Support overriding ErrorWidget.builder (flutter#6302)

*List which issues are fixed by this PR. You must list at least one issue.*
Issue: flutter/flutter#144960

Author: peixinli

packages/rfw/.gitignore

@@ -76,3 +76,6 @@ build/
 !**/ios/**/default.mode2v3
 !**/ios/**/default.pbxuser
 !**/ios/**/default.perspectivev3
+
+# Coverage
+coverage/

packages/rfw/CHANGELOG.md

@@ -1,3 +1,6 @@
+## 1.0.26
+* Supports overriding the error widget builder.
+
 ## 1.0.25
 * Adds support for wildget builders.
 

packages/rfw/lib/src/flutter/runtime.dart

@@ -1559,11 +1559,12 @@ class _Subscription {
   }
 }
 
-ErrorWidget _buildErrorWidget(String message) {
-  FlutterError.reportError(FlutterErrorDetails(
+Widget _buildErrorWidget(String message) {
+  final FlutterErrorDetails detail = FlutterErrorDetails(
     exception: message,
     stack: StackTrace.current,
     library: 'Remote Flutter Widgets',
-  ));
-  return ErrorWidget(message);
+  );
+  FlutterError.reportError(detail);
+  return ErrorWidget.builder(detail);
 }

packages/rfw/pubspec.yaml

@@ -2,7 +2,7 @@ name: rfw
 description: "Remote Flutter widgets: a library for rendering declarative widget description files at runtime."
 repository: https://github.com/flutter/packages/tree/main/packages/rfw
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+rfw%22
-version: 1.0.25
+version: 1.0.26
 
 environment:
   sdk: ^3.2.0

packages/rfw/test/runtime_test.dart

@@ -244,7 +244,7 @@ void main() {
       ),
     );
     expect(tester.takeException().toString(), contains('Could not find remote widget named'));
-    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, 'Could not find remote widget named widget in a, possibly because some dependencies were missing: b');
+    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, contains('Could not find remote widget named widget in a, possibly because some dependencies were missing: b'));
   });
 
   testWidgets('Missing libraries in specified widget', (WidgetTester tester) async {
@@ -258,7 +258,7 @@ void main() {
       ),
     );
     expect(tester.takeException().toString(), contains('Could not find remote widget named'));
-    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, 'Could not find remote widget named widget in a, possibly because some dependencies were missing: a');
+    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, contains('Could not find remote widget named widget in a, possibly because some dependencies were missing: a'));
   });
 
   testWidgets('Missing libraries in import via dependency', (WidgetTester tester) async {
@@ -276,7 +276,7 @@ void main() {
       ),
     );
     expect(tester.takeException().toString(), contains('Could not find remote widget named'));
-    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, 'Could not find remote widget named test in a, possibly because some dependencies were missing: b');
+    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, contains('Could not find remote widget named test in a, possibly because some dependencies were missing: b'));
   });
 
   testWidgets('Missing widget', (WidgetTester tester) async {
@@ -291,7 +291,7 @@ void main() {
       ),
     );
     expect(tester.takeException().toString(), contains('Could not find remote widget named'));
-    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, 'Could not find remote widget named widget in a.');
+    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, contains('Could not find remote widget named widget in a.'));
   });
 
   testWidgets('Runtime', (WidgetTester tester) async {
@@ -1152,7 +1152,29 @@ void main() {
 
     expect(tester.takeException().toString(), contains(expectedErrorMessage));
     expect(find.byType(ErrorWidget), findsOneWidget);
-    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, expectedErrorMessage);
+    expect(tester.widget<ErrorWidget>(find.byType(ErrorWidget)).message, contains(expectedErrorMessage));
+  });
+
+
+  testWidgets('Customized error widget', (WidgetTester tester) async {
+    final ErrorWidgetBuilder oldBuilder = ErrorWidget.builder;
+    ErrorWidget.builder = (FlutterErrorDetails details) {
+      return const Text('oopsie!', textDirection: TextDirection.ltr);
+    };
+    final Runtime runtime = Runtime()
+      ..update(const LibraryName(<String>['a']), parseLibraryFile(''));
+    final DynamicContent data = DynamicContent();
+    await tester.pumpWidget(
+      RemoteWidget(
+        runtime: runtime,
+        data: data,
+        widget: const FullyQualifiedWidgetName(LibraryName(<String>['a']), 'widget'),
+      ),
+    );
+    expect(tester.takeException().toString(), contains('Could not find remote widget named'));
+    expect(find.text('oopsie!'), findsOneWidget);
+    expect(find.byType(ErrorWidget), findsNothing);
+    ErrorWidget.builder = oldBuilder;
   });
 
   testWidgets('Widget builders - work when scope is not used', (WidgetTester tester) async {