function maybeInvokeDelegate()

in packages/runtime/runtime.js [326:403]

• 46 lines of code
• 9 McCabe index (conditional complexity)

  function maybeInvokeDelegate(delegate, context) {
    var method = delegate.iterator[context.method];
    if (method === undefined) {
      // A .throw or .return when the delegate iterator has no .throw
      // method always terminates the yield* loop.
      context.delegate = null;

      if (context.method === "throw") {
        // Note: ["return"] must be used for ES3 parsing compatibility.
        if (delegate.iterator["return"]) {
          // If the delegate iterator has a return method, give it a
          // chance to clean up.
          context.method = "return";
          context.arg = undefined;
          maybeInvokeDelegate(delegate, context);

          if (context.method === "throw") {
            // If maybeInvokeDelegate(context) changed context.method from
            // "return" to "throw", let that override the TypeError below.
            return ContinueSentinel;
          }
        }

        context.method = "throw";
        context.arg = new TypeError(
          "The iterator does not provide a 'throw' method");
      }

      return ContinueSentinel;
    }

    var record = tryCatch(method, delegate.iterator, context.arg);

    if (record.type === "throw") {
      context.method = "throw";
      context.arg = record.arg;
      context.delegate = null;
      return ContinueSentinel;
    }

    var info = record.arg;

    if (! info) {
      context.method = "throw";
      context.arg = new TypeError("iterator result is not an object");
      context.delegate = null;
      return ContinueSentinel;
    }

    if (info.done) {
      // Assign the result of the finished delegate to the temporary
      // variable specified by delegate.resultName (see delegateYield).
      context[delegate.resultName] = info.value;

      // Resume execution at the desired location (see delegateYield).
      context.next = delegate.nextLoc;

      // If context.method was "throw" but the delegate handled the
      // exception, let the outer generator proceed normally. If
      // context.method was "next", forget context.arg since it has been
      // "consumed" by the delegate iterator. If context.method was
      // "return", allow the original .return call to continue in the
      // outer generator.
      if (context.method !== "return") {
        context.method = "next";
        context.arg = undefined;
      }

    } else {
      // Re-yield the result returned by the delegate method.
      return info;
    }

    // The delegate iterator is finished, so forget it and continue with
    // the outer generator.
    context.delegate = null;
    return ContinueSentinel;
  }