flutter · albertusdev · Oct 28, 2019 · Oct 13, 2019 · Oct 14, 2019 · Oct 14, 2019
diff --git a/packages/flutter/lib/src/animation/animations.dart b/packages/flutter/lib/src/animation/animations.dart
@@ -439,12 +439,14 @@ class CurvedAnimation extends Animation<double> with AnimationWithParentMixin<do
         final double transformedValue = activeCurve.transform(t);
         final double roundedTransformedValue = transformedValue.round().toDouble();
         if (roundedTransformedValue != t) {
-          throw FlutterError(
-            'Invalid curve endpoint at $t.\n'
-            'Curves must map 0.0 to near zero and 1.0 to near one but '
-            '${activeCurve.runtimeType} mapped $t to $transformedValue, which '
-            'is near $roundedTransformedValue.'
-          );
+          throw FlutterError.fromParts(<DiagnosticsNode>[
+            ErrorSummary('Invalid curve endpoint at $t.'),
+            ErrorDescription(
+              'Curves must map 0.0 to near zero and 1.0 to near one but '
+              '${activeCurve.runtimeType} mapped $t to $transformedValue, which '
+              'is near $roundedTransformedValue.'
+            )
+          ]);
         }
         return true;
       }());

diff --git a/packages/flutter/lib/src/cupertino/tab_view.dart b/packages/flutter/lib/src/cupertino/tab_view.dart
@@ -192,29 +192,33 @@ class _CupertinoTabViewState extends State<CupertinoTabView> {
   Route<dynamic> _onUnknownRoute(RouteSettings settings) {
     assert(() {
       if (widget.onUnknownRoute == null) {
-        throw 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 "builder" 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 "builder" and "routes".\n'
-          ' 4. Finally if all else fails onUnknownRoute is called.\n'
-          'Unfortunately, onUnknownRoute was not set.'
-        );
+        throw FlutterError.fromParts(<DiagnosticsNode>[
+          ErrorSummary('Could not find a generator for route $settings in the $runtimeType.'),
+          ErrorDescription(
+            'Generators for routes are searched for in the following order:\n'
+            ' 1. For the "/" route, the "builder" 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 "builder" 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 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.'
-        );
+        throw FlutterError.fromParts(<DiagnosticsNode>[
+          ErrorSummary('The onUnknownRoute callback returned null.'),
+          ErrorDescription(
+            'When the $runtimeType requested the route $settings from its '
+            'onUnknownRoute callback, the callback returned null. Such callbacks '
+            'must never return null.'
+          )
+        ]);
       }
       return true;
     }());

diff --git a/packages/flutter/lib/src/foundation/change_notifier.dart b/packages/flutter/lib/src/foundation/change_notifier.dart
@@ -102,10 +102,10 @@ class ChangeNotifier implements Listenable {
   bool _debugAssertNotDisposed() {
     assert(() {
       if (_listeners == null) {
-        throw FlutterError(
-          'A $runtimeType was used after being disposed.\n'
-          'Once you have called dispose() on a $runtimeType, it can no longer be used.'
-        );
+        throw FlutterError.fromParts(<DiagnosticsNode>[
+          ErrorSummary('A $runtimeType was used after being disposed.'),
+          ErrorDescription('Once you have called dispose() on a $runtimeType, it can no longer be used.')
+        ]);
       }
       return true;
     }());

diff --git a/packages/flutter/lib/src/material/debug.dart b/packages/flutter/lib/src/material/debug.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
 import 'material.dart';
@@ -24,45 +25,26 @@ import 'scaffold.dart' show Scaffold;
 bool debugCheckHasMaterial(BuildContext context) {
   assert(() {
     if (context.widget is! Material && context.ancestorWidgetOfExactType(Material) == null) {
-      final StringBuffer message = StringBuffer();
-      message.writeln('No Material widget found.');
-      message.writeln(
-        '${context.widget.runtimeType} widgets require a Material '
-        'widget ancestor.'
+      throw FlutterError.fromParts(<DiagnosticsNode>[
+        ErrorSummary('No Material widget found.'),
+        ErrorDescription(
+          '${context.widget.runtimeType} widgets require a Material '
+          'widget ancestor.\n'
+          'In material design, most widgets are conceptually "printed" on '
+          'a sheet of material. In Flutter\'s material library, that '
+          'material is represented by the Material widget. It is the '
+          'Material widget that renders ink splashes, for instance. '
+          'Because of this, many material library widgets require that '
+          'there be a Material widget in the tree above them.'
+        ),
+        ErrorHint(
+          'To introduce a Material widget, you can either directly '
+          'include one, or use a widget that contains Material itself, '
+          'such as a Card, Dialog, Drawer, or Scaffold.',
+        ),
+        ...context.describeMissingAncestor(expectedAncestorType: Material)
+      ]
       );
-      message.writeln(
-        'In material design, most widgets are conceptually "printed" on '
-        'a sheet of material. In Flutter\'s material library, that '
-        'material is represented by the Material widget. It is the '
-        'Material widget that renders ink splashes, for instance. '
-        'Because of this, many material library widgets require that '
-        'there be a Material widget in the tree above them.'
-      );
-      message.writeln(
-        'To introduce a Material widget, you can either directly '
-        'include one, or use a widget that contains Material itself, '
-        'such as a Card, Dialog, Drawer, or Scaffold.'
-      );
-      message.writeln(
-        'The specific widget that could not find a Material 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  $ancestor');
-      } else {
-        message.writeln(
-          'This widget is the root of the tree, so it has no '
-          'ancestors, let alone a "Material" ancestor.'
-        );
-      }
-      throw FlutterError(message.toString());
     }
     return true;
   }());
@@ -87,42 +69,24 @@ bool debugCheckHasMaterial(BuildContext context) {
 bool debugCheckHasMaterialLocalizations(BuildContext context) {
   assert(() {
     if (Localizations.of<MaterialLocalizations>(context, MaterialLocalizations) == null) {
-      final StringBuffer message = StringBuffer();
-      message.writeln('No MaterialLocalizations found.');
-      message.writeln(
-        '${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  $ancestor');
-      } else {
-        message.writeln(
-          'This widget is the root of the tree, so it has no '
-          'ancestors, let alone a "Localizations" ancestor.'
-        );
-      }
-      throw FlutterError(message.toString());
+      throw FlutterError.fromParts(<DiagnosticsNode>[
+        ErrorSummary('No MaterialLocalizations found.'),
+        ErrorDescription(
+          '${context.widget.runtimeType} widgets require MaterialLocalizations '
+          'to be provided by a Localizations widget ancestor.'
+        ),
+        ErrorDescription(
+          'Localizations are used to generate many different messages, labels,'
+          'and abbreviations which are used by the material library.'
+        ),
+        ErrorHint(
+          '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.'
+        ),
+        ...context.describeMissingAncestor(expectedAncestorType: MaterialLocalizations)
+      ]);
     }
     return true;
   }());
@@ -145,17 +109,15 @@ bool debugCheckHasMaterialLocalizations(BuildContext context) {
 bool debugCheckHasScaffold(BuildContext context) {
   assert(() {
     if (context.widget is! Scaffold && context.ancestorWidgetOfExactType(Scaffold) == null) {
-      final Element element = context;
-      throw FlutterError(
-          'No Scaffold widget found.\n'
-          '${context.widget.runtimeType} widgets require a Scaffold widget ancestor.\n'
-          'The Specific widget that could not find a Scaffold ancestor was:\n'
-          '  ${context.widget}\n'
-          'The ownership chain for the affected widget is:\n'
-          '  ${element.debugGetCreatorChain(10)}\n'
+      throw FlutterError.fromParts(<DiagnosticsNode>[
+        ErrorSummary('No Scaffold widget found.'),
+        ErrorDescription('${context.widget.runtimeType} widgets require a Scaffold widget ancestor.'),
+        ...context.describeMissingAncestor(expectedAncestorType: Scaffold),
+        ErrorHint(
           'Typically, the Scaffold widget is introduced by the MaterialApp or '
           'WidgetsApp widget at the top of your application widget tree.'
-      );
+        )
+      ]);
     }
     return true;
   }());

diff --git a/packages/flutter/lib/src/material/page.dart b/packages/flutter/lib/src/material/page.dart
@@ -87,10 +87,10 @@ class MaterialPageRoute<T> extends PageRoute<T> {
     final Widget result = builder(context);
     assert(() {
       if (result == null) {
-        throw FlutterError(
-          'The builder for route "${settings.name}" returned null.\n'
-          'Route builders must never return null.'
-        );
+        throw FlutterError.fromParts(<DiagnosticsNode>[
+          ErrorSummary('The builder for route "${settings.name}" returned null.'),
+          ErrorDescription('Route builders must never return null.')
+        ]);
       }
       return true;
     }());