index.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

import type {
  Expect,
  ExpectationObject,
  AsyncExpectationResult,
  SyncExpectationResult,
  ExpectationResult,
  MatcherState,
  MatchersObject,
  RawMatcherFn,
  ThrowingMatcherFn,
  PromiseMatcherFn,
} from 'types/Matchers';

import * as matcherUtils from 'jest-matcher-utils';
import {iterableEquality, subsetEquality} from './utils';
import matchers from './matchers';
import spyMatchers from './spyMatchers';
import toThrowMatchers, {
  createMatcher as createThrowMatcher,
} from './toThrowMatchers';
import {equals} from './jasmineUtils';
import {
  any,
  anything,
  arrayContaining,
  arrayNotContaining,
  objectContaining,
  objectNotContaining,
  stringContaining,
  stringNotContaining,
  stringMatching,
  stringNotMatching,
} from './asymmetricMatchers';
import {
  INTERNAL_MATCHER_FLAG,
  getState,
  setState,
  getMatchers,
  setMatchers,
} from './jestMatchersObject';
import extractExpectedAssertionsErrors from './extractExpectedAssertionsErrors';

class JestAssertionError extends Error {
  matcherResult: any;
}

const isPromise = obj =>
  !!obj &&
  (typeof obj === 'object' || typeof obj === 'function') &&
  typeof obj.then === 'function';

const createToThrowErrorMatchingSnapshotMatcher = function(matcher) {
  return function(received: any, testNameOrInlineSnapshot?: string) {
    return matcher.apply(this, [received, testNameOrInlineSnapshot, true]);
  };
};

const getPromiseMatcher = (name, matcher) => {
  if (name === 'toThrow' || name === 'toThrowError') {
    return createThrowMatcher(name, true);
  } else if (
    name === 'toThrowErrorMatchingSnapshot' ||
    name === 'toThrowErrorMatchingInlineSnapshot'
  ) {
    return createToThrowErrorMatchingSnapshotMatcher(matcher);
  }

  return null;
};

const expect = (actual: any, ...rest): ExpectationObject => {
  if (rest.length !== 0) {
    throw new Error('Expect takes at most one argument.');
  }

  const allMatchers = getMatchers();
  const expectation = {
    not: {},
    rejects: {not: {}},
    resolves: {not: {}},
  };

  const err = new JestAssertionError();

  Object.keys(allMatchers).forEach(name => {
    const matcher = allMatchers[name];
    const promiseMatcher = getPromiseMatcher(name, matcher) || matcher;
    expectation[name] = makeThrowingMatcher(matcher, false, '', actual);
    expectation.not[name] = makeThrowingMatcher(matcher, true, '', actual);

    expectation.resolves[name] = makeResolveMatcher(
      name,
      promiseMatcher,
      false,
      actual,
      err,
    );
    expectation.resolves.not[name] = makeResolveMatcher(
      name,
      promiseMatcher,
      true,
      actual,
      err,
    );

    expectation.rejects[name] = makeRejectMatcher(
      name,
      promiseMatcher,
      false,
      actual,
      err,
    );
    expectation.rejects.not[name] = makeRejectMatcher(
      name,
      promiseMatcher,
      true,
      actual,
      err,
    );
  });

  return expectation;
};

const getMessage = message =>
  (message && message()) ||
  matcherUtils.RECEIVED_COLOR('No message was specified for this matcher.');

const makeResolveMatcher = (
  matcherName: string,
  matcher: RawMatcherFn,
  isNot: boolean,
  actual: Promise<any>,
  outerErr: JestAssertionError,
): PromiseMatcherFn => (...args) => {
  const options = {
    isNot,
    promise: 'resolves',
  };

  if (!isPromise(actual)) {
    throw new JestAssertionError(
      matcherUtils.matcherErrorMessage(
        matcherUtils.matcherHint(matcherName, undefined, '', options),
        `${matcherUtils.RECEIVED_COLOR('received')} value must be a promise`,
        matcherUtils.printWithType(
          'Received',
          actual,
          matcherUtils.printReceived,
        ),
      ),
    );
  }

  const innerErr = new JestAssertionError();

  return actual.then(
    result =>
      makeThrowingMatcher(matcher, isNot, 'resolves', result, innerErr).apply(
        null,
        args,
      ),
    reason => {
      outerErr.message =
        matcherUtils.matcherHint(matcherName, undefined, '', options) +
        '\n\n' +
        `Received promise rejected instead of resolved\n` +
        `Rejected to value: ${matcherUtils.printReceived(reason)}`;
      return Promise.reject(outerErr);
    },
  );
};

const makeRejectMatcher = (
  matcherName: string,
  matcher: RawMatcherFn,
  isNot: boolean,
  actual: Promise<any>,
  outerErr: JestAssertionError,
): PromiseMatcherFn => (...args) => {
  const options = {
    isNot,
    promise: 'rejects',
  };

  if (!isPromise(actual)) {
    throw new JestAssertionError(
      matcherUtils.matcherErrorMessage(
        matcherUtils.matcherHint(matcherName, undefined, '', options),
        `${matcherUtils.RECEIVED_COLOR('received')} value must be a promise`,
        matcherUtils.printWithType(
          'Received',
          actual,
          matcherUtils.printReceived,
        ),
      ),
    );
  }

  const innerErr = new JestAssertionError();

  return actual.then(
    result => {
      outerErr.message =
        matcherUtils.matcherHint(matcherName, undefined, '', options) +
        '\n\n' +
        `Received promise resolved instead of rejected\n` +
        `Resolved to value: ${matcherUtils.printReceived(result)}`;
      return Promise.reject(outerErr);
    },
    reason =>
      makeThrowingMatcher(matcher, isNot, 'rejects', reason, innerErr).apply(
        null,
        args,
      ),
  );
};

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

    const matcherContext: MatcherState = {
      // 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),
      ...getState(),
      equals,
      error: err,
      isNot,
      promise,
      utils,
    };

    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.
          // Guard for some environments (browsers) that do not support this feature.
          if (Error.captureStackTrace) {
            Error.captureStackTrace(error, throwingMatcher);
          }
        }
        // Passing the result of the matcher with the error so that a custom
        // reporter could access the actual and expected objects of the result
        // for example in order to display a custom visual diff
        error.matcherResult = result;

        if (throws) {
          throw error;
        } else {
          getState().suppressedErrors.push(error);
        }
      }
    };

    const handlError = (error: Error) => {
      if (
        matcher[INTERNAL_MATCHER_FLAG] === true &&
        !(error instanceof JestAssertionError) &&
        error.name !== 'PrettyFormatPluginError' &&
        // Guard for some environments (browsers) that do not support this feature.
        Error.captureStackTrace
      ) {
        // Try to remove this and deeper functions from the stack trace frame.
        Error.captureStackTrace(error, throwingMatcher);
      }
      throw error;
    };

    let potentialResult: ExpectationResult;

    try {
      potentialResult = matcher.apply(matcherContext, [actual].concat(args));

      if (isPromise((potentialResult: any))) {
        const asyncResult = ((potentialResult: any): AsyncExpectationResult);
        const asyncError = new JestAssertionError();
        if (Error.captureStackTrace) {
          Error.captureStackTrace(asyncError, throwingMatcher);
        }

        return asyncResult
          .then(aResult => processResult(aResult, asyncError))
          .catch(error => handlError(error));
      } else {
        const syncResult = ((potentialResult: any): SyncExpectationResult);

        return processResult(syncResult);
      }
    } catch (error) {
      return handlError(error);
    }
  };

expect.extend = (matchers: MatchersObject): void =>
  setMatchers(matchers, false, expect);

expect.anything = anything;
expect.any = any;

expect.not = {
  arrayContaining: arrayNotContaining,
  objectContaining: objectNotContaining,
  stringContaining: stringNotContaining,
  stringMatching: stringNotMatching,
};

expect.objectContaining = objectContaining;
expect.arrayContaining = arrayContaining;
expect.stringContaining = stringContaining;
expect.stringMatching = stringMatching;

const _validateResult = result => {
  if (
    typeof result !== 'object' ||
    typeof result.pass !== 'boolean' ||
    (result.message &&
      (typeof result.message !== 'string' &&
        typeof result.message !== 'function'))
  ) {
    throw new Error(
      'Unexpected return from a matcher function.\n' +
        'Matcher functions should ' +
        'return an object in the following format:\n' +
        '  {message?: string | function, pass: boolean}\n' +
        `'${matcherUtils.stringify(result)}' was returned`,
    );
  }
};

function assertions(expected: number) {
  const error = new Error();
  if (Error.captureStackTrace) {
    Error.captureStackTrace(error, assertions);
  }

  getState().expectedAssertionsNumber = expected;
  getState().expectedAssertionsNumberError = error;
}
function hasAssertions(...args) {
  const error = new Error();
  if (Error.captureStackTrace) {
    Error.captureStackTrace(error, hasAssertions);
  }

  matcherUtils.ensureNoExpected(args[0], '.hasAssertions');
  getState().isExpectingAssertions = true;
  getState().isExpectingAssertionsError = error;
}

// add default jest matchers
setMatchers(matchers, true, expect);
setMatchers(spyMatchers, true, expect);
setMatchers(toThrowMatchers, true, expect);

expect.addSnapshotSerializer = () => void 0;
expect.assertions = assertions;
expect.hasAssertions = hasAssertions;
expect.getState = getState;
expect.setState = setState;
expect.extractExpectedAssertionsErrors = extractExpectedAssertionsErrors;

module.exports = (expect: Expect);