function makeInvokeMethod()

in packages/runtime/runtime.js [244:320]
55 lines of code
16 McCabe index (conditional complexity)

  function makeInvokeMethod(innerFn, self, context) {
    var state = GenStateSuspendedStart;

    return function invoke(method, arg) {
      if (state === GenStateExecuting) {
        throw new Error("Generator is already running");
      }

      if (state === GenStateCompleted) {
        if (method === "throw") {
          throw arg;
        }

        // Be forgiving, per 25.3.3.3.3 of the spec:
        // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-generatorresume
        return doneResult();
      }

      context.method = method;
      context.arg = arg;

      while (true) {
        var delegate = context.delegate;
        if (delegate) {
          var delegateResult = maybeInvokeDelegate(delegate, context);
          if (delegateResult) {
            if (delegateResult === ContinueSentinel) continue;
            return delegateResult;
          }
        }

        if (context.method === "next") {
          // Setting context._sent for legacy support of Babel's
          // function.sent implementation.
          context.sent = context._sent = context.arg;

        } else if (context.method === "throw") {
          if (state === GenStateSuspendedStart) {
            state = GenStateCompleted;
            throw context.arg;
          }

          context.dispatchException(context.arg);

        } else if (context.method === "return") {
          context.abrupt("return", context.arg);
        }

        state = GenStateExecuting;

        var record = tryCatch(innerFn, self, context);
        if (record.type === "normal") {
          // If an exception is thrown from innerFn, we leave state ===
          // GenStateExecuting and loop back for another invocation.
          state = context.done
            ? GenStateCompleted
            : GenStateSuspendedYield;

          if (record.arg === ContinueSentinel) {
            continue;
          }

          return {
            value: record.arg,
            done: context.done
          };

        } else if (record.type === "throw") {
          state = GenStateCompleted;
          // Dispatch the exception by looping back around to the
          // context.dispatchException(context.arg) call above.
          context.method = "throw";
          context.arg = record.arg;
        }
      }
    };
  }