function()

in packages/expect/src/spyMatchers.ts [875:1004]

• 107 lines of code
• 24 McCabe index (conditional complexity)

  function (
    this: MatcherState,
    received: any,
    nth: number,
    ...expected: Array<unknown>
  ): SyncExpectationResult {
    const expectedArgument = 'n';
    const options: MatcherHintOptions = {
      expectedColor: (arg: string) => arg,
      isNot: this.isNot,
      promise: this.promise,
      secondArgument: '...expected',
    };
    ensureMockOrSpy(received, matcherName, expectedArgument, options);

    if (!Number.isSafeInteger(nth) || nth < 1) {
      throw new Error(
        matcherErrorMessage(
          matcherHint(matcherName, undefined, expectedArgument, options),
          `${expectedArgument} must be a positive integer`,
          printWithType(expectedArgument, nth, stringify),
        ),
      );
    }

    const receivedIsSpy = isSpy(received);
    const receivedName = receivedIsSpy ? 'spy' : received.getMockName();

    const calls = receivedIsSpy
      ? received.calls.all().map((x: any) => x.args)
      : received.mock.calls;
    const length = calls.length;
    const iNth = nth - 1;

    const pass = iNth < length && isEqualCall(expected, calls[iNth]);

    const message = pass
      ? () => {
          // Display preceding and following calls,
          // in case assertions fails because index is off by one.
          const indexedCalls: Array<IndexedCall> = [];
          if (iNth - 1 >= 0) {
            indexedCalls.push([iNth - 1, calls[iNth - 1]]);
          }
          indexedCalls.push([iNth, calls[iNth]]);
          if (iNth + 1 < length) {
            indexedCalls.push([iNth + 1, calls[iNth + 1]]);
          }

          return (
            // eslint-disable-next-line prefer-template
            matcherHint(matcherName, receivedName, expectedArgument, options) +
            '\n\n' +
            `n: ${nth}\n` +
            `Expected: not ${printExpectedArgs(expected)}\n` +
            (calls.length === 1 && stringify(calls[0]) === stringify(expected)
              ? ''
              : printReceivedCallsNegative(
                  expected,
                  indexedCalls,
                  calls.length === 1,
                  iNth,
                )) +
            `\nNumber of calls: ${printReceived(calls.length)}`
          );
        }
      : () => {
          // Display preceding and following calls:
          // * nearest call that is equal to expected args
          // * otherwise, adjacent call
          // in case assertions fails because of index, especially off by one.
          const indexedCalls: Array<IndexedCall> = [];
          if (iNth < length) {
            if (iNth - 1 >= 0) {
              let i = iNth - 1;
              // Is there a preceding call that is equal to expected args?
              while (i >= 0 && !isEqualCall(expected, calls[i])) {
                i -= 1;
              }
              if (i < 0) {
                i = iNth - 1; // otherwise, adjacent call
              }

              indexedCalls.push([i, calls[i]]);
            }
            indexedCalls.push([iNth, calls[iNth]]);
            if (iNth + 1 < length) {
              let i = iNth + 1;
              // Is there a following call that is equal to expected args?
              while (i < length && !isEqualCall(expected, calls[i])) {
                i += 1;
              }
              if (i >= length) {
                i = iNth + 1; // otherwise, adjacent call
              }

              indexedCalls.push([i, calls[i]]);
            }
          } else if (length > 0) {
            // The number of received calls is fewer than the expected number.
            let i = length - 1;
            // Is there a call that is equal to expected args?
            while (i >= 0 && !isEqualCall(expected, calls[i])) {
              i -= 1;
            }
            if (i < 0) {
              i = length - 1; // otherwise, last call
            }

            indexedCalls.push([i, calls[i]]);
          }

          return (
            // eslint-disable-next-line prefer-template
            matcherHint(matcherName, receivedName, expectedArgument, options) +
            '\n\n' +
            `n: ${nth}\n` +
            printExpectedReceivedCallsPositive(
              expected,
              indexedCalls,
              isExpand(this.expand),
              calls.length === 1,
              iNth,
            ) +
            `\nNumber of calls: ${printReceived(calls.length)}`
          );
        };

    return {message, pass};
  };