Function toContain

packages/playwright/src/matchers/expectLibrary.ts:914–995

(received: ContainIterable | string, expected: unknown)

  },

  toContain(received: ContainIterable | string, expected: unknown) {
    const matcherName = 'toContain';
    const isNot = this.isNot;
    const options: MatcherHintOptions = { comment: 'indexOf', isNot, promise: this.promise };

    if (received === null || received === undefined) {
      throw new Error(
          matcherErrorMessage(
              matcherHint(matcherName, undefined, undefined, options),
              `${RECEIVED_COLOR('received')} value must not be null nor undefined`,
              printWithType('Received', received, printReceived),
          ),
      );
    }

    if (typeof received === 'string') {
      const wrongTypeErrorMessage = `${EXPECTED_COLOR('expected')} value must be a string if ${RECEIVED_COLOR('received')} value is a string`;

      if (typeof expected !== 'string') {
        throw new TypeError(
            matcherErrorMessage(
                matcherHint(matcherName, received, String(expected), options),
                wrongTypeErrorMessage,
                printWithType('Expected', expected, printExpected) +
              '\n' +
              printWithType('Received', received, printReceived),
            ),
        );
      }

      const index = received.indexOf(String(expected));
      const pass = index !== -1;

      const message = () => {
        const labelExpected = `Expected ${typeof expected === 'string' ? 'substring' : 'value'}`;
        const labelReceived = 'Received string';
        const printLabel = getLabelPrinter(labelExpected, labelReceived);

        return (
          matcherHint(matcherName, undefined, undefined, options) +
          '\n\n' +
          `${printLabel(labelExpected)}${isNot ? 'not ' : ''}${printExpected(expected)}\n` +
          `${printLabel(labelReceived)}${isNot ? '    ' : ''}${
            isNot
              ? printReceivedStringContainExpectedSubstring(received, index, String(expected).length)
              : printReceived(received)
          }`
        );
      };

      return { message, pass };
    }

    const indexable = [...received];
    const index = indexable.indexOf(expected);
    const pass = index !== -1;

    const message = () => {