Error Handling

Priority: P1 (HIGH)

Standardized functional error handling using dartz and freezed failures.

Implementation Guidelines

• Either Pattern: Return Either<Failure, T> from repositories. No exceptions in UI/BLoC.
• Failures: Define domain-specific failures using @freezed unions.
• Mapping: Infrastructure catches Exception and returns Left(Failure).
• Consumption: Use .fold(failure, success) in BLoC to emit corresponding states.
• Typed Errors: Use left(Failure()) and right(Value()) from Dartz.
• Low-Cardinality Logging: Use stable message templates; pass variable data via metadata/context.
• Layer Restriction: try/catch only in Infrastructure. UI/Application should not catch.
• Failure Mapping: Convert external exceptions with FailureHandler.handleFailure(e).
• Localization: Use failure.failureMessage (returns TRObject) for UI-safe text.
• Right/Left Restriction: Only Infrastructure may construct Right()/Left().
• No Silent Catch: Never swallow errors without logging or a documented retry.

Reference & Examples

For Failure definitions and API error mapping: See references/REFERENCE.md.

Related Topics

layer-based-clean-architecture | bloc-state-management

🚫 Anti-Patterns

• Do NOT use standard patterns if specific project rules exist.
• Do NOT ignore error handling or edge cases.