Allow passing HandlerFunction to run directly

Author: Ugzuzg

src/Common/index.ts

@@ -78,3 +78,7 @@ export type HandlerFunction = (
   data: IEnvironmentData & IHeaderData,
   callback: CallbackFunction
 ) => PromiseLike<unknown> | unknown;
+
+export function isHandlerFunction(value: any): value is HandlerFunction {
+  return typeof value === 'function';
+}

src/index.ts

@@ -8,7 +8,7 @@
 
 "use strict";
 
-import { HandlerFunction } from "./Common";
+import { HandlerFunction, isHandlerFunction } from "./Common";
 import * as Errors from "./Errors";
 import RuntimeClient from "./RuntimeClient";
 import Runtime from "./Runtime";
@@ -18,7 +18,7 @@ import * as UserFunction from "./utils/UserFunction";
 
 LogPatch.patchConsole();
 
-export function run(appRoot: string, handler: string): void {
+export function run(appRoot: string, handler: string | HandlerFunction): void {
   if (!process.env.AWS_LAMBDA_RUNTIME_API) {
     throw new Error("Missing Runtime API Server configuration.");
   }
@@ -50,7 +50,7 @@ export function run(appRoot: string, handler: string): void {
   BeforeExitListener.reset();
   process.on("beforeExit", BeforeExitListener.invoke);
 
-  const handlerFunc = UserFunction.load(appRoot, handler) as HandlerFunction;
+  const handlerFunc = isHandlerFunction(handler) ? handler : UserFunction.load(appRoot, handler) as HandlerFunction;
   const runtime = new Runtime(client, handlerFunc, errorCallbacks);
 
   runtime.scheduleIteration();