function commitMutation()

in packages/relay-runtime/mutations/commitMutation.js [72:157]
85 lines of code
12 McCabe index (conditional complexity)

function commitMutation<TMutation: MutationParameters>(
  environment: IEnvironment,
  config: MutationConfig<TMutation>,
): Disposable {
  invariant(
    isRelayModernEnvironment(environment),
    'commitMutation: expected `environment` to be an instance of ' +
      '`RelayModernEnvironment`.',
  );
  const mutation = getRequest(config.mutation);
  if (mutation.params.operationKind !== 'mutation') {
    throw new Error('commitMutation: Expected mutation operation');
  }
  if (mutation.kind !== 'Request') {
    throw new Error('commitMutation: Expected mutation to be of type request');
  }
  let {optimisticResponse, optimisticUpdater, updater} = config;
  const {configs, cacheConfig, onError, onUnsubscribe, variables, uploadables} =
    config;
  const operation = createOperationDescriptor(
    mutation,
    variables,
    cacheConfig,
    generateUniqueClientID(),
  );
  // TODO: remove this check after we fix flow.
  if (typeof optimisticResponse === 'function') {
    optimisticResponse = optimisticResponse();
    warning(
      false,
      'commitMutation: Expected `optimisticResponse` to be an object, ' +
        'received a function.',
    );
  }
  if (__DEV__) {
    if (optimisticResponse instanceof Object) {
      validateMutation(optimisticResponse, mutation, variables);
    }
  }
  if (configs) {
    ({optimisticUpdater, updater} = RelayDeclarativeMutationConfig.convert(
      configs,
      mutation,
      optimisticUpdater,
      updater,
    ));
  }
  const errors = [];
  const subscription = environment
    .executeMutation({
      operation,
      optimisticResponse,
      optimisticUpdater,
      updater,
      uploadables,
    })
    .subscribe({
      next: payload => {
        if (Array.isArray(payload)) {
          payload.forEach(item => {
            if (item.errors) {
              errors.push(...item.errors);
            }
          });
        } else {
          if (payload.errors) {
            errors.push(...payload.errors);
          }
        }
        config.onNext?.();
      },
      complete: () => {
        const {onCompleted} = config;
        if (onCompleted) {
          const snapshot = environment.lookup(operation.fragment);
          onCompleted(
            (snapshot.data: $FlowFixMe),
            errors.length !== 0 ? errors : null,
          );
        }
      },
      error: onError,
      unsubscribe: onUnsubscribe,
    });
  return {dispose: subscription.unsubscribe};
}