Function makeThrowingMatcher

packages/expect/src/index.ts:275–395

(
  matcher: RawMatcherFn,
  isNot: boolean,
  promise: string,
  actual: any,
  err?: JestAssertionError,
)

  };

const makeThrowingMatcher = (
  matcher: RawMatcherFn,
  isNot: boolean,
  promise: string,
  actual: any,
  err?: JestAssertionError,
): ThrowingMatcherFn =>
  function throwingMatcher(...args): any {
    let throws = true;
    const utils: MatcherUtils['utils'] = {
      ...matcherUtils,
      iterableEquality,
      subsetEquality,
    };

    const matcherUtilsThing: MatcherUtils = {
      customTesters: getCustomEqualityTesters(),
      // When throws is disabled, the matcher will not throw errors during test
      // execution but instead add them to the global matcher state. If a
      // matcher throws, test execution is normally stopped immediately. The
      // snapshot matcher uses it because we want to log all snapshot
      // failures in a test.
      dontThrow: () => (throws = false),
      equals,
      utils,
    };

    const matcherContext: MatcherContext = {
      ...getState<MatcherState>(),
      ...matcherUtilsThing,
      error: err,
      isNot,
      promise,
    };

    const processResult = (
      result: SyncExpectationResult,
      asyncError?: JestAssertionError,
    ) => {
      _validateResult(result);

      getState().assertionCalls++;

      if ((result.pass && isNot) || (!result.pass && !isNot)) {
        // XOR
        const message = getMessage(result.message);
        let error;

        if (err) {
          error = err;
          error.message = message;
        } else if (asyncError) {
          error = asyncError;
          error.message = message;
        } else {
          error = new JestAssertionError(message);

          // Try to remove this function from the stack trace frame.