fix(mix): report FlutterErrorDetails in debug mode when Prop value conversion fails

[leoafarias]

Summary

Replaces the silent debugPrint('Mix: could not convert value of type ...') inside assert in Prop.resolveProp with FlutterError.reportError(FlutterErrorDetails(...)) so that failed Mix<V> conversions surface through Flutter's standard error pipeline (FlutterError.onError) in debug/test mode while still returning the fallback resolved value without crashing the widget build.

Root Cause & Motivation

When a Prop<V> accumulates both a Mix<V> source (e.g. a custom Mix<double> subclass passed via Prop.mix(...)) and a plain value source (ValueSource<V> or TokenSource<V> resolving to V), hasMixValues is true and Prop.resolveProp converts every non-Mix<V> entry via MixConverterRegistry.instance.tryConvert<V>(value).

Previously, when no MixConverter<V> was registered (such as for scalar double), Prop.resolveProp only called debugPrint inside an assert block and silently dropped the unconverted value. Because debugPrint does not route through FlutterError.onError, invalid Mix<V> + scalar V combinations went unnoticed in flutter test while printing console noise on every animation frame.

Using FlutterError.reportError(FlutterErrorDetails(...)) inside the assert(() { ... return true; }()) block follows Flutter's standard non-fatal error reporting pattern (like RenderFlex overflow):

• Never crashes in production or debug: resolveProp continues and returns the resolved fallback value in both debug and release builds instead of throwing mid-build.
• Zero overhead in release/profile builds: The assert block is stripped in release builds.
• Fails flutter test automatically: TestWidgetsFlutterBinding hooks FlutterError.onError, so widget tests fail immediately (and tester.takeException() captures the FlutterError).

Verification

• Added unit test in packages/mix/test/src/core/prop_test.dart verifying that merging a ValueSource<double> with a custom Mix<double> reports FlutterErrorDetails via FlutterError.onError and still returns the resolved fallback value (20.0).
• flutter test test/src/core/prop_test.dart
• dart analyze lib/src/core/prop.dart test/src/core/prop_test.dart

[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-15T20:57:52.262859Z	328b63d	New commits

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Throw instead of only reporting conversion failures

When a converter is missing in a debug build, FlutterError.reportError invokes the global FlutterError.onError handler and then returns; it does not throw. Consequently, resolveProp still drops the unconverted value and returns the remaining Mix result, and a handler can swallow the error exactly as this new test does, so the intended fail-fast behavior is not implemented. Throw the FlutterError from the assertion block and test with throwsA if resolution is meant to abort.

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