Function wrapUserFunction

src/function_wrappers.ts:208–232

(
  userFunction: HandlerFunction<T>,
  signatureType: SignatureType,
)

 * @return An Express handler function that invokes the user function.
 */
export const wrapUserFunction = <T = unknown>(
  userFunction: HandlerFunction<T>,
  signatureType: SignatureType,
): RequestHandler => {
  switch (signatureType) {
    case 'http':
      return wrapHttpFunction(userFunction as HttpFunction);
    case 'event':
      // Callback style if user function has more than 2 arguments.
      if (userFunction instanceof Function && userFunction!.length > 2) {
        return wrapEventFunctionWithCallback(
          userFunction as EventFunctionWithCallback,
        );
      }
      return wrapEventFunction(userFunction as EventFunction);
    case 'cloudevent':
      if (userFunction instanceof Function && userFunction!.length > 1) {
        // Callback style if user function has more than 1 argument.
        return wrapCloudEventFunctionWithCallback(
          userFunction as CloudEventFunctionWithCallback,
        );
      }
      return wrapCloudEventFunction(userFunction as CloudEventFunction);
  }
};