[listen] Makes error context non-null

packages/listen/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.0.0-beta.4
+
+- `ErrorContext` is now a required positional, non-nullable parameter.
+
 ## 1.0.0-beta.3
 
 - Updates `ErrorCallback` to pass the raw error object and original `StackTrace`.

packages/listen/lib/src/listen.dart

@@ -20,8 +20,13 @@ enum ErrorContext {
 }
 
 /// Signature of callbacks that are called when an error is reported by a listener or assertion.
-typedef ErrorCallback =
-    void Function(Object error, StackTrace? stackTrace, {ErrorContext? context});
+///
+/// The cause of the error can be read from `context`.
+///
+/// See also:
+///
+///  * [ErrorContext], which identifies the context in which an error was reported.
+typedef ErrorCallback = void Function(Object error, StackTrace? stackTrace, ErrorContext context);
 
 /// Signature of callbacks that are called when an object is created.
 ///
@@ -71,7 +76,7 @@ abstract class Listenable {
   /// Error callback that is called when an error is thrown by a listener or assertion.
   ///
   /// By default, errors are rethrown preserving their original [StackTrace].
-  static ErrorCallback onError = (Object error, StackTrace? stackTrace, {ErrorContext? context}) {
+  static ErrorCallback onError = (Object error, StackTrace? stackTrace, ErrorContext context) {
     Error.throwWithStackTrace(error, stackTrace ?? StackTrace.current);
   };
 
@@ -187,7 +192,7 @@ mixin class ChangeNotifier implements Listenable {
             'can no longer be used.',
           ),
           StackTrace.current,
-          context: ErrorContext.assertion,
+          ErrorContext.assertion,
         );
       }
       return true;
@@ -437,7 +442,7 @@ mixin class ChangeNotifier implements Listenable {
       try {
         _listeners[i]?.call();
       } catch (exception, stack) {
-        Listenable.onError(exception, stack, context: ErrorContext.listener);
+        Listenable.onError(exception, stack, ErrorContext.listener);
       }
     }
 

packages/listen/pubspec.yaml

@@ -5,7 +5,7 @@ name: listen
 description: A package to notify state changes to interested listeners in pure Dart.
 repository: https://github.com/flutter/core-packages/tree/main/packages/listen
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+listen%22
-version: 1.0.0-beta.3
+version: 1.0.0-beta.4
 
 environment:
   sdk: ^3.10.0

packages/listen/test/listen_test.dart

@@ -60,7 +60,7 @@ void main() {
   setUp(() {
     lastError = null;
     lastContext = null;
-    Listenable.onError = (Object error, StackTrace? stackTrace, {ErrorContext? context}) {
+    Listenable.onError = (Object error, StackTrace? stackTrace, ErrorContext context) {
       lastError = error;
       lastContext = context;
     };
@@ -116,7 +116,7 @@ void main() {
 
     final ErrorCallback original = Listenable.onError;
     final List<Object> errors = [];
-    Listenable.onError = (Object error, StackTrace? stackTrace, {ErrorContext? context}) {
+    Listenable.onError = (Object error, StackTrace? stackTrace, ErrorContext context) {
       errors.add(error);
     };
     addTearDown(() {
@@ -190,7 +190,7 @@ void main() {
   test('Listenable.onError preserves runtime exception types', () {
     final List<Object> errors = [];
     final ErrorCallback original = Listenable.onError;
-    Listenable.onError = (Object error, StackTrace? stackTrace, {ErrorContext? context}) {
+    Listenable.onError = (Object error, StackTrace? stackTrace, ErrorContext context) {
       errors.add(error);
     };
     addTearDown(() {
@@ -210,7 +210,7 @@ void main() {
   test('Listenable.onError default implementation rethrows and preserves StackTrace', () {
     final stack = StackTrace.fromString('test_stack_trace_marker');
     try {
-      originalOnError(const FormatException('bad format'), stack);
+      originalOnError(const FormatException('bad format'), stack, ErrorContext.listener);
       fail('Expected originalOnError to throw');
     } catch (e, s) {
       expect(e, isA<FormatException>());
@@ -221,7 +221,7 @@ void main() {
   test('Listenable.onError reports correct ErrorContext across all failure types', () {
     final List<ErrorContext?> contexts = [];
     final ErrorCallback original = Listenable.onError;
-    Listenable.onError = (Object error, StackTrace? stackTrace, {ErrorContext? context}) {
+    Listenable.onError = (Object error, StackTrace? stackTrace, ErrorContext context) {
       contexts.add(context);
     };
     addTearDown(() {