Help converting error types about fpdart

[SandroMaglione]

Hi @berbsd

How is ServiceError.mapError defined?

mapLeft((error) => ServiceError.mapError(error)) should convert ApiError to ServiceError for this to work, for example:

class ServiceError {
  ServiceError();
  factory ServiceError.mapError(ApiError error) => ServiceError();
}

The second ServiceError.mapError inside tryCatch cannot have the same signature, since the error in tryCatch gives you Object + StackTrace instead of ApiError.

If for example you refactor like below it compiles:

typedef URI = String;

class ServiceError {
  ServiceError();
  factory ServiceError.mapError(ApiError error) => ServiceError();
}

class ApiError {}

TaskEither<ApiError, String> getClient = TaskEither.of("");
TaskEither<ServiceError, String> apiCall(URI uri) {
  return getClient
      .mapLeft(
        (error) => ServiceError.mapError(error),
      )
      .flatMap(
        (client) => TaskEither.tryCatch(
          () async => client + "",
          (_, __) => ServiceError(),
        ),
      );
}

Let me know if you have any question