Function act

packages/internal-test-utils/internalAct.js:43–196

(scope: () => Thenable<T>)

}

export async function act<T>(scope: () => Thenable<T>): Thenable<T> {
  if (Scheduler.unstable_flushUntilNextPaint === undefined) {
    throw Error(
      'This version of `act` requires a special mock build of Scheduler.',
    );
  }

  const actualYields = Scheduler.unstable_clearLog();
  if (actualYields.length !== 0) {
    const error = Error(
      'Log of yielded values is not empty. Call assertLog first.\n\n' +
        `Received:\n${diff('', actualYields.join('\n'), {
          omitAnnotationLines: true,
        })}`,
    );
    Error.captureStackTrace(error, act);
    throw error;
  }

  // We require every `act` call to assert console logs
  // with one of the assertion helpers. Fails if not empty.
  assertConsoleLogsCleared();

  // $FlowFixMe[cannot-resolve-name]: Flow doesn't know about global Jest object
  if (!jest.isMockFunction(setTimeout)) {
    throw Error(
      "This version of `act` requires Jest's timer mocks " +
        '(i.e. jest.useFakeTimers).',
    );
  }

  const previousIsActEnvironment = global.IS_REACT_ACT_ENVIRONMENT;
  const previousActingUpdatesScopeDepth = actingUpdatesScopeDepth;
  actingUpdatesScopeDepth++;
  if (actingUpdatesScopeDepth === 1) {
    // Because this is not the "real" `act`, we set this to `false` so React
    // knows not to fire `act` warnings.
    global.IS_REACT_ACT_ENVIRONMENT = false;
  }

  // Create the error object before doing any async work, to get a better
  // stack trace.
  const error = new Error();
  Error.captureStackTrace(error, act);

  // Call the provided scope function after an async gap. This is an extra
  // precaution to ensure that our tests do not accidentally rely on the act
  // scope adding work to the queue synchronously. We don't do this in the
  // public version of `act`, though we maybe should in the future.
  await waitForMicrotasks();

  const errorHandlerDOM = function (event: ErrorEvent) {
    // Prevent logs from reprinting this error.
    event.preventDefault();
    thrownErrors.push(event.error);
  };
  const errorHandlerNode = function (err: mixed) {
    thrownErrors.push(err);