feat(lambda-at-edge): add minifyHandlers input to minify handler code using Terser (#659)

Author: dphang

README.md

@@ -422,6 +422,7 @@ The fourth cache behaviour handles next API requests `api/*`.
 | publicDirectoryCache     | `boolean\|object` | `true`                                                                                                                     | Customize the `public`/`static` folder asset caching policy. Assigning an object with `value` and/or `test` lets you customize the caching policy and the types of files being cached. Assigning false disables caching                                                                                                                                                          |
 | useServerlessTraceTarget | `boolean`         | `false`                                                                                                                    | Use the experimental-serverless-trace target to build your next app. This is the same build target that Vercel Now uses. See this [RFC](https://github.com/vercel/next.js/pull/8246) for details.                                                                                                                                                                                |
 | logLambdaExecutionTimes  | `boolean`         | `false`                                                                                                                    | Logs to CloudWatch the default handler performance metrics.                                                                                                                                                                                                                                                                                                                      |
+| minifyHandlers           | `boolean`         | `false`                                                                                                                    | Use minified handlers to reduce code size.                                                                                                                                                                                                                                                                                                                                       |
 
 Custom inputs can be configured like this:
 

packages/libs/lambda-at-edge/package.json

@@ -43,6 +43,7 @@
     "@types/path-to-regexp": "^1.7.0",
     "rollup": "^2.26.6",
     "rollup-plugin-node-externals": "^2.2.0",
+    "rollup-plugin-terser": "^7.0.2",
     "rollup-plugin-typescript2": "^0.27.2",
     "ts-loader": "^7.0.5",
     "typescript": "^3.9.6"

packages/libs/lambda-at-edge/rollup.config.js

@@ -3,6 +3,7 @@ import typescript from "rollup-plugin-typescript2";
 import { nodeResolve } from "@rollup/plugin-node-resolve";
 import externals from "rollup-plugin-node-externals";
 import json from "@rollup/plugin-json";
+import { terser } from "rollup-plugin-terser";
 
 const LOCAL_EXTERNALS = [
   "./manifest.json",
@@ -11,10 +12,10 @@ const LOCAL_EXTERNALS = [
 ];
 const NPM_EXTERNALS = ["aws-lambda", "aws-sdk/clients/s3"];
 
-const generateConfig = (filename) => ({
-  input: `./src/${filename}.ts`,
+const generateConfig = (input) => ({
+  input: `./src/${input.filename}.ts`,
   output: {
-    file: `./dist/${filename}.js`,
+    file: `./dist/${input.filename}${input.minify ? ".min" : ""}.js`,
     format: "cjs"
   },
   plugins: [
@@ -26,10 +27,22 @@ const generateConfig = (filename) => ({
     nodeResolve(),
     typescript({
       tsconfig: "tsconfig.bundle.json"
-    })
+    }),
+    input.minify
+      ? terser({
+          compress: true,
+          mangle: true,
+          output: { comments: false } // Remove all comments, which is fine as the handler code is not distributed.
+        })
+      : undefined
   ],
   external: [...NPM_EXTERNALS, ...LOCAL_EXTERNALS],
   inlineDynamicImports: true
 });
 
-export default ["default-handler", "api-handler"].map(generateConfig);
+export default [
+  { filename: "default-handler", minify: false },
+  { filename: "default-handler", minify: true },
+  { filename: "api-handler", minify: false },
+  { filename: "api-handler", minify: true }
+].map(generateConfig);

packages/libs/lambda-at-edge/src/build.ts

@@ -29,6 +29,7 @@ type BuildOptions = {
   useServerlessTraceTarget?: boolean;
   logLambdaExecutionTimes?: boolean;
   domainRedirects?: { [key: string]: string };
+  minifyHandlers?: boolean;
 };
 
 const defaultBuildOptions = {
@@ -38,7 +39,8 @@ const defaultBuildOptions = {
   cmd: "./node_modules/.bin/next",
   useServerlessTraceTarget: false,
   logLambdaExecutionTimes: false,
-  domainRedirects: {}
+  domainRedirects: {},
+  minifyHandlers: false
 };
 
 class Builder {
@@ -179,6 +181,26 @@ class Builder {
     await fse.writeFile(destination, JSON.stringify(routesManifest));
   }
 
+  /**
+   * Process and copy handler code. This allows minifying it before copying to Lambda package.
+   * @param handlerType
+   * @param destination
+   * @param shouldMinify
+   */
+  async processAndCopyHandler(
+    handlerType: "api-handler" | "default-handler",
+    destination: string,
+    shouldMinify: boolean
+  ) {
+    const source = require.resolve(
+      `@sls-next/lambda-at-edge/dist/${handlerType}${
+        shouldMinify ? ".min" : ""
+      }.js`
+    );
+
+    await fse.copy(source, destination);
+  }
+
   async buildDefaultLambda(
     buildManifest: OriginRequestDefaultHandlerManifest
   ): Promise<void[]> {
@@ -223,9 +245,10 @@ class Builder {
 
     return Promise.all([
       ...copyTraces,
-      fse.copy(
-        require.resolve("@sls-next/lambda-at-edge/dist/default-handler.js"),
-        join(this.outputDir, DEFAULT_LAMBDA_CODE_DIR, "index.js")
+      this.processAndCopyHandler(
+        "default-handler",
+        join(this.outputDir, DEFAULT_LAMBDA_CODE_DIR, "index.js"),
+        !!this.buildOptions.minifyHandlers
       ),
       fse.writeJson(
         join(this.outputDir, DEFAULT_LAMBDA_CODE_DIR, "manifest.json"),
@@ -302,9 +325,10 @@ class Builder {
 
     return Promise.all([
       ...copyTraces,
-      fse.copy(
-        require.resolve("@sls-next/lambda-at-edge/dist/api-handler.js"),
-        join(this.outputDir, API_LAMBDA_CODE_DIR, "index.js")
+      this.processAndCopyHandler(
+        "api-handler",
+        join(this.outputDir, API_LAMBDA_CODE_DIR, "index.js"),
+        !!this.buildOptions.minifyHandlers
       ),
       fse.copy(
         join(this.serverlessDir, "pages/api"),
@@ -453,7 +477,7 @@ class Builder {
     }
   }
 
-  async build(debugMode: boolean): Promise<void> {
+  async build(debugMode?: boolean): Promise<void> {
     const { cmd, args, cwd, env, useServerlessTraceTarget } = Object.assign(
       defaultBuildOptions,
       this.buildOptions