route` WORKS');
+    await inDirectory(appDir, () async {
+      final Completer<Null> ready = new Completer<Null>();
+      bool ok;
+      print('run: starting...');
+      final Process run = await startProcess(
+        path.join(flutterDirectory.path, 'bin', 'flutter'),
+        <String>['run', '--verbose', '--observatory-port=8888', '-d', device.deviceId, '--route', '/smuggle-it', 'lib/route.dart'],
+      );
+      run.stdout
+        .transform(UTF8.decoder)
+        .transform(const LineSplitter())
+        .listen((String line) {
+          print('run:stdout: $line');
+          if (line == '[            ] For a more detailed help message, press "h". To quit, press "q".') {
+            print('run: ready!');
+            ready.complete();
+            ok ??= true;
+          }
+        });
+      run.stderr
+        .transform(UTF8.decoder)
+        .transform(const LineSplitter())
+        .listen((String line) {
+          stderr.writeln('run:stderr: $line');
+        });
+      run.exitCode.then((int exitCode) { ok = false; });
+      await Future.any<dynamic>(<Future<dynamic>>[ ready.future, run.exitCode ]);
+      if (!ok)
+        throw 'Failed to run test app.';
+      print('drive: starting...');
+      final Process drive = await startProcess(
+        path.join(flutterDirectory.path, 'bin', 'flutter'),
+        <String>['drive', '--use-existing-app', 'http://127.0.0.1:8888/', '--no-keep-app-running', 'lib/route.dart'],
+      );
+      drive.stdout
+        .transform(UTF8.decoder)
+        .transform(const LineSplitter())
+        .listen((String line) {
+          print('drive:stdout: $line');
+        });
+      drive.stderr
+        .transform(UTF8.decoder)
+        .transform(const LineSplitter())
+        .listen((String line) {
+          stderr.writeln('drive:stderr: $line');
+        });
+      int result;
+      result = await drive.exitCode;
+      if (result != 0)
+        throw 'Failed to drive test app (exit code $result).';
+      result = await run.exitCode;
+      if (result != 0)
+        throw 'Received unexpected exit code $result from run process.';
+    });
+    return new TaskResult.success(null);
+  });
+}

dev/devicelab/lib/framework/framework.dart

@@ -26,7 +26,7 @@ bool _isTaskRegistered = false;
 
 /// Registers a [task] to run, returns the result when it is complete.
 ///
-/// Note, the task does not run immediately but waits for the request via the
+/// The task does not run immediately but waits for the request via the
 /// VM service protocol to run it.
 ///
 /// It is ok for a [task] to perform many things. However, only one task can be

dev/devicelab/lib/framework/utils.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:math' as math;
 
 import 'package:args/args.dart';
 import 'package:meta/meta.dart';
@@ -116,7 +117,12 @@ void mkdirs(Directory directory) {
 bool exists(FileSystemEntity entity) => entity.existsSync();
 
 void section(String title) {
-  print('\n••• $title •••');
+  title = '╡ ••• $title ••• ╞';
+  final String line = '═' * math.max((80 - title.length) ~/ 2, 2);
+  String output = '$line$title$line';
+  if (output.length == 79)
+    output += '═';
+  print('\n\n$output\n');
 }
 
 Future<String> getDartVersion() async {
@@ -179,6 +185,7 @@ Future<Process> startProcess(
   _runningProcesses.add(processInfo);
 
   process.exitCode.whenComplete(() {
+    print('\n'); // separate the output of this script from subsequent output to make logs easier to read
     _runningProcesses.remove(processInfo);
   });
 

dev/devicelab/lib/tasks/microbenchmarks.dart

@@ -59,7 +59,7 @@ TaskFunction createMicrobenchmarkTask() {
 }
 
 Future<Process> _startFlutter({
-  String command = 'run',
+  String command: 'run',
   List<String> options: const <String>[],
   bool canFail: false,
   Map<String, String> environment,

dev/devicelab/manifest.yaml

@@ -119,13 +119,18 @@ tasks:
       Builds sample catalog markdown pages and Android screenshots
     stage: devicelab
     required_agent_capabilities: ["has-android-device"]
-    flaky: true
 
   complex_layout_semantics_perf:
     description: >
       Measures duration of building the initial semantics tree.
     stage: devicelab
     required_agent_capabilities: ["linux/android"]
+
+  routing:
+    description: >
+      Verifies that `flutter drive --route` still works. No performance numbers.
+    stage: devicelab
+    required_agent_capabilities: ["linux/android"]
     flaky: true
 
   # iOS on-device tests
@@ -277,7 +282,6 @@ tasks:
       with semantics enabled.
     stage: devicelab
     required_agent_capabilities: ["linux/android"]
-    flaky: true
 
   flutter_gallery__memory_nav:
     description: >

dev/integration_tests/ui/README.md

@@ -1,7 +1,14 @@
 # Flutter UI integration tests
 
-This project contains a collection of non-plugin-dependent UI integration tests.
+This project contains a collection of non-plugin-dependent UI
+integration tests. The device code is in the `lib/` directory, the
+driver code is in the `test_driver/` directory. They work together.
+Normally they are run via the devicelab.
 
 ## keyboard\_resize
 
 Verifies that showing and hiding the keyboard resizes the content.
+
+## routing
+
+Verifies that `flutter drive --route` works correctly.

dev/integration_tests/ui/lib/main.dart

@@ -4,4 +4,4 @@
 
 import 'package:flutter/widgets.dart';
 
-void main() => runApp(const Center(child: const Text('flutter run -t xxx.dart')));
+void main() => runApp(const Center(child: const Text('flutter drive lib/xxx.dart')));

dev/integration_tests/ui/lib/route.dart

@@ -0,0 +1,15 @@
+// Copyright 2017 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:ui' as ui;
+
+import 'package:flutter_driver/driver_extension.dart';
+
+// To use this test: "flutter drive --route '/smuggle-it' lib/route.dart"
+
+void main() {
+  enableFlutterDriverExtension(handler: (String message) async {
+    return ui.window.defaultRouteName;
+  });
+}

dev/integration_tests/ui/test_driver/keyboard_resize_test.dart

@@ -13,8 +13,7 @@ void main() {
     });
 
     tearDownAll(() async {
-      if (driver != null)
-        driver.close();
+      driver?.close();
     });
 
     test('Ensure keyboard dismissal resizes the view to original size', () async {

dev/integration_tests/ui/test_driver/route_test.dart

@@ -0,0 +1,22 @@
+import 'package:flutter_driver/flutter_driver.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('flutter run test --route', () {
+    FlutterDriver driver;
+
+    setUpAll(() async {
+      driver = await FlutterDriver.connect();
+    });
+
+    tearDownAll(() async {
+      driver?.close();
+    });
+
+    test('sanity check flutter drive --route', () async {
+      // This only makes sense if you ran the test as described
+      // in the test file. It's normally run from devicelab.
+      expect(await driver.requestData('route'), '/smuggle-it');
+    });
+  });
+}

dev/manual_tests/lib/material_arc.dart

@@ -475,6 +475,6 @@ class _AnimationDemoState extends State<AnimationDemo> with TickerProviderStateM
 
 void main() {
   runApp(new MaterialApp(
-    home: const AnimationDemo()
+    home: const AnimationDemo(),
   ));
 }

examples/stocks/lib/main.dart

@@ -29,9 +29,7 @@ class StocksApp extends StatefulWidget {
 }
 
 class StocksAppState extends State<StocksApp> {
-
-  final Map<String, Stock> _stocks = <String, Stock>{};
-  final List<String> _symbols = <String>[];
+  StockData stocks;
 
   StockConfiguration _configuration = new StockConfiguration(
     stockMode: StockMode.optimistic,
@@ -49,11 +47,7 @@ class StocksAppState extends State<StocksApp> {
   @override
   void initState() {
     super.initState();
-    new StockDataFetcher((StockData data) {
-      setState(() {
-        data.appendTo(_stocks, _symbols);
-      });
-    });
+    stocks = new StockData();
   }
 
   void configurationUpdater(StockConfiguration value) {
@@ -80,19 +74,28 @@ class StocksAppState extends State<StocksApp> {
   }
 
   Route<Null> _getRoute(RouteSettings settings) {
+    // Routes, by convention, are split on slashes, like filesystem paths.
     final List<String> path = settings.name.split('/');
+    // We only support paths that start with a slash, so bail if
+    // the first component is not empty:
     if (path[0] != '')
       return null;
-    if (path[1] == 'stock') {
-      if (path.length != 3)
+    // If the path is "/stock:..." then show a stock page for the
+    // specified stock symbol.
+    if (path[1].startsWith('stock:')) {
+      // We don't yet support subpages of a stock, so bail if there's
+      // any more path components.
+      if (path.length != 2)
         return null;
-      if (_stocks.containsKey(path[2])) {
-        return new MaterialPageRoute<Null>(
-          settings: settings,
-          builder: (BuildContext context) => new StockSymbolPage(stock: _stocks[path[2]])
-        );
-      }
+      // Extract the symbol part of "stock:..." and return a route
+      // for that symbol.
+      final String symbol = path[1].substring(6);
+      return new MaterialPageRoute<Null>(
+        settings: settings,
+        builder: (BuildContext context) => new StockSymbolPage(symbol: symbol, stocks: stocks),
+      );
     }
+    // The other paths we support are in the routes table.
     return null;
   }
 
@@ -120,7 +123,7 @@ class StocksAppState extends State<StocksApp> {
       showPerformanceOverlay: _configuration.showPerformanceOverlay,
       showSemanticsDebugger: _configuration.showSemanticsDebugger,
       routes: <String, WidgetBuilder>{
-         '/':         (BuildContext context) => new StockHome(_stocks, _symbols, _configuration, configurationUpdater),
+         '/':         (BuildContext context) => new StockHome(stocks, _configuration, configurationUpdater),
          '/settings': (BuildContext context) => new StockSettings(_configuration, configurationUpdater)
       },
       onGenerateRoute: _getRoute,

examples/stocks/lib/stock_data.dart

@@ -10,6 +10,7 @@
 import 'dart:convert';
 import 'dart:math' as math;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:http/http.dart' as http;
 
@@ -38,54 +39,64 @@ class Stock {
   }
 }
 
-class StockData {
-  StockData(this._data);
-
-  final List<List<String>> _data;
-
-  void appendTo(Map<String, Stock> stocks, List<String> symbols) {
-    for (List<String> fields in _data) {
-      final Stock stock = new Stock.fromFields(fields);
-      symbols.add(stock.symbol);
-      stocks[stock.symbol] = stock;
+class StockData extends ChangeNotifier {
+  StockData() {
+    if (actuallyFetchData) {
+      _httpClient = createHttpClient();
+      _fetchNextChunk();
     }
-    symbols.sort();
-  }
-}
-
-typedef void StockDataCallback(StockData data);
-const int _kChunkCount = 30;
-
-String _urlToFetch(int chunk) {
-  return 'https://domokit.github.io/examples/stocks/data/stock_data_$chunk.json';
-}
-
-class StockDataFetcher {
-  StockDataFetcher(this.callback) {
-    _httpClient = createHttpClient();
-    _fetchNextChunk();
   }
 
-  final StockDataCallback callback;
+  final List<String> _symbols = <String>[];
+  final Map<String, Stock> _stocks = <String, Stock>{};
+
+  Iterable<String> get allSymbols => _symbols;
+
+  Stock operator [](String symbol) => _stocks[symbol];
+
+  bool get loading => _httpClient != null;
+
+  void add(List<List<String>> data) {
+    for (List<String> fields in data) {
+      final Stock stock = new Stock.fromFields(fields);
+      _symbols.add(stock.symbol);
+      _stocks[stock.symbol] = stock;
+    }
+    _symbols.sort();
+    notifyListeners();
+  }
+
+  static const int _kChunkCount = 30;
+  int _nextChunk = 0;
+
+  String _urlToFetch(int chunk) {
+    return 'https://domokit.github.io/examples/stocks/data/stock_data_$chunk.json';
+  }
+
   http.Client _httpClient;
 
   static bool actuallyFetchData = true;
 
-  int _nextChunk = 0;
-
   void _fetchNextChunk() {
-    if (!actuallyFetchData)
-      return;
     _httpClient.get(_urlToFetch(_nextChunk++)).then<Null>((http.Response response) {
       final String json = response.body;
       if (json == null) {
-        print("Failed to load stock data chunk ${_nextChunk - 1}");
-        return null;
+        debugPrint('Failed to load stock data chunk ${_nextChunk - 1}');
+        _end();
+        return;
       }
       final JsonDecoder decoder = const JsonDecoder();
-      callback(new StockData(decoder.convert(json)));
-      if (_nextChunk < _kChunkCount)
+      add(decoder.convert(json));
+      if (_nextChunk < _kChunkCount) {
         _fetchNextChunk();
+      } else {
+        _end();
+      }
     });
   }
+
+  void _end() {
+    _httpClient?.close();
+    _httpClient = null;
+  }
 }

examples/stocks/lib/stock_home.dart

@@ -50,10 +50,9 @@ class _NotImplementedDialog extends StatelessWidget {
 }
 
 class StockHome extends StatefulWidget {
-  const StockHome(this.stocks, this.symbols, this.configuration, this.updater);
+  const StockHome(this.stocks, this.configuration, this.updater);
 
-  final Map<String, Stock> stocks;
-  final List<String> symbols;
+  final StockData stocks;
   final StockConfiguration configuration;
   final ValueChanged<StockConfiguration> updater;
 
@@ -62,10 +61,9 @@ class StockHome extends StatefulWidget {
 }
 
 class StockHomeState extends State<StockHome> {
-
   final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
-  bool _isSearching = false;
   final TextEditingController _searchQuery = new TextEditingController();
+  bool _isSearching = false;
   bool _autorefresh = false;
 
   void _handleSearchBegin() {
@@ -82,10 +80,6 @@ class StockHomeState extends State<StockHome> {
     });
   }
 
-  void _handleSearchEnd() {
-    Navigator.pop(context);
-  }
-
   void _handleStockModeChange(StockMode value) {
     if (widget.updater != null)
       widget.updater(widget.configuration.copyWith(stockMode: value));
@@ -233,8 +227,8 @@ class StockHomeState extends State<StockHome> {
     );
   }
 
-  Iterable<Stock> _getStockList(Iterable<String> symbols) {
-    return symbols.map((String symbol) => widget.stocks[symbol])
+  static Iterable<Stock> _getStockList(StockData stocks, Iterable<String> symbols) {
+    return symbols.map<Stock>((String symbol) => stocks[symbol])
         .where((Stock stock) => stock != null);
   }
 
@@ -266,7 +260,7 @@ class StockHomeState extends State<StockHome> {
       stocks: stocks.toList(),
       onAction: _buyStock,
       onOpen: (Stock stock) {
-        Navigator.pushNamed(context, '/stock/${stock.symbol}');
+        Navigator.pushNamed(context, '/stock:${stock.symbol}');
       },
       onShow: (Stock stock) {
         _scaffoldKey.currentState.showBottomSheet<Null>((BuildContext context) => new StockSymbolBottomSheet(stock: stock));
@@ -275,22 +269,21 @@ class StockHomeState extends State<StockHome> {
   }
 
   Widget _buildStockTab(BuildContext context, StockHomeTab tab, List<String> stockSymbols) {
-    return new Container(
+    return new AnimatedBuilder(
       key: new ValueKey<StockHomeTab>(tab),
-      child: _buildStockList(context, _filterBySearchQuery(_getStockList(stockSymbols)).toList(), tab),
+      animation: new Listenable.merge(<Listenable>[_searchQuery, widget.stocks]),
+      builder: (BuildContext context, Widget child) {
+        return _buildStockList(context, _filterBySearchQuery(_getStockList(widget.stocks, stockSymbols)).toList(), tab);
+      },
     );
   }
 
   static const List<String> portfolioSymbols = const <String>["AAPL","FIZZ", "FIVE", "FLAT", "ZINC", "ZNGA"];
 
-  // TODO(abarth): Should we factor this into a SearchBar in the framework?
   Widget buildSearchBar() {
     return new AppBar(
-      leading: new IconButton(
-        icon: const Icon(Icons.arrow_back),
+      leading: new BackButton(
         color: Theme.of(context).accentColor,
-        onPressed: _handleSearchEnd,
-        tooltip: 'Back',
       ),
       title: new TextField(
         controller: _searchQuery,
@@ -330,7 +323,7 @@ class StockHomeState extends State<StockHome> {
         drawer: _buildDrawer(context),
         body: new TabBarView(
           children: <Widget>[
-            _buildStockTab(context, StockHomeTab.market, widget.symbols),
+            _buildStockTab(context, StockHomeTab.market, widget.stocks.allSymbols),
             _buildStockTab(context, StockHomeTab.portfolio, portfolioSymbols),
           ],
         ),
@@ -342,7 +335,6 @@ class StockHomeState extends State<StockHome> {
 class _CreateCompanySheet extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
-    // TODO(ianh): Fill this out.
     return new Column(
       children: <Widget>[
         const TextField(
@@ -351,6 +343,9 @@ class _CreateCompanySheet extends StatelessWidget {
             hintText: 'Company Name',
           ),
         ),
+        const Text('(This demo is not yet complete.)'),
+        // For example, we could add a button that actually updates the list
+        // and then contacts the server, etc.
       ],
     );
   }

examples/stocks/lib/stock_symbol_viewer.dart

@@ -15,6 +15,7 @@ class _StockSymbolView extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    assert(stock != null);
     final String lastSale = "\$${stock.lastSale.toStringAsFixed(2)}";
     String changeInPrice = "${stock.percentChange.toStringAsFixed(2)}%";
     if (stock.percentChange > 0)
@@ -63,30 +64,49 @@ class _StockSymbolView extends StatelessWidget {
 }
 
 class StockSymbolPage extends StatelessWidget {
-  const StockSymbolPage({ this.stock });
+  const StockSymbolPage({ this.symbol, this.stocks });
 
-  final Stock stock;
+  final String symbol;
+  final StockData stocks;
 
   @override
   Widget build(BuildContext context) {
-    return new Scaffold(
-      appBar: new AppBar(
-        title: new Text(stock.name)
-      ),
-      body: new SingleChildScrollView(
-        child: new Container(
-          margin: const EdgeInsets.all(20.0),
-          child: new Card(
-            child: new _StockSymbolView(
-              stock: stock,
-              arrow: new Hero(
-                tag: stock,
-                child: new StockArrow(percentChange: stock.percentChange)
+    return new AnimatedBuilder(
+      animation: stocks,
+      builder: (BuildContext context, Widget child) {
+        final Stock stock = stocks[symbol];
+        return new Scaffold(
+          appBar: new AppBar(
+            title: new Text(stock?.name ?? symbol)
+          ),
+          body: new SingleChildScrollView(
+            child: new Container(
+              margin: const EdgeInsets.all(20.0),
+              child: new Card(
+                child: new AnimatedCrossFade(
+                  duration: const Duration(milliseconds: 300),
+                  firstChild: const Padding(
+                    padding: const EdgeInsets.all(20.0),
+                    child: const Center(child: const CircularProgressIndicator()),
+                  ),
+                  secondChild: stock != null
+                    ? new _StockSymbolView(
+                      stock: stock,
+                      arrow: new Hero(
+                        tag: stock,
+                        child: new StockArrow(percentChange: stock.percentChange),
+                      ),
+                    ) : new Padding(
+                        padding: const EdgeInsets.all(20.0),
+                        child: new Center(child: new Text('$symbol not found')),
+                    ),
+                  crossFadeState: stock == null && stocks.loading ? CrossFadeState.showFirst : CrossFadeState.showSecond,
+                ),
               )
             )
           )
-        )
-      )
+        );
+      },
     );
   }
 }

examples/stocks/test/icon_color_test.dart

@@ -46,9 +46,9 @@ void checkIconColor(WidgetTester tester, String label, Color color) {
 }
 
 void main() {
-  stock_data.StockDataFetcher.actuallyFetchData = false;
+  stock_data.StockData.actuallyFetchData = false;
 
-  testWidgets("Test icon colors", (WidgetTester tester) async {
+  testWidgets('Icon colors', (WidgetTester tester) async {
     stocks.main(); // builds the app and schedules a frame but doesn't trigger one
     await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
     await tester.pump(); // triggers a frame

examples/stocks/test/locale_test.dart

@@ -7,14 +7,14 @@ import 'package:stocks/main.dart' as stocks;
 import 'package:stocks/stock_data.dart' as stock_data;
 
 void main() {
-  stock_data.StockDataFetcher.actuallyFetchData = false;
+  stock_data.StockData.actuallyFetchData = false;
 
-  testWidgets("Test changing locale", (WidgetTester tester) async {
+  testWidgets('Changing locale', (WidgetTester tester) async {
     stocks.main();
     await tester.idle(); // see https://github.com/flutter/flutter/issues/1865
     await tester.pump();
     expect(find.text('MARKET'), findsOneWidget);
-    await tester.binding.setLocale("es", "US");
+    await tester.binding.setLocale('es', 'US');
     await tester.idle();
     await tester.pump();
     expect(find.text('MERCADO'), findsOneWidget);

examples/stocks/test/search_test.dart

@@ -0,0 +1,53 @@
+// Copyright 2016 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 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:stocks/main.dart' as stocks;
+import 'package:stocks/stock_data.dart' as stock_data;
+
+void main() {
+  stock_data.StockData.actuallyFetchData = false;
+
+  testWidgets('Search', (WidgetTester tester) async {
+    stocks.main(); // builds the app and schedules a frame but doesn't trigger one
+    await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
+    await tester.pump(); // triggers a frame
+
+    expect(find.text('AAPL'), findsNothing);
+    expect(find.text('BANA'), findsNothing);
+
+    final stocks.StocksAppState app = tester.state<stocks.StocksAppState>(find.byType(stocks.StocksApp));
+    app.stocks.add(<List<String>>[
+      // "Symbol","Name","LastSale","MarketCap","IPOyear","Sector","industry","Summary Quote"
+      <String>['AAPL', 'Apple', '', '', '', '', '', ''],
+      <String>['BANA', 'Banana', '', '', '', '', '', ''],
+    ]);
+    await tester.pump();
+
+    expect(find.text('AAPL'), findsOneWidget);
+    expect(find.text('BANA'), findsOneWidget);
+
+    await tester.tap(find.byTooltip('Search'));
+    // We skip a minute at a time so that each phase of the animation
+    // is done in two frames, the start frame and the end frame.
+    // There are two phases currently, so that results in three frames.
+    expect(await tester.pumpAndSettle(const Duration(minutes: 1)), 3);
+
+    expect(find.text('AAPL'), findsOneWidget);
+    expect(find.text('BANA'), findsOneWidget);
+
+    await tester.enterText(find.byType(EditableText), 'B');
+    await tester.pump();
+
+    expect(find.text('AAPL'), findsNothing);
+    expect(find.text('BANA'), findsOneWidget);
+
+    await tester.enterText(find.byType(EditableText), 'X');
+    await tester.pump();
+
+    expect(find.text('AAPL'), findsNothing);
+    expect(find.text('BANA'), findsNothing);
+  });
+}

packages/flutter/lib/src/material/app.dart

@@ -26,10 +26,29 @@ const TextStyle _errorTextStyle = const TextStyle(
 /// An application that uses material design.
 ///
 /// A convenience widget that wraps a number of widgets that are commonly
-/// required for material design applications. It builds upon a
-/// [WidgetsApp] by adding material-design specific functionality, such as
-/// [AnimatedTheme] and [GridPaper]. This widget also configures the top-level
-/// [Navigator]'s observer to perform [Hero] animations.
+/// required for material design applications. It builds upon a [WidgetsApp] by
+/// adding material-design specific functionality, such as [AnimatedTheme] and
+/// [GridPaper].
+///
+/// The [MaterialApp] configures the top-level [Navigator] to search for routes
+/// in the following order:
+///
+///  1. For the `/` route, the [home] property, if non-null, is used.
+///
+///  2. Otherwise, the [routes] table is used, if it has an entry for the route.
+///
+///  3. Otherwise, [onGenerateRoute] is called, if provided. It should return a
+///     non-null value for any _valid_ route not handled by [home] and [routes].
+///
+///  4. Finally if all else fails [onUnknownRoute] is called.
+///
+/// At least one of these options must handle the `/` route, since it is used
+/// when an invalid [initialRoute] is specified on startup (e.g. by another
+/// application launching this one with an intent on Android; see
+/// [Window.defaultRouteName]).
+///
+/// This widget also configures the top-level [Navigator]'s observer to perform
+/// [Hero] animations.
 ///
 /// See also:
 ///
@@ -38,24 +57,27 @@ const TextStyle _errorTextStyle = const TextStyle(
 ///  * [MaterialPageRoute], which defines an app page that transitions in a material-specific way.
 ///  * [WidgetsApp], which defines the basic app elements but does not depend on the material library.
 class MaterialApp extends StatefulWidget {
-
   /// Creates a MaterialApp.
   ///
-  /// At least one of [home], [routes], or [onGenerateRoute] must be
-  /// given. If only [routes] is given, it must include an entry for the
-  /// [initialRoute], which defaults to [Navigator.defaultRouteName]
-  /// (`'/'`).
+  /// At least one of [home], [routes], or [onGenerateRoute] must be given. If
+  /// only [routes] is given, it must include an entry for the
+  /// [Navigator.defaultRouteName] (`/`), since that is the route used when the
+  /// application is launched with an intent that specifies an otherwise
+  /// unsupported route.
   ///
   /// This class creates an instance of [WidgetsApp].
-  MaterialApp({
+  ///
+  /// The boolean arguments, [routes], and [navigatorObservers], must not be null.
+  MaterialApp({ // can't be const because the asserts use methods on Map :-(
     Key key,
     this.title,
     this.color,
     this.theme,
     this.home,
     this.routes: const <String, WidgetBuilder>{},
-    this.initialRoute: Navigator.defaultRouteName,
+    this.initialRoute,
     this.onGenerateRoute,
+    this.onUnknownRoute,
     this.onLocaleChanged,
     this.navigatorObservers: const <NavigatorObserver>[],
     this.debugShowMaterialGrid: false,
@@ -64,10 +86,32 @@ class MaterialApp extends StatefulWidget {
     this.checkerboardOffscreenLayers: false,
     this.showSemanticsDebugger: false,
     this.debugShowCheckedModeBanner: true
-  }) : assert(debugShowMaterialGrid != null),
-       assert(routes != null),
-       assert(!routes.containsKey(initialRoute) || (home == null)),
-       assert(routes.containsKey(initialRoute) || (home != null) || (onGenerateRoute != null)),
+  }) : assert(routes != null),
+       assert(navigatorObservers != null),
+       assert(debugShowMaterialGrid != null),
+       assert(showPerformanceOverlay != null),
+       assert(checkerboardRasterCacheImages != null),
+       assert(checkerboardOffscreenLayers != null),
+       assert(showSemanticsDebugger != null),
+       assert(debugShowCheckedModeBanner != null),
+       assert(
+         home == null ||
+         !routes.containsKey(Navigator.defaultRouteName),
+         'If the home property is specified, the routes table '
+         'cannot include an entry for "/", since it would be redundant.'
+       ),
+       assert(
+         home != null ||
+         routes.containsKey(Navigator.defaultRouteName) ||
+         onGenerateRoute != null ||
+         onUnknownRoute != null,
+         'Either the home property must be specified, '
+         'or the routes table must include an entry for "/", '
+         'or there must be on onGenerateRoute callback specified, '
+         'or there must be an onUnknownRoute callback specified, '
+         'because otherwise there is nothing to fall back on if the '
+         'app is started with an intent that specifies an unknown route.'
+       ),
        super(key: key);
 
   /// A one-line description of this app for use in the window manager.
@@ -76,20 +120,20 @@ class MaterialApp extends StatefulWidget {
   /// The colors to use for the application's widgets.
   final ThemeData theme;
 
-  /// The widget for the default route of the app
-  /// ([Navigator.defaultRouteName], which is `'/'`).
+  /// The widget for the default route of the app ([Navigator.defaultRouteName],
+  /// which is `/`).
   ///
-  /// This is the page that is displayed first when the application is
-  /// started normally.
+  /// This is the route that is displayed first when the application is started
+  /// normally, unless [initialRoute] is specified. It's also the route that's
+  /// displayed if the [initialRoute] can't be displayed.
   ///
   /// To be able to directly call [Theme.of], [MediaQuery.of],
   /// [LocaleQuery.of], etc, in the code sets the [home] argument in
   /// the constructor, you can use a [Builder] widget to get a
   /// [BuildContext].
   ///
-  /// If this is not specified, then either the route with name `'/'`
-  /// must be given in [routes], or the [onGenerateRoute] callback
-  /// must be able to build a widget for that route.
+  /// If [home] is specified, then [routes] must not include an entry for `/`,
+  /// as [home] takes its place.
   final Widget home;
 
   /// The primary color to use for the application in the operating system
@@ -108,29 +152,71 @@ class MaterialApp extends StatefulWidget {
   ///
   /// If the app only has one page, then you can specify it using [home] instead.
   ///
-  /// If [home] is specified, then it is an error to provide a route
-  /// in this map for the [Navigator.defaultRouteName] route (`'/'`).
+  /// If [home] is specified, then it implies an entry in this table for the
+  /// [Navigator.defaultRouteName] route (`/`), and it is an error to
+  /// redundantly provide such a route in the [routes] table.
   ///
-  /// If a route is requested that is not specified in this table (or
-  /// by [home]), then the [onGenerateRoute] callback is called to
-  /// build the page instead.
+  /// If a route is requested that is not specified in this table (or by
+  /// [home]), then the [onGenerateRoute] callback is called to build the page
+  /// instead.
   final Map<String, WidgetBuilder> routes;
 
   /// The name of the first route to show.
   ///
-  /// Defaults to [Window.defaultRouteName].
+  /// Defaults to [Window.defaultRouteName], which may be overridden by the code
+  /// that launched the application.
+  ///
+  /// If the route contains slashes, then it is treated as a "deep link", and
+  /// before this route is pushed, the routes leading to this one are pushed
+  /// also. For example, if the route was `/a/b/c`, then the app would start
+  /// with the three routes `/a`, `/a/b`, and `/a/b/c` loaded, in that order.
+  ///
+  /// If any part of this process fails to generate routes, then the
+  /// [initialRoute] is ignored and [Navigator.defaultRouteName] is used instead
+  /// (`/`). This can happen if the app is started with an intent that specifies
+  /// a non-existent route.
+  ///
+  /// See also:
+  ///
+  ///  * [Navigator.initialRoute], which is used to implement this property.
+  ///  * [Navigator.push], for pushing additional routes.
+  ///  * [Navigator.pop], for removing a route from the stack.
   final String initialRoute;
 
   /// The route generator callback used when the app is navigated to a
   /// named route.
+  ///
+  /// This is used if [routes] does not contain the requested route.
+  ///
+  /// If this returns null when building the routes to handle the specified
+  /// [initialRoute], then all the routes are discarded and
+  /// [Navigator.defaultRouteName] is used instead (`/`). See [initialRoute].
+  ///
+  /// During normal app operation, the [onGenerateRoute] callback will only be
+  /// applied to route names pushed by the application, and so should never
+  /// return null.
   final RouteFactory onGenerateRoute;
 
+  /// Called when [onGenerateRoute] fails to generate a route, except for the
+  /// [initialRoute].
+  ///
+  /// This callback is typically used for error handling. For example, this
+  /// callback might always generate a "not found" page that describes the route
+  /// that wasn't found.
+  ///
+  /// The default implementation pushes a route that displays an ugly error
+  /// message.
+  final RouteFactory onUnknownRoute;
+
   /// Callback that is called when the operating system changes the
   /// current locale.
   final LocaleChangedCallback onLocaleChanged;
 
   /// Turns on a performance overlay.
-  /// https://flutter.io/debugging/#performanceoverlay
+  ///
+  /// See also:
+  ///
+  ///  * <https://flutter.io/debugging/#performanceoverlay>
   final bool showPerformanceOverlay;
 
   /// Turns on checkerboarding of raster cache images.
@@ -162,9 +248,13 @@ class MaterialApp extends StatefulWidget {
   final List<NavigatorObserver> navigatorObservers;
 
   /// Turns on a [GridPaper] overlay that paints a baseline grid
-  /// Material apps:
-  /// https://material.google.com/layout/metrics-keylines.html
+  /// Material apps.
+  ///
   /// Only available in checked mode.
+  ///
+  /// See also:
+  ///
+  ///  * <https://material.google.com/layout/metrics-keylines.html>
   final bool debugShowMaterialGrid;
 
   @override
@@ -210,13 +300,16 @@ class _MaterialAppState extends State<MaterialApp> {
   }
 
   Route<dynamic> _onGenerateRoute(RouteSettings settings) {
-    WidgetBuilder builder = widget.routes[settings.name];
-    if (builder == null && widget.home != null && settings.name == Navigator.defaultRouteName)
+    final String name = settings.name;
+    WidgetBuilder builder;
+    if (name == Navigator.defaultRouteName && widget.home != null)
       builder = (BuildContext context) => widget.home;
+    else
+      builder = widget.routes[name];
     if (builder != null) {
       return new MaterialPageRoute<Null>(
         builder: builder,
-        settings: settings
+        settings: settings,
       );
     }
     if (widget.onGenerateRoute != null)
@@ -224,6 +317,38 @@ class _MaterialAppState extends State<MaterialApp> {
     return null;
   }
 
+  Route<dynamic> _onUnknownRoute(RouteSettings settings) {
+    assert(() {
+      if (widget.onUnknownRoute == null) {
+        throw new FlutterError(
+          'Could not find a generator for route $settings in the $runtimeType.\n'
+          'Generators for routes are searched for in the following order:\n'
+          ' 1. For the "/" route, the "home" property, if non-null, is used.\n'
+          ' 2. Otherwise, the "routes" table is used, if it has an entry for '
+          'the route.\n'
+          ' 3. Otherwise, onGenerateRoute is called. It should return a '
+          'non-null value for any valid route not handled by "home" and "routes".\n'
+          ' 4. Finally if all else fails onUnknownRoute is called.\n'
+          'Unfortunately, onUnknownRoute was not set.'
+        );
+      }
+      return true;
+    });
+    final Route<dynamic> result = widget.onUnknownRoute(settings);
+    assert(() {
+      if (result == null) {
+        throw new FlutterError(
+          'The onUnknownRoute callback returned null.\n'
+          'When the $runtimeType requested the route $settings from its '
+          'onUnknownRoute callback, the callback returned null. Such callbacks '
+          'must never return null.'
+        );
+      }
+      return true;
+    });
+    return result;
+  }
+
   @override
   Widget build(BuildContext context) {
     final ThemeData theme = widget.theme ?? new ThemeData.fallback();
@@ -241,6 +366,7 @@ class _MaterialAppState extends State<MaterialApp> {
               ..add(_heroController),
         initialRoute: widget.initialRoute,
         onGenerateRoute: _onGenerateRoute,
+        onUnknownRoute: _onUnknownRoute,
         onLocaleChanged: widget.onLocaleChanged,
         showPerformanceOverlay: widget.showPerformanceOverlay,
         checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,

packages/flutter/lib/src/material/back_button.dart

@@ -69,12 +69,19 @@ class BackButtonIcon extends StatelessWidget {
 class BackButton extends StatelessWidget {
   /// Creates an [IconButton] with the appropriate "back" icon for the current
   /// target platform.
-  const BackButton({ Key key }) : super(key: key);
+  const BackButton({ Key key, this.color }) : super(key: key);
+
+  /// The color to use for the icon.
+  ///
+  /// Defaults to the [IconThemeData.color] specified in the ambient [IconTheme],
+  /// which usually matches the ambient [Theme]'s [ThemeData.iconTheme].
+  final Color color;
 
   @override
   Widget build(BuildContext context) {
     return new IconButton(
       icon: const BackButtonIcon(),
+      color: color,
       tooltip: 'Back', // TODO(ianh): Figure out how to localize this string
       onPressed: () {
         Navigator.of(context).maybePop();

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

@@ -93,7 +93,7 @@ class RenderErrorBox extends RenderBox {
 
   /// The paragraph style to use when painting [RenderErrorBox] objects.
   static ui.ParagraphStyle paragraphStyle = new ui.ParagraphStyle(
-    lineHeight: 0.85
+    lineHeight: 1.0,
   );
 
   @override

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

@@ -38,9 +38,13 @@ typedef Future<LocaleQueryData> LocaleChangedCallback(Locale locale);
 class WidgetsApp extends StatefulWidget {
   /// Creates a widget that wraps a number of widgets that are commonly
   /// required for an application.
+  ///
+  /// The boolean arguments, [color], [navigatorObservers], and
+  /// [onGenerateRoute] must not be null.
   const WidgetsApp({
     Key key,
     @required this.onGenerateRoute,
+    this.onUnknownRoute,
     this.title,
     this.textStyle,
     @required this.color,
@@ -52,12 +56,14 @@ class WidgetsApp extends StatefulWidget {
     this.checkerboardOffscreenLayers: false,
     this.showSemanticsDebugger: false,
     this.debugShowCheckedModeBanner: true
-  }) : assert(color != null),
-       assert(onGenerateRoute != null),
+  }) : assert(onGenerateRoute != null),
+       assert(color != null),
+       assert(navigatorObservers != null),
        assert(showPerformanceOverlay != null),
        assert(checkerboardRasterCacheImages != null),
        assert(checkerboardOffscreenLayers != null),
        assert(showSemanticsDebugger != null),
+       assert(debugShowCheckedModeBanner != null),
        super(key: key);
 
   /// A one-line description of this app for use in the window manager.
@@ -75,11 +81,46 @@ class WidgetsApp extends StatefulWidget {
 
   /// The route generator callback used when the app is navigated to a
   /// named route.
+  ///
+  /// If this returns null when building the routes to handle the specified
+  /// [initialRoute], then all the routes are discarded and
+  /// [Navigator.defaultRouteName] is used instead (`/`). See [initialRoute].
+  ///
+  /// During normal app operation, the [onGenerateRoute] callback will only be
+  /// applied to route names pushed by the application, and so should never
+  /// return null.
   final RouteFactory onGenerateRoute;
 
+  /// Called when [onGenerateRoute] fails to generate a route.
+  ///
+  /// This callback is typically used for error handling. For example, this
+  /// callback might always generate a "not found" page that describes the route
+  /// that wasn't found.
+  ///
+  /// Unknown routes can arise either from errors in the app or from external
+  /// requests to push routes, such as from Android intents.
+  final RouteFactory onUnknownRoute;
+
   /// The name of the first route to show.
   ///
-  /// Defaults to [Window.defaultRouteName].
+  /// Defaults to [Window.defaultRouteName], which may be overridden by the code
+  /// that launched the application.
+  ///
+  /// If the route contains slashes, then it is treated as a "deep link", and
+  /// before this route is pushed, the routes leading to this one are pushed
+  /// also. For example, if the route was `/a/b/c`, then the app would start
+  /// with the three routes `/a`, `/a/b`, and `/a/b/c` loaded, in that order.
+  ///
+  /// If any part of this process fails to generate routes, then the
+  /// [initialRoute] is ignored and [Navigator.defaultRouteName] is used instead
+  /// (`/`). This can happen if the app is started with an intent that specifies
+  /// a non-existent route.
+  ///
+  /// See also:
+  ///
+  ///  * [Navigator.initialRoute], which is used to implement this property.
+  ///  * [Navigator.push], for pushing additional routes.
+  ///  * [Navigator.pop], for removing a route from the stack.
   final String initialRoute;
 
   /// Callback that is called when the operating system changes the
@@ -221,6 +262,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
             key: _navigator,
             initialRoute: widget.initialRoute ?? ui.window.defaultRouteName,
             onGenerateRoute: widget.onGenerateRoute,
+            onUnknownRoute: widget.onUnknownRoute,
             observers: widget.navigatorObservers
           )
         )
@@ -238,13 +280,13 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
     // options are set.
     if (widget.showPerformanceOverlay || WidgetsApp.showPerformanceOverlayOverride) {
       performanceOverlay = new PerformanceOverlay.allEnabled(
-          checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
-          checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
+        checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
+        checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
       );
     } else if (widget.checkerboardRasterCacheImages || widget.checkerboardOffscreenLayers) {
       performanceOverlay = new PerformanceOverlay(
-          checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
-          checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
+        checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
+        checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
       );
     }
 

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

@@ -12,7 +12,11 @@ import 'debug.dart';
 import 'framework.dart';
 
 export 'package:flutter/animation.dart';
-export 'package:flutter/foundation.dart' show TargetPlatform;
+export 'package:flutter/foundation.dart' show
+  ChangeNotifier,
+  Listenable,
+  TargetPlatform,
+  ValueNotifier;
 export 'package:flutter/painting.dart';
 export 'package:flutter/rendering.dart' show
   Axis,

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

@@ -207,6 +207,18 @@ class RouteSettings {
     this.isInitialRoute: false,
   });
 
+  /// Creates a copy of this route settings object with the given fields
+  /// replaced with the new values.
+  RouteSettings copyWith({
+    String name,
+    bool isInitialRoute,
+  }) {
+    return new RouteSettings(
+      name: name ?? this.name,
+      isInitialRoute: isInitialRoute ?? this.isInitialRoute,
+    );
+  }
+
   /// The name of the route (e.g., "/settings").
   ///
   /// If null, the route is anonymous.
@@ -374,7 +386,7 @@ typedef bool RoutePredicate(Route<dynamic> route);
 /// The app's home page route is named '/' by default.
 ///
 /// The [MaterialApp] can be created
-/// with a `Map<String, WidgetBuilder>` which maps from a route's name to
+/// with a [Map<String, WidgetBuilder>] which maps from a route's name to
 /// a builder function that will create it. The [MaterialApp] uses this
 /// map to create a value for its navigator's [onGenerateRoute] callback.
 ///
@@ -496,6 +508,17 @@ class Navigator extends StatefulWidget {
        super(key: key);
 
   /// The name of the first route to show.
+  ///
+  /// By default, this defers to [dart:ui.Window.defaultRouteName].
+  ///
+  /// If this string contains any `/` characters, then the string is split on
+  /// those characters and substrings from the start of the string up to each
+  /// such character are, in turn, used as routes to push.
+  ///
+  /// For example, if the route `/stocks/HOOLI` was used as the [initialRoute],
+  /// then the [Navigator] would push the following routes on startup: `/`,
+  /// `/stocks`, `/stocks/HOOLI`. This enables deep linking while allowing the
+  /// application to maintain a predictable route history.
   final String initialRoute;
 
   /// Called to generate a route for a given [RouteSettings].
@@ -514,7 +537,12 @@ class Navigator extends StatefulWidget {
   /// A list of observers for this navigator.
   final List<NavigatorObserver> observers;
 
-  /// The default name for the initial route.
+  /// The default name for the [initialRoute].
+  ///
+  /// See also:
+  ///
+  ///  * [dart:ui.Window.defaultRouteName], which reflects the route that the
+  ///    application was started with.
   static const String defaultRouteName = '/';
 
   /// Push a named route onto the navigator that most tightly encloses the given context.
@@ -730,6 +758,8 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   /// The [FocusScopeNode] for the [FocusScope] that encloses the routes.
   final FocusScopeNode focusScopeNode = new FocusScopeNode();
 
+  final List<OverlayEntry> _initialOverlayEntries = <OverlayEntry>[];
+
   @override
   void initState() {
     super.initState();
@@ -737,10 +767,57 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
       assert(observer.navigator == null);
       observer._navigator = this;
     }
-    push(widget.onGenerateRoute(new RouteSettings(
-      name: widget.initialRoute ?? Navigator.defaultRouteName,
-      isInitialRoute: true
-    )));
+    String initialRouteName = widget.initialRoute ?? Navigator.defaultRouteName;
+    if (initialRouteName.startsWith('/') && initialRouteName.length > 1) {
+      initialRouteName = initialRouteName.substring(1); // strip leading '/'
+      assert(Navigator.defaultRouteName == '/');
+      final List<String> plannedInitialRouteNames = <String>[
+        Navigator.defaultRouteName,
+      ];
+      final List<Route<dynamic>> plannedInitialRoutes = <Route<dynamic>>[
+        _routeNamed(Navigator.defaultRouteName, allowNull: true),
+      ];
+      final List<String> routeParts = initialRouteName.split('/');
+      if (initialRouteName.isNotEmpty) {
+        String routeName = '';
+        for (String part in routeParts) {
+          routeName += '/$part';
+          plannedInitialRouteNames.add(routeName);
+          plannedInitialRoutes.add(_routeNamed(routeName, allowNull: true));
+        }
+      }
+      if (plannedInitialRoutes.contains(null)) {
+        assert(() {
+          FlutterError.reportError(
+            new FlutterErrorDetails( // ignore: prefer_const_constructors, https://github.com/dart-lang/sdk/issues/29952
+              exception:
+                'Could not navigate to initial route.\n'
+                'The requested route name was: "/$initialRouteName"\n'
+                'The following routes were therefore attempted:\n'
+                ' * ${plannedInitialRouteNames.join("\n * ")}\n'
+                'This resulted in the following objects:\n'
+                ' * ${plannedInitialRoutes.join("\n * ")}\n'
+                'One or more of those objects was null, and therefore the initial route specified will be '
+                'ignored and "${Navigator.defaultRouteName}" will be used instead.'
+            ),
+          );
+          return true;
+        });
+        push(_routeNamed(Navigator.defaultRouteName));
+      } else {
+        for (Route<dynamic> route in plannedInitialRoutes)
+          push(route);
+      }
+    } else {
+      Route<dynamic> route;
+      if (initialRouteName != Navigator.defaultRouteName)
+        route = _routeNamed(initialRouteName, allowNull: true);
+      if (route == null)
+        route = _routeNamed(Navigator.defaultRouteName);
+      push(route);
+    }
+    for (Route<dynamic> route in _history)
+      _initialOverlayEntries.addAll(route.overlayEntries);
   }
 
   @override
@@ -785,15 +862,40 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
 
   bool _debugLocked = false; // used to prevent re-entrant calls to push, pop, and friends
 
-  Route<dynamic> _routeNamed(String name) {
+  Route<dynamic> _routeNamed(String name, { bool allowNull: false }) {
     assert(!_debugLocked);
     assert(name != null);
-    final RouteSettings settings = new RouteSettings(name: name);
+    final RouteSettings settings = new RouteSettings(
+      name: name,
+      isInitialRoute: _history.isEmpty,
+    );
     Route<dynamic> route = widget.onGenerateRoute(settings);
-    if (route == null) {
-      assert(widget.onUnknownRoute != null);
+    if (route == null && !allowNull) {
+      assert(() {
+        if (widget.onUnknownRoute == null) {
+          throw new FlutterError(
+            'If a Navigator has no onUnknownRoute, then its onGenerateRoute must never return null.\n'
+            'When trying to build the route "$name", onGenerateRoute returned null, but there was no '
+            'onUnknownRoute callback specified.\n'
+            'The Navigator was:\n'
+            '  $this'
+          );
+        }
+        return true;
+      });
       route = widget.onUnknownRoute(settings);
-      assert(route != null);
+      assert(() {
+        if (route == null) {
+          throw new FlutterError(
+            'A Navigator\'s onUnknownRoute returned null.\n'
+            'When trying to build the route "$name", both onGenerateRoute and onUnknownRoute returned '
+            'null. The onUnknownRoute callback should never return null.\n'
+            'The Navigator was:\n'
+            '  $this'
+          );
+        }
+        return true;
+      });
     }
     return route;
   }
@@ -1245,7 +1347,6 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   Widget build(BuildContext context) {
     assert(!_debugLocked);
     assert(_history.isNotEmpty);
-    final Route<dynamic> initialRoute = _history.first;
     return new Listener(
       onPointerDown: _handlePointerDown,
       onPointerUp: _handlePointerUpOrCancel,
@@ -1257,7 +1358,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
           autofocus: true,
           child: new Overlay(
             key: _overlayKey,
-            initialEntries: initialRoute.overlayEntries,
+            initialEntries: _initialOverlayEntries,
           ),
         ),
       ),

packages/flutter/test/material/app_test.dart

@@ -152,34 +152,65 @@ void main() {
     expect(find.text('route "/"'), findsOneWidget);
   });
 
-  testWidgets('Custom initialRoute only', (WidgetTester tester) async {
+  testWidgets('One-step initial route', (WidgetTester tester) async {
     await tester.pumpWidget(
       new MaterialApp(
         initialRoute: '/a',
         routes: <String, WidgetBuilder>{
+          '/': (BuildContext context) => const Text('route "/"'),
           '/a': (BuildContext context) => const Text('route "/a"'),
+          '/a/b': (BuildContext context) => const Text('route "/a/b"'),
+          '/b': (BuildContext context) => const Text('route "/b"'),
         },
       )
     );
 
+    expect(find.text('route "/"'), findsOneWidget);
     expect(find.text('route "/a"'), findsOneWidget);
+    expect(find.text('route "/a/b"'), findsNothing);
+    expect(find.text('route "/b"'), findsNothing);
   });
 
-  testWidgets('Custom initialRoute along with Navigator.defaultRouteName', (WidgetTester tester) async {
+  testWidgets('Two-step initial route', (WidgetTester tester) async {
     final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
       '/': (BuildContext context) => const Text('route "/"'),
       '/a': (BuildContext context) => const Text('route "/a"'),
+      '/a/b': (BuildContext context) => const Text('route "/a/b"'),
       '/b': (BuildContext context) => const Text('route "/b"'),
     };
 
     await tester.pumpWidget(
       new MaterialApp(
-        initialRoute: '/a',
+        initialRoute: '/a/b',
         routes: routes,
       )
     );
-    expect(find.text('route "/"'), findsNothing);
+    expect(find.text('route "/"'), findsOneWidget);
     expect(find.text('route "/a"'), findsOneWidget);
+    expect(find.text('route "/a/b"'), findsOneWidget);
+    expect(find.text('route "/b"'), findsNothing);
+  });
+
+  testWidgets('Initial route with missing step', (WidgetTester tester) async {
+    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
+      '/': (BuildContext context) => const Text('route "/"'),
+      '/a': (BuildContext context) => const Text('route "/a"'),
+      '/a/b': (BuildContext context) => const Text('route "/a/b"'),
+      '/b': (BuildContext context) => const Text('route "/b"'),
+    };
+
+    await tester.pumpWidget(
+      new MaterialApp(
+        initialRoute: '/a/b/c',
+        routes: routes,
+      )
+    );
+    final dynamic exception = tester.takeException();
+    expect(exception is String, isTrue);
+    expect(exception.startsWith('Could not navigate to initial route.'), isTrue);
+    expect(find.text('route "/"'), findsOneWidget);
+    expect(find.text('route "/a"'), findsNothing);
+    expect(find.text('route "/a/b"'), findsNothing);
     expect(find.text('route "/b"'), findsNothing);
   });
 
@@ -196,23 +227,41 @@ void main() {
         routes: routes,
       )
     );
-    expect(find.text('route "/"'), findsNothing);
+    expect(find.text('route "/"'), findsOneWidget);
     expect(find.text('route "/a"'), findsOneWidget);
     expect(find.text('route "/b"'), findsNothing);
 
+    // changing initialRoute has no effect
     await tester.pumpWidget(
       new MaterialApp(
         initialRoute: '/b',
         routes: routes,
       )
     );
-    expect(find.text('route "/"'), findsNothing);
+    expect(find.text('route "/"'), findsOneWidget);
     expect(find.text('route "/a"'), findsOneWidget);
     expect(find.text('route "/b"'), findsNothing);
 
+    // removing it has no effect
     await tester.pumpWidget(new MaterialApp(routes: routes));
-    expect(find.text('route "/"'), findsNothing);
+    expect(find.text('route "/"'), findsOneWidget);
     expect(find.text('route "/a"'), findsOneWidget);
     expect(find.text('route "/b"'), findsNothing);
   });
+
+  testWidgets('onGenerateRoute / onUnknownRoute', (WidgetTester tester) async {
+    final List<String> log = <String>[];
+    await tester.pumpWidget(
+      new MaterialApp(
+        onGenerateRoute: (RouteSettings settings) {
+          log.add('onGenerateRoute ${settings.name}');
+        },
+        onUnknownRoute: (RouteSettings settings) {
+          log.add('onUnknownRoute ${settings.name}');
+        },
+      )
+    );
+    expect(tester.takeException(), isFlutterError);
+    expect(log, <String>['onGenerateRoute /', 'onUnknownRoute /']);
+  });
 }

packages/flutter/test/widgets/routes_test.dart

@@ -98,6 +98,12 @@ void main() {
   testWidgets('Route settings', (WidgetTester tester) async {
     final RouteSettings settings = const RouteSettings(name: 'A');
     expect(settings, hasOneLineDescription);
+    final RouteSettings settings2 = settings.copyWith(name: 'B');
+    expect(settings2.name, 'B');
+    expect(settings2.isInitialRoute, false);
+    final RouteSettings settings3 = settings2.copyWith(isInitialRoute: true);
+    expect(settings3.name, 'B');
+    expect(settings3.isInitialRoute, true);
   });
 
   testWidgets('Route management - push, replace, pop', (WidgetTester tester) async {

packages/flutter_driver/lib/driver_extension.dart

@@ -24,4 +24,4 @@
 ///     }
 library flutter_driver_extension;
 
-export 'src/extension.dart' show enableFlutterDriverExtension;
+export 'src/extension.dart' show enableFlutterDriverExtension, DataHandler;

packages/flutter_driver/lib/src/driver.dart

@@ -21,6 +21,7 @@ import 'gesture.dart';
 import 'health.dart';
 import 'message.dart';
 import 'render_tree.dart';
+import 'request_data.dart';
 import 'semantics.dart';
 import 'timeline.dart';
 
@@ -384,6 +385,13 @@ class FlutterDriver {
     return GetTextResult.fromJson(await _sendCommand(new GetText(finder, timeout: timeout))).text;
   }
 
+  /// Sends a string and returns a string.
+  ///
+  /// The application can respond to this by providing a handler to [enableFlutterDriverExtension].
+  Future<String> requestData(String message, { Duration timeout }) async {
+    return RequestDataResult.fromJson(await _sendCommand(new RequestData(message, timeout: timeout))).message;
+  }
+
   /// Turns semantics on or off in the Flutter app under test.
   ///
   /// Returns `true` when the call actually changed the state from on to off or

packages/flutter_driver/lib/src/extension.dart

@@ -6,10 +6,12 @@ import 'dart:async';
 
 import 'package:meta/meta.dart';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart' show RendererBinding, SemanticsHandle;
 import 'package:flutter/scheduler.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -20,19 +22,26 @@ import 'gesture.dart';
 import 'health.dart';
 import 'message.dart';
 import 'render_tree.dart';
+import 'request_data.dart';
 import 'semantics.dart';
 
 const String _extensionMethodName = 'driver';
 const String _extensionMethod = 'ext.flutter.$_extensionMethodName';
 
-class _DriverBinding extends WidgetsFlutterBinding { // TODO(ianh): refactor so we're not extending a concrete binding
+typedef Future<String> DataHandler(String message);
+
+class _DriverBinding extends BindingBase with SchedulerBinding, GestureBinding, ServicesBinding, RendererBinding, WidgetsBinding {
+  _DriverBinding(this._handler);
+
+  final DataHandler _handler;
+
   @override
   void initServiceExtensions() {
     super.initServiceExtensions();
-    final FlutterDriverExtension extension = new FlutterDriverExtension();
+    final FlutterDriverExtension extension = new FlutterDriverExtension(_handler);
     registerServiceExtension(
       name: _extensionMethodName,
-      callback: extension.call
+      callback: extension.call,
     );
   }
 }
@@ -44,9 +53,12 @@ class _DriverBinding extends WidgetsFlutterBinding { // TODO(ianh): refactor so
 ///
 /// Call this function prior to running your application, e.g. before you call
 /// `runApp`.
-void enableFlutterDriverExtension() {
+///
+/// Optionally you can pass a [DataHandler] callback. It will be called if the
+/// test calls [FlutterDriver.requestData].
+void enableFlutterDriverExtension({ DataHandler handler }) {
   assert(WidgetsBinding.instance == null);
-  new _DriverBinding();
+  new _DriverBinding(handler);
   assert(WidgetsBinding.instance is _DriverBinding);
 }
 
@@ -62,18 +74,17 @@ typedef Finder FinderConstructor(SerializableFinder finder);
 
 @visibleForTesting
 class FlutterDriverExtension {
-  static final Logger _log = new Logger('FlutterDriverExtension');
-
-  FlutterDriverExtension() {
+  FlutterDriverExtension(this._requestDataHandler) {
     _commandHandlers.addAll(<String, CommandHandlerCallback>{
       'get_health': _getHealth,
       'get_render_tree': _getRenderTree,
-      'tap': _tap,
       'get_text': _getText,
-      'set_frame_sync': _setFrameSync,
-      'set_semantics': _setSemantics,
+      'request_data': _requestData,
       'scroll': _scroll,
       'scrollIntoView': _scrollIntoView,
+      'set_frame_sync': _setFrameSync,
+      'set_semantics': _setSemantics,
+      'tap': _tap,
       'waitFor': _waitFor,
       'waitUntilNoTransientCallbacks': _waitUntilNoTransientCallbacks,
     });
@@ -81,12 +92,13 @@ class FlutterDriverExtension {
     _commandDeserializers.addAll(<String, CommandDeserializerCallback>{
       'get_health': (Map<String, String> params) => new GetHealth.deserialize(params),
       'get_render_tree': (Map<String, String> params) => new GetRenderTree.deserialize(params),
-      'tap': (Map<String, String> params) => new Tap.deserialize(params),
       'get_text': (Map<String, String> params) => new GetText.deserialize(params),
-      'set_frame_sync': (Map<String, String> params) => new SetFrameSync.deserialize(params),
-      'set_semantics': (Map<String, String> params) => new SetSemantics.deserialize(params),
+      'request_data': (Map<String, String> params) => new RequestData.deserialize(params),
       'scroll': (Map<String, String> params) => new Scroll.deserialize(params),
       'scrollIntoView': (Map<String, String> params) => new ScrollIntoView.deserialize(params),
+      'set_frame_sync': (Map<String, String> params) => new SetFrameSync.deserialize(params),
+      'set_semantics': (Map<String, String> params) => new SetSemantics.deserialize(params),
+      'tap': (Map<String, String> params) => new Tap.deserialize(params),
       'waitFor': (Map<String, String> params) => new WaitFor.deserialize(params),
       'waitUntilNoTransientCallbacks': (Map<String, String> params) => new WaitUntilNoTransientCallbacks.deserialize(params),
     });
@@ -98,6 +110,10 @@ class FlutterDriverExtension {
     });
   }
 
+  final DataHandler _requestDataHandler;
+
+  static final Logger _log = new Logger('FlutterDriverExtension');
+
   final WidgetController _prober = new WidgetController(WidgetsBinding.instance);
   final Map<String, CommandHandlerCallback> _commandHandlers = <String, CommandHandlerCallback>{};
   final Map<String, CommandDeserializerCallback> _commandDeserializers = <String, CommandDeserializerCallback>{};
@@ -117,6 +133,7 @@ class FlutterDriverExtension {
   ///
   /// The returned JSON is command specific. Generally the caller deserializes
   /// the result into a subclass of [Result], but that's not strictly required.
+  @visibleForTesting
   Future<Map<String, dynamic>> call(Map<String, String> params) async {
     final String commandKind = params['command'];
     try {
@@ -243,8 +260,8 @@ class FlutterDriverExtension {
 
     _prober.binding.hitTest(hitTest, startLocation);
     _prober.binding.dispatchEvent(pointer.down(startLocation), hitTest);
-    await new Future<Null>.value();  // so that down and move don't happen in the same microtask
-    for (int moves = 0; moves < totalMoves; moves++) {
+    await new Future<Null>.value(); // so that down and move don't happen in the same microtask
+    for (int moves = 0; moves < totalMoves; moves += 1) {
       currentLocation = currentLocation + delta;
       _prober.binding.dispatchEvent(pointer.move(currentLocation), hitTest);
       await new Future<Null>.delayed(pause);
@@ -269,6 +286,11 @@ class FlutterDriverExtension {
     return new GetTextResult(text.data);
   }
 
+  Future<RequestDataResult> _requestData(Command command) async {
+    final RequestData requestDataCommand = command;
+    return new RequestDataResult(_requestDataHandler == null ? '' : await _requestDataHandler(requestDataCommand.message));
+  }
+
   Future<SetFrameSyncResult> _setFrameSync(Command command) async {
     final SetFrameSync setFrameSyncCommand = command;
     _frameSync = setFrameSyncCommand.enabled;

packages/flutter_driver/lib/src/frame_sync.dart

@@ -9,11 +9,11 @@ class SetFrameSync extends Command {
   @override
   final String kind = 'set_frame_sync';
 
+  SetFrameSync(this.enabled, { Duration timeout }) : super(timeout: timeout);
+
   /// Whether frameSync should be enabled or disabled.
   final bool enabled;
 
-  SetFrameSync(this.enabled, { Duration timeout }) : super(timeout: timeout);
-
   /// Deserializes this command from the value generated by [serialize].
   SetFrameSync.deserialize(Map<String, String> params)
       : this.enabled = params['enabled'].toLowerCase() == 'true',

packages/flutter_driver/lib/src/health.dart

@@ -10,12 +10,14 @@ class GetHealth extends Command {
   @override
   final String kind = 'get_health';
 
+  /// Create a health check command.
   GetHealth({Duration timeout}) : super(timeout: timeout);
 
   /// Deserializes the command from JSON generated by [serialize].
   GetHealth.deserialize(Map<String, String> json) : super.deserialize(json);
 }
 
+/// A description of application state.
 enum HealthStatus {
   /// Application is known to be in a good shape and should be able to respond.
   ok,
@@ -27,6 +29,8 @@ enum HealthStatus {
 final EnumIndex<HealthStatus> _healthStatusIndex =
     new EnumIndex<HealthStatus>(HealthStatus.values);
 
+/// A description of the application state, as provided in response to a
+/// [FlutterDriver.checkHealth] test.
 class Health extends Result {
   /// Creates a [Health] object with the given [status].
   Health(this.status) {
@@ -38,10 +42,13 @@ class Health extends Result {
     return new Health(_healthStatusIndex.lookupBySimpleName(json['status']));
   }
 
+  /// The status represented by this object.
+  ///
+  /// If the application responded, this will be [HealthStatus.ok].
   final HealthStatus status;
 
   @override
   Map<String, dynamic> toJson() => <String, dynamic>{
-    'status': _healthStatusIndex.toSimpleName(status)
+    'status': _healthStatusIndex.toSimpleName(status),
   };
 }

packages/flutter_driver/lib/src/request_data.dart

@@ -0,0 +1,46 @@
+// Copyright 2016 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 'message.dart';
+
+/// Send a string and get a string response.
+class RequestData extends Command {
+  @override
+  final String kind = 'request_data';
+
+  /// Create a command that sends a message.
+  RequestData(this.message, { Duration timeout }) : super(timeout: timeout);
+
+  /// The message being sent from the test to the application.
+  final String message;
+
+  /// Deserializes this command from the value generated by [serialize].
+  RequestData.deserialize(Map<String, String> params)
+      : this.message = params['message'],
+        super.deserialize(params);
+
+  @override
+  Map<String, String> serialize() => super.serialize()..addAll(<String, String>{
+    'message': message,
+  });
+}
+
+/// The result of the [RequestData] command.
+class RequestDataResult extends Result {
+  /// Creates a result with the given [message].
+  RequestDataResult(this.message);
+
+  /// The text extracted by the [RequestData] command.
+  final String message;
+
+  /// Deserializes the result from JSON.
+  static RequestDataResult fromJson(Map<String, dynamic> json) {
+    return new RequestDataResult(json['message']);
+  }
+
+  @override
+  Map<String, dynamic> toJson() => <String, String>{
+    'message': message,
+  };
+}

packages/flutter_driver/lib/src/semantics.dart

@@ -9,11 +9,11 @@ class SetSemantics extends Command {
   @override
   final String kind = 'set_semantics';
 
+  SetSemantics(this.enabled, { Duration timeout }) : super(timeout: timeout);
+
   /// Whether semantics should be enabled or disabled.
   final bool enabled;
 
-  SetSemantics(this.enabled, { Duration timeout }) : super(timeout: timeout);
-
   /// Deserializes this command from the value generated by [serialize].
   SetSemantics.deserialize(Map<String, String> params)
       : this.enabled = params['enabled'].toLowerCase() == 'true',

packages/flutter_driver/test/src/extension_test.dart

@@ -5,16 +5,19 @@
 import 'package:flutter/scheduler.dart';
 import 'package:flutter_driver/src/extension.dart';
 import 'package:flutter_driver/src/find.dart';
+import 'package:flutter_driver/src/request_data.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
   group('waitUntilNoTransientCallbacks', () {
     FlutterDriverExtension extension;
     Map<String, dynamic> result;
+    int messageId = 0;
+    final List<String> log = <String>[];
 
     setUp(() {
       result = null;
-      extension = new FlutterDriverExtension();
+      extension = new FlutterDriverExtension((String message) async { log.add(message); return (messageId += 1).toString(); });
     });
 
     testWidgets('returns immediately when transient callback queue is empty', (WidgetTester tester) async {
@@ -57,5 +60,12 @@ void main() {
           },
       );
     });
+
+    testWidgets('handler', (WidgetTester tester) async {
+      expect(log, isEmpty);
+      final dynamic result = RequestDataResult.fromJson((await extension.call(new RequestData('hello').serialize()))['response']);
+      expect(log, <String>['hello']);
+      expect(result.message, '1');
+    });
   });
 }

packages/flutter_tools/lib/src/commands/drive.dart

@@ -42,19 +42,22 @@ class DriveCommand extends RunCommandBase {
     argParser.addFlag(
       'keep-app-running',
       negatable: true,
-      defaultsTo: false,
       help:
         'Will keep the Flutter application running when done testing.\n'
-        'By default, Flutter drive stops the application after tests are finished.\n'
-        'Ignored if --use-existing-app is specified.'
+        'By default, "flutter drive" stops the application after tests are finished,\n'
+        'and --keep-app-running overrides this. On the other hand, if --use-existing-app\n'
+        'is specified, then "flutter drive" instead defaults to leaving the application\n'
+        'running, and --no-keep-app-running overrides it.'
     );
 
     argParser.addOption(
       'use-existing-app',
       help:
         'Connect to an already running instance via the given observatory URL.\n'
-        'If this option is given, the application will not be automatically started\n'
-        'or stopped.'
+        'If this option is given, the application will not be automatically started,\n'
+        'and it will only be stopped if --no-keep-app-running is explicitly set.',
+      valueHelp:
+        'url'
     );
   }
 
@@ -95,7 +98,7 @@ class DriveCommand extends RunCommandBase {
 
     String observatoryUri;
     if (argResults['use-existing-app'] == null) {
-      printStatus('Starting application: ${argResults["target"]}');
+      printStatus('Starting application: $targetFile');
 
       if (getBuildMode() == BuildMode.release) {
         // This is because we need VM service to be able to drive the app.
@@ -125,11 +128,11 @@ class DriveCommand extends RunCommandBase {
         rethrow;
       throwToolExit('CAUGHT EXCEPTION: $error\n$stackTrace');
     } finally {
-      if (!argResults['keep-app-running'] && argResults['use-existing-app'] == null) {
+      if (argResults['keep-app-running'] ?? (argResults['use-existing-app'] != null)) {
+        printStatus('Leaving the application running.');
+      } else {
         printStatus('Stopping application instance.');
         await appStopper(this);
-      } else {
-        printStatus('Leaving the application running.');
       }
     }
   }
@@ -137,7 +140,7 @@ class DriveCommand extends RunCommandBase {
   String _getTestFile() {
     String appFile = fs.path.normalize(targetFile);
 
-    // This command extends `flutter start` and therefore CWD == package dir
+    // This command extends `flutter run` and therefore CWD == package dir
     final String packageDir = fs.currentDirectory.path;
 
     // Make appFile path relative to package directory because we are looking
@@ -209,7 +212,7 @@ Future<Device> findTargetDevice() async {
 /// Starts the application on the device given command configuration.
 typedef Future<LaunchResult> AppStarter(DriveCommand command);
 
-AppStarter appStarter = _startApp;
+AppStarter appStarter = _startApp; // (mutable for testing)
 void restoreAppStarter() {
   appStarter = _startApp;
 }
@@ -255,7 +258,7 @@ Future<LaunchResult> _startApp(DriveCommand command) async {
       observatoryPort: command.observatoryPort,
       diagnosticPort: command.diagnosticPort,
     ),
-    platformArgs: platformArgs
+    platformArgs: platformArgs,
   );
 
   if (!result.started) {

packages/flutter_tools/lib/src/commands/run.dart

@@ -317,8 +317,8 @@ class RunCommand extends RunCommandBase {
     }
 
     DateTime appStartedTime;
-    // Sync completer so the completing agent attaching to the resident doesn't 
-    // need to know about analytics. 
+    // Sync completer so the completing agent attaching to the resident doesn't
+    // need to know about analytics.
     //
     // Do not add more operations to the future.
     final Completer<Null> appStartedTimeRecorder = new Completer<Null>.sync();
@@ -338,7 +338,7 @@ class RunCommand extends RunCommandBase {
       analyticsParameters: <String>[
         hotMode ? 'hot' : 'cold',
         getModeName(getBuildMode()),
-        devices.length == 1 
+        devices.length == 1
             ? getNameForTargetPlatform(await devices[0].targetPlatform)
             : 'multiple',
         devices.length == 1 && await devices[0].isLocalEmulator ? 'emulator' : null

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

@@ -7,7 +7,6 @@ import '../base/io.dart' show Process;
 
 /// Callbacks for reporting progress while running tests.
 class TestWatcher {
-
   /// Called after a child process starts.
   ///
   /// If startPaused was true, the caller needs to resume in Observatory to