toMatch()

in packages/expect/src/matchers.ts [794:870]
71 lines of code
10 McCabe index (conditional complexity)

  toMatch(received: string, expected: string | RegExp) {
    const matcherName = 'toMatch';
    const options: MatcherHintOptions = {
      isNot: this.isNot,
      promise: this.promise,
    };

    if (typeof received !== 'string') {
      throw new Error(
        matcherErrorMessage(
          matcherHint(matcherName, undefined, undefined, options),
          `${RECEIVED_COLOR('received')} value must be a string`,
          printWithType('Received', received, printReceived),
        ),
      );
    }

    if (
      !(typeof expected === 'string') &&
      !(expected && typeof expected.test === 'function')
    ) {
      throw new Error(
        matcherErrorMessage(
          matcherHint(matcherName, undefined, undefined, options),
          `${EXPECTED_COLOR(
            'expected',
          )} value must be a string or regular expression`,
          printWithType('Expected', expected, printExpected),
        ),
      );
    }

    const pass =
      typeof expected === 'string'
        ? received.includes(expected)
        : new RegExp(expected).test(received);

    const message = pass
      ? () =>
          typeof expected === 'string'
            ? // eslint-disable-next-line prefer-template
              matcherHint(matcherName, undefined, undefined, options) +
              '\n\n' +
              `Expected substring: not ${printExpected(expected)}\n` +
              `Received string:        ${printReceivedStringContainExpectedSubstring(
                received,
                received.indexOf(expected),
                expected.length,
              )}`
            : // eslint-disable-next-line prefer-template
              matcherHint(matcherName, undefined, undefined, options) +
              '\n\n' +
              `Expected pattern: not ${printExpected(expected)}\n` +
              `Received string:      ${printReceivedStringContainExpectedResult(
                received,
                typeof expected.exec === 'function'
                  ? expected.exec(received)
                  : null,
              )}`
      : () => {
          const labelExpected = `Expected ${
            typeof expected === 'string' ? 'substring' : 'pattern'
          }`;
          const labelReceived = 'Received string';
          const printLabel = getLabelPrinter(labelExpected, labelReceived);

          return (
            // eslint-disable-next-line prefer-template
            matcherHint(matcherName, undefined, undefined, options) +
            '\n\n' +
            `${printLabel(labelExpected)}${printExpected(expected)}\n` +
            `${printLabel(labelReceived)}${printReceived(received)}`
          );
        };

    return {message, pass};
  },