Add debug check for localization parent (flutter#20787)

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

@@ -109,6 +109,7 @@ class AboutListTile extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
+    assert(debugCheckHasMaterialLocalizations(context));
     return ListTile(
       leading: icon,
       title: child ??
@@ -263,6 +264,7 @@ class AboutDialog extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     final String name = applicationName ?? _defaultApplicationName(context);
     final String version = applicationVersion ?? _defaultApplicationVersion(context);
     final Widget icon = applicationIcon ?? _defaultApplicationIcon(context);
@@ -437,6 +439,7 @@ class _LicensePageState extends State<LicensePage> {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     final String name = widget.applicationName ?? _defaultApplicationName(context);
     final String version = widget.applicationVersion ?? _defaultApplicationVersion(context);
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);

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

@@ -11,6 +11,7 @@ import 'package:flutter/widgets.dart';
 
 import 'back_button.dart';
 import 'constants.dart';
+import 'debug.dart';
 import 'flexible_space_bar.dart';
 import 'icon_button.dart';
 import 'icons.dart';
@@ -332,6 +333,7 @@ class _AppBarState extends State<AppBar> {
   @override
   Widget build(BuildContext context) {
     assert(!widget.primary || debugCheckHasMediaQuery(context));
+    assert(debugCheckHasMaterialLocalizations(context));
     final ThemeData themeData = Theme.of(context);
     final ScaffoldState scaffold = Scaffold.of(context, nullOk: true);
     final ModalRoute<dynamic> parentRoute = ModalRoute.of(context);

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

@@ -4,6 +4,7 @@
 
 import 'package:flutter/widgets.dart';
 
+import 'debug.dart';
 import 'icon_button.dart';
 import 'icons.dart';
 import 'material_localizations.dart';
@@ -81,6 +82,7 @@ class BackButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     return IconButton(
       icon: const BackButtonIcon(),
       color: color,

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

@@ -10,6 +10,7 @@ import 'package:vector_math/vector_math_64.dart' show Vector3;
 
 import 'colors.dart';
 import 'constants.dart';
+import 'debug.dart';
 import 'ink_well.dart';
 import 'material.dart';
 import 'material_localizations.dart';
@@ -495,6 +496,7 @@ class _BottomNavigationBarState extends State<BottomNavigationBar> with TickerPr
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasDirectionality(context));
+    assert(debugCheckHasMaterialLocalizations(context));
 
     // Labels apply up to _bottomMargin padding. Remainder is media padding.
     final double additionalBottomPadding = math.max(MediaQuery.of(context).padding.bottom - _kBottomMargin, 0.0);

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

@@ -8,6 +8,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';
+import 'debug.dart';
 import 'material.dart';
 import 'material_localizations.dart';
 import 'scaffold.dart';
@@ -315,6 +316,7 @@ Future<T> showModalBottomSheet<T>({
 }) {
   assert(context != null);
   assert(builder != null);
+  assert(debugCheckHasMaterialLocalizations(context));
   return Navigator.push(context, _ModalBottomSheetRoute<T>(
     builder: builder,
     theme: Theme.of(context, shadowThemeOnly: true),

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

@@ -1429,6 +1429,7 @@ class _RawChipState extends State<RawChip> with TickerProviderStateMixin<RawChip
     assert(debugCheckHasMaterial(context));
     assert(debugCheckHasMediaQuery(context));
     assert(debugCheckHasDirectionality(context));
+    assert(debugCheckHasMaterialLocalizations(context));
 
     final ThemeData theme = Theme.of(context);
     final ChipThemeData chipTheme = ChipTheme.of(context);

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

@@ -945,6 +945,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     final ThemeData theme = Theme.of(context);
     final Widget picker = Flexible(
       child: SizedBox(

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

@@ -5,6 +5,7 @@
 import 'package:flutter/widgets.dart';
 
 import 'material.dart';
+import 'material_localizations.dart';
 
 /// Asserts that the given context has a [Material] ancestor.
 ///
@@ -66,3 +67,63 @@ bool debugCheckHasMaterial(BuildContext context) {
   }());
   return true;
 }
+
+
+/// Asserts that the given context has a [Localizations] ancestor that contains
+/// a [MaterialLocalizations] delegate.
+///
+/// Used by many material design widgets to make sure that they are
+/// only used in contexts where they have access to localizations.
+///
+/// To call this function, use the following pattern, typically in the
+/// relevant Widget's build method:
+///
+/// ```dart
+/// assert(debugCheckHasMaterialLocalizations(context));
+/// ```
+///
+/// Does nothing if asserts are disabled. Always returns true.
+bool debugCheckHasMaterialLocalizations(BuildContext context) {
+  assert(() {
+    if (Localizations.of<MaterialLocalizations>(context, MaterialLocalizations) == null) {
+      final StringBuffer message = StringBuffer();
+      message.writeln('No MaterialLocalizations found.');
+      message.writeln(
+        '${context.widget.runtimeType} widgets require MaterialLocalizations '
+        'to be provided by a Localizations widget ancestor.'
+      );
+      message.writeln(
+        'Localizations are used to generate many different messages, labels,'
+        'and abbreviations which are used by the material library. '
+      );
+      message.writeln(
+        'To introduce a MaterialLocalizations, either use a '
+        ' MaterialApp at the root of your application to include them '
+        'automatically, or add a Localization widget with a '
+        'MaterialLocalizations delegate.'
+      );
+      message.writeln(
+        'The specific widget that could not find a MaterialLocalizations ancestor was:'
+      );
+      message.writeln('  ${context.widget}');
+      final List<Widget> ancestors = <Widget>[];
+      context.visitAncestorElements((Element element) {
+        ancestors.add(element.widget);
+        return true;
+      });
+      if (ancestors.isNotEmpty) {
+        message.write('The ancestors of this widget were:');
+        for (Widget ancestor in ancestors)
+          message.write('\n  $ancestor');
+      } else {
+        message.writeln(
+          'This widget is the root of the tree, so it has no '
+          'ancestors, let alone a "Localizations" ancestor.'
+        );
+      }
+      throw FlutterError(message.toString());
+    }
+    return true;
+  }());
+  return true;
+}

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

@@ -11,6 +11,7 @@ import 'package:flutter/widgets.dart';
 import 'button_bar.dart';
 import 'button_theme.dart';
 import 'colors.dart';
+import 'debug.dart';
 import 'ink_well.dart';
 import 'material.dart';
 import 'material_localizations.dart';
@@ -232,6 +233,7 @@ class AlertDialog extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     final List<Widget> children = <Widget>[];
     String label = semanticLabel;
 
@@ -490,6 +492,7 @@ class SimpleDialog extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     final List<Widget> body = <Widget>[];
     String label = semanticLabel;
 
@@ -596,6 +599,7 @@ Future<T> showDialog<T>({
   WidgetBuilder builder,
 }) {
   assert(child == null || builder == null);
+  assert(debugCheckHasMaterialLocalizations(context));
   return showGeneralDialog(
     context: context,
     pageBuilder: (BuildContext buildContext, Animation<double> animation, Animation<double> secondaryAnimation) {

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

@@ -6,6 +6,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';
+import 'debug.dart';
 import 'list_tile.dart';
 import 'material.dart';
 import 'material_localizations.dart';
@@ -116,6 +117,7 @@ class Drawer extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     String label = semanticLabel;
     switch (defaultTargetPlatform) {
       case TargetPlatform.iOS:
@@ -431,6 +433,7 @@ class DrawerControllerState extends State<DrawerController> with SingleTickerPro
   }
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     return ListTileTheme(
       style: ListTileStyle.drawer,
       child: _buildDrawer(context),

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

@@ -139,6 +139,7 @@ class _DropdownMenuState<T> extends State<_DropdownMenu<T>> {
     //
     // When the menu is dismissed we just fade the entire thing out
     // in the first 0.25s.
+    assert(debugCheckHasMaterialLocalizations(context));
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);
     final _DropdownRoute<T> route = widget.route;
     final double unit = 0.5 / (route.items.length + 1.5);
@@ -631,6 +632,7 @@ class _DropdownButtonState<T> extends State<DropdownButton<T>> with WidgetsBindi
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
+    assert(debugCheckHasMaterialLocalizations(context));
 
     // The width of the button and the menu are defined by the widest
     // item and the width of the hint.

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

@@ -109,6 +109,7 @@ class _ExpandIconState extends State<ExpandIcon> with SingleTickerProviderStateM
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
+    assert(debugCheckHasMaterialLocalizations(context));
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);
     final ThemeData theme = Theme.of(context);
     final String onTapHint = widget.isExpanded ? localizations.expandedIconTapHint : localizations.collapsedIconTapHint;

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

@@ -12,6 +12,7 @@ import 'button_theme.dart';
 import 'card.dart';
 import 'data_table.dart';
 import 'data_table_source.dart';
+import 'debug.dart';
 import 'dropdown.dart';
 import 'icon_button.dart';
 import 'icons.dart';
@@ -286,6 +287,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
   @override
   Widget build(BuildContext context) {
     // TODO(ianh): This whole build function doesn't handle RTL yet.
+    assert(debugCheckHasMaterialLocalizations(context));
     final ThemeData themeData = Theme.of(context);
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);
     // HEADER

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

@@ -8,6 +8,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
 import 'constants.dart';
+import 'debug.dart';
 import 'divider.dart';
 import 'icon_button.dart';
 import 'icons.dart';
@@ -713,6 +714,7 @@ Future<T> showMenu<T>({
 }) {
   assert(context != null);
   assert(items != null && items.isNotEmpty);
+  assert(debugCheckHasMaterialLocalizations(context));
   String label = semanticLabel;
   switch (defaultTargetPlatform) {
     case TargetPlatform.iOS:
@@ -911,6 +913,7 @@ class _PopupMenuButtonState<T> extends State<PopupMenuButton<T>> {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     return widget.child != null
       ? InkWell(
           onTap: showButtonMenu,

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

@@ -7,6 +7,7 @@ import 'dart:math';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
 
+import 'debug.dart';
 import 'material.dart';
 import 'material_localizations.dart';
 
@@ -510,6 +511,7 @@ class _ReorderableListContentState extends State<_ReorderableListContent> with T
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     // We use the layout builder to constrain the cross-axis size of dragging child widgets.
     return LayoutBuilder(builder: (BuildContext context, BoxConstraints constraints) {
         final List<Widget> wrappedChildren = <Widget>[];

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

@@ -9,6 +9,7 @@ import 'package:flutter/widgets.dart';
 
 import 'app_bar.dart';
 import 'colors.dart';
+import 'debug.dart';
 import 'input_border.dart';
 import 'input_decorator.dart';
 import 'material_localizations.dart';
@@ -389,6 +390,7 @@ class _SearchPageState<T> extends State<_SearchPage<T>> {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMaterialLocalizations(context));
     final ThemeData theme = widget.delegate.appBarTheme(context);
     final String searchFieldLabel = MaterialLocalizations.of(context).searchFieldLabel;
     Widget body;

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

@@ -540,6 +540,8 @@ class _TextFieldState extends State<TextField> with AutomaticKeepAliveClientMixi
   Widget build(BuildContext context) {
     super.build(context); // See AutomaticKeepAliveClientMixin.
     assert(debugCheckHasMaterial(context));
+    // TODO(jonahwilliams): uncomment out this check once we have migrated tests.
+    // assert(debugCheckHasMaterialLocalizations(context));
     assert(debugCheckHasDirectionality(context));
     final ThemeData themeData = Theme.of(context);
     final TextStyle style = widget.style ?? themeData.textTheme.subhead;

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

@@ -79,6 +79,7 @@ class _AccountDetails extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasDirectionality(context));
+    assert(debugCheckHasMaterialLocalizations(context));
 
     final ThemeData theme = Theme.of(context);
     final List<Widget> children = <Widget>[];
@@ -308,6 +309,7 @@ class _UserAccountsDrawerHeaderState extends State<UserAccountsDrawerHeader> {
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
+    assert(debugCheckHasMaterialLocalizations(context));
     return Semantics(
       container: true,
       label: MaterialLocalizations.of(context).signedInLabel,