CONVENTION.md

Conventions

Using lib/types.dart

Prefer the generated handler typedefs and helper classes from lib/types.dart whenever you expose IAP APIs from this package. They track the OpenIAP schema and guarantee consistent parameter and return shapes across the codebase.

Preferred pattern

final queryHandlers = QueryHandlers(
  fetchProducts: ({required ProductRequest params}) async {
    return _platform.fetchProducts(params: params);
  },
);

final mutationHandlers = MutationHandlers(
  finishTransaction: ({
    required PurchaseInput purchase,
    bool? isConsumable,
  }) async {
    return _platform.finishTransaction(
      purchase: purchase,
      isConsumable: isConsumable,
    );
  },
);

The generated signatures (QueryFetchProductsHandler, MutationFinishTransactionHandler, etc.) keep API contracts in sync with the schema. They also surface nullability, optional flags, and platform-specific fields without repeating boilerplate.

Keep API surfaces self-contained

• lib/flutter_inapp_purchase.dart should expose only the generated API handlers. Avoid introducing private helper methods inside that file; derive request payloads inline or delegate to shared helpers in lib/helpers.dart when logic needs to be shared.
• When a reusable helper becomes unavoidable, place it in lib/utils.dart (or the relevant platform module) so the primary API surface stays aligned with the generated schema.

Avoid manual shapes

Future<Map<String, dynamic>> fetchProducts(
  Map<String, dynamic> request,
) async {
  // ...
}

Future<void> finishTransaction(Map<String, dynamic> args) async {
  // ...
}

Hand-written maps or ad-hoc DTOs drift from the generated schema and are harder to maintain. Import lib/types.dart and wire the provided handler typedefs instead of recreating argument or result types.

Keep throwaway helpers local

• If a helper is only used inside a single method (less than three call sites), prefer declaring it inside that method instead of adding private class-level or top-level functions. This keeps utility clutter down and makes intent clearer when reading the code.