fix: Hot reloading with chokidar & busting of the require cache. (#515)

* fix: Hot reloading with chokidar & delete require cache.

* chore: removed reformatting.

* Readme for the hot reloader for esbuild and typescript

* feat(hot reload): Hot reload for esbuild and typescript based serverless projects

* opted for not changing the default path.

* support for url based references in package json files.

Co-authored-by: Robb Lovell <[email protected]>
Co-authored-by: Matt Strom <[email protected]>

README.md

@@ -14,7 +14,7 @@ _serverless.yml_
 ```yaml
 service:
   name: edge-lambdas
-  
+
 plugins:
   - serverless-offline-edge-lambda
 
@@ -60,7 +60,7 @@ a configuration option `path` that it uses to resolve function handlers.
 ```yaml
 plugins:
   - serverless-plugin-typescript
-    
+
 custom:
   offlineEdgeLambda:
     path: '.build'
@@ -70,8 +70,40 @@ For usage with `serverless-webpack` and `serverless-bundle` the config is simila
 ```yaml
 plugins:
   - serverless-webpack # or serverless-bundle
-  
+
 custom:
   offlineEdgeLambda:
     path: './.webpack/service/'
 ```
+
+### Hot Reload Support
+
+Hot reload for serverless-esbuild and serverless-plugin-typescript are available with extra configuration.
+
+The watch/reload mechanism is available form serverless-webpack, but is disabled by default for esbuild and typescript.
+
+The flag "watchReload: true" will turn on the watcher so that typescript and esbuild solutions use the watcher to hot reload the handlers.
+The path to the built handlers must be specified for the watcher to work correctly.
+
+example:
+```yaml
+custom:
+  offlineEdgeLambda:
+    path: '.esbuild/service'
+    watchReload: true
+```
+
+Additional options can be used to modify the behavior of the file watcher and debounce logic (ignoreInitial, awaitWriteFinish, interval, debounce, and any other chokidar option).
+
+example:
+
+```yaml
+custom:
+  offlineEdgeLambda:
+    path: '.dist/service'
+    watchReload: true
+    ignoreInitial: true
+    awaitWriteFinish: true
+    interval: 500,
+    debounce: 750
+```

package.json

@@ -17,7 +17,7 @@
     "release": "semantic-release --no-ci",
     "release:dry-run": "semantic-release --no-ci --dry-run",
     "snyk-protect": "snyk protect",
-    "prepare": "npm run snyk-protect"
+    "prepare": "npm run snyk-protect && npm run build"
   },
   "config": {
     "commitizen": {
@@ -49,6 +49,7 @@
   ],
   "dependencies": {
     "body-parser": "^1.20.0",
+    "chokidar": "^3.5.3",
     "connect": "^3.7.0",
     "cookie-parser": "^1.4.6",
     "flat-cache": "^3.0.4",

src/behavior-router.ts

@@ -2,13 +2,14 @@ import { Context } from 'aws-lambda';
 import bodyParser from 'body-parser';
 import connect, { HandleFunction } from 'connect';
 import cookieParser from 'cookie-parser';
+import * as chokidar from 'chokidar';
 import * as fs from 'fs-extra';
 import { createServer, Server, IncomingMessage, ServerResponse } from 'http';
 import { StatusCodes } from 'http-status-codes';
 import * as os from 'os';
 import * as path from 'path';
 import { URL } from 'url';
-
+import { debounce } from './utils/debounce';
 import { HttpError, InternalServerError } from './errors/http';
 import { FunctionSet } from './function-set';
 import { asyncMiddleware, cloudfrontPost } from './middlewares';
@@ -62,6 +63,25 @@ export class BehaviorRouter {
 
 		this.origins = this.configureOrigins();
 		this.cacheService = new CacheService(this.cacheDir);
+
+		if (this.serverless.service.custom.offlineEdgeLambda.watchReload) {
+			this.watchFiles(path.join(this.path, '**/*'), {
+				ignoreInitial: true,
+				awaitWriteFinish: true,
+				interval: 500,
+				debounce: 750,
+				...options,
+			});
+		}
+	}
+
+	watchFiles(pattern: any, options: any) {
+		const watcher = chokidar.watch(pattern, options);
+		watcher.on('all', debounce(async (eventName, srcPath) => {
+			console.log('Lambda files changed, syncing...');
+			await this.extractBehaviors();
+			console.log('Lambda files synced');
+		}, options.debounce, true));
 	}
 
 	match(req: IncomingMessage): FunctionSet | null {

src/utils/debounce.ts

@@ -0,0 +1,22 @@
+export const debounce =
+	function (func: { (eventName: any, srcPath: any): Promise<void>; apply?: any; }, threshold: number, execAsap: boolean) {
+	let timeout: any;
+	return function debounced(this: any) {
+		const obj = this;
+		const args = arguments;
+
+		function delayed() {
+			if (!execAsap) {
+				func.apply(obj, args);
+			}
+			timeout = undefined;
+		}
+
+		if (timeout) {
+			clearTimeout(timeout);
+		} else if (execAsap) {
+			func.apply(obj, args);
+		}
+		timeout = setTimeout(delayed, threshold || 100);
+	};
+};

src/utils/load-module.ts

@@ -1,5 +1,5 @@
 import { resolve } from 'path';
-import {clearModule} from './clear-module';
+import { clearModule } from './clear-module';
 
 export class ModuleLoader {
 	protected loadedModules: string[] = [];
@@ -15,6 +15,7 @@ export class ModuleLoader {
 		const [, modulePath, functionName] = match;
 		const absPath = resolve(modulePath);
 
+		delete require.cache[require.resolve(absPath)];
 		const module = await import(absPath);
 
 		this.loadedModules.push(absPath);