feat(terser): parallel execution (#1341)

* feat(terser): parallel execution

* fix(terser): exit process on promise rejection of worker

* feat(terser): add woker-pool support

* docs(terser): updated docs

* fix(terser): worker count decrementation

* style(terser): removed unnecessary Promise.resolve wrapping

* docs(terser): enhanced options section

* docs(terser): fix typo

packages/terser/README.md

@@ -9,11 +9,11 @@
 
 # @rollup/plugin-terser
 
-🍣 A Rollup plugin to generate a minified output bundle.
+🍣 A Rollup plugin to generate a minified bundle with terser.
 
 ## Requirements
 
-This plugin requires an [LTS](https://github.com/nodejs/Release) Node version (v14.0.0+) and Rollup v1.20.0+.
+This plugin requires an [LTS](https://github.com/nodejs/Release) Node version (v14.0.0+) and Rollup v2.0+.
 
 ## Install
 
@@ -27,7 +27,7 @@ npm install @rollup/plugin-terser --save-dev
 
 Create a `rollup.config.js` [configuration file](https://www.rollupjs.org/guide/en/#configuration-files) and import the plugin:
 
-```js
+```typescript
 import terser from '@rollup/plugin-terser';
 
 export default {
@@ -47,13 +47,34 @@ Then call `rollup` either via the [CLI](https://www.rollupjs.org/guide/en/#comma
 The plugin accepts a terser [Options](https://github.com/terser/terser#minify-options) object as input parameter,
 to modify the default behaviour.
 
+In addition to the `terser` options, it is also possible to provide the following options:
+
+### `maxWorkers`
+
+Type: `Number`<br>
+Default: `undefined`
+
+Instructs the plugin to use a specific amount of cpu threads.
+
+```typescript
+import terser from '@rollup/plugin-terser';
+
+export default {
+  input: 'src/index.js',
+  output: {
+    dir: 'output',
+    format: 'cjs'
+  },
+  plugins: [
+    terser({
+      maxWorkers: 4
+    })
+  ]
+};
+```
+
 ## Meta
 
 [CONTRIBUTING](/.github/CONTRIBUTING.md)
 
 [LICENSE (MIT)](/LICENSE)
-
-## Credits
-
-This package was originally developed by [https://github.com/TrySound](TrySound) but is not
-maintained anymore.

packages/terser/package.json

@@ -61,9 +61,12 @@
     }
   },
   "dependencies": {
+    "serialize-javascript": "^6.0.0",
+    "smob": "^0.0.6",
     "terser": "^5.15.1"
   },
   "devDependencies": {
+    "@types/serialize-javascript": "^5.0.2",
     "rollup": "^3.0.0-7",
     "typescript": "^4.8.3"
   },

packages/terser/src/index.ts

@@ -1,25 +1,8 @@
-import type { NormalizedOutputOptions, RenderedChunk } from 'rollup';
-import type { MinifyOptions } from 'terser';
-import { minify } from 'terser';
+import { runWorker } from './worker';
+import terser from './module';
 
-export default function terser(options?: MinifyOptions) {
-  return {
-    name: 'terser',
+runWorker();
 
-    async renderChunk(code: string, chunk: RenderedChunk, outputOptions: NormalizedOutputOptions) {
-      const defaultOptions: MinifyOptions = {
-        sourceMap: outputOptions.sourcemap === true || typeof outputOptions.sourcemap === 'string'
-      };
+export * from './type';
 
-      if (outputOptions.format === 'es') {
-        defaultOptions.module = true;
-      }
-
-      if (outputOptions.format === 'cjs') {
-        defaultOptions.toplevel = true;
-      }
-
-      return minify(code, { ...defaultOptions, ...(options || {}) });
-    }
-  };
-}
+export default terser;

packages/terser/src/module.ts

@@ -0,0 +1,72 @@
+import type { NormalizedOutputOptions, RenderedChunk } from 'rollup';
+import { hasOwnProperty, isObject, merge } from 'smob';
+
+import type { Options } from './type';
+import { WorkerPool } from './worker-pool';
+
+export default function terser(options: Options = {}) {
+  const workerPool = new WorkerPool({
+    filePath: __filename,
+    maxWorkers: options.maxWorkers
+  });
+
+  return {
+    name: 'terser',
+
+    async renderChunk(code: string, chunk: RenderedChunk, outputOptions: NormalizedOutputOptions) {
+      const defaultOptions: Options = {
+        sourceMap: outputOptions.sourcemap === true || typeof outputOptions.sourcemap === 'string'
+      };
+
+      if (outputOptions.format === 'es') {
+        defaultOptions.module = true;
+      }
+
+      if (outputOptions.format === 'cjs') {
+        defaultOptions.toplevel = true;
+      }
+
+      try {
+        const { code: result, nameCache } = await workerPool.addAsync({
+          code,
+          options: merge({}, options || {}, defaultOptions)
+        });
+
+        if (options.nameCache && nameCache) {
+          let vars: Record<string, any> = {
+            props: {}
+          };
+
+          if (hasOwnProperty(options.nameCache, 'vars') && isObject(options.nameCache.vars)) {
+            vars = merge({}, options.nameCache.vars || {}, vars);
+          }
+
+          if (hasOwnProperty(nameCache, 'vars') && isObject(nameCache.vars)) {
+            vars = merge({}, nameCache.vars, vars);
+          }
+
+          // eslint-disable-next-line no-param-reassign
+          options.nameCache.vars = vars;
+
+          let props: Record<string, any> = {};
+
+          if (hasOwnProperty(options.nameCache, 'props') && isObject(options.nameCache.props)) {
+            // eslint-disable-next-line prefer-destructuring
+            props = options.nameCache.props;
+          }
+
+          if (hasOwnProperty(nameCache, 'props') && isObject(nameCache.props)) {
+            props = merge({}, nameCache.props, props);
+          }
+
+          // eslint-disable-next-line no-param-reassign
+          options.nameCache.props = props;
+        }
+
+        return result;
+      } catch (e) {
+        return Promise.reject(e);
+      }
+    }
+  };
+}

packages/terser/src/type.ts

@@ -0,0 +1,33 @@
+import type { MinifyOptions } from 'terser';
+
+export interface Options extends MinifyOptions {
+  nameCache?: Record<string, any>;
+  maxWorkers?: number;
+}
+
+export interface WorkerContext {
+  code: string;
+  options: Options;
+}
+
+export type WorkerCallback = (err: Error | null, output?: WorkerOutput) => void;
+
+export interface WorkerContextSerialized {
+  code: string;
+  options: string;
+}
+
+export interface WorkerOutput {
+  code: string;
+  nameCache?: Options['nameCache'];
+}
+
+export interface WorkerPoolOptions {
+  filePath: string;
+  maxWorkers?: number;
+}
+
+export interface WorkerPoolTask {
+  context: WorkerContext;
+  cb: WorkerCallback;
+}

packages/terser/src/worker-pool.ts

@@ -0,0 +1,117 @@
+import { Worker } from 'worker_threads';
+import { cpus } from 'os';
+import { EventEmitter } from 'events';
+
+import serializeJavascript from 'serialize-javascript';
+
+import type {
+  WorkerCallback,
+  WorkerContext,
+  WorkerOutput,
+  WorkerPoolOptions,
+  WorkerPoolTask
+} from './type';
+
+const symbol = Symbol.for('FreeWoker');
+
+export class WorkerPool extends EventEmitter {
+  protected maxInstances: number;
+
+  protected filePath: string;
+
+  protected tasks: WorkerPoolTask[] = [];
+
+  protected workers = 0;
+
+  constructor(options: WorkerPoolOptions) {
+    super();
+
+    this.maxInstances = options.maxWorkers || cpus().length;
+    this.filePath = options.filePath;
+
+    this.on(symbol, () => {
+      if (this.tasks.length > 0) {
+        this.run();
+      }
+    });
+  }
+
+  add(context: WorkerContext, cb: WorkerCallback) {
+    this.tasks.push({
+      context,
+      cb
+    });
+
+    if (this.workers >= this.maxInstances) {
+      return;
+    }
+
+    this.run();
+  }
+
+  async addAsync(context: WorkerContext): Promise<WorkerOutput> {
+    return new Promise((resolve, reject) => {
+      this.add(context, (err, output) => {
+        if (err) {
+          reject(err);
+          return;
+        }
+
+        if (!output) {
+          reject(new Error('The output is empty'));
+          return;
+        }
+
+        resolve(output);
+      });
+    });
+  }
+
+  private run() {
+    if (this.tasks.length === 0) {
+      return;
+    }
+
+    const task = this.tasks.shift();
+
+    if (typeof task === 'undefined') {
+      return;
+    }
+
+    this.workers += 1;
+
+    let called = false;
+    const callCallback = (err: Error | null, output?: WorkerOutput) => {
+      if (called) {
+        return;
+      }
+      called = true;
+
+      this.workers -= 1;
+
+      task.cb(err, output);
+      this.emit(symbol);
+    };
+
+    const worker = new Worker(this.filePath, {
+      workerData: {
+        code: task.context.code,
+        options: serializeJavascript(task.context.options)
+      }
+    });
+
+    worker.on('message', (data) => {
+      callCallback(null, data);
+    });
+
+    worker.on('error', (err) => {
+      callCallback(err);
+    });
+
+    worker.on('exit', (code) => {
+      if (code !== 0) {
+        callCallback(new Error(`Minify worker stopped with exit code ${code}`));
+      }
+    });
+  }
+}

packages/terser/src/worker.ts

@@ -0,0 +1,47 @@
+import process from 'process';
+import { isMainThread, parentPort, workerData } from 'worker_threads';
+
+import { hasOwnProperty, isObject } from 'smob';
+
+import { minify } from 'terser';
+
+import type { WorkerContextSerialized, WorkerOutput } from './type';
+
+/**
+ * Duck typing worker context.
+ *
+ * @param input
+ */
+function isWorkerContextSerialized(input: unknown): input is WorkerContextSerialized {
+  return (
+    isObject(input) &&
+    hasOwnProperty(input, 'code') &&
+    typeof input.code === 'string' &&
+    hasOwnProperty(input, 'options') &&
+    typeof input.options === 'string'
+  );
+}
+
+export async function runWorker() {
+  if (isMainThread || !parentPort || !isWorkerContextSerialized(workerData)) {
+    return;
+  }
+
+  try {
+    // eslint-disable-next-line no-eval
+    const eval2 = eval;
+
+    const options = eval2(`(${workerData.options})`);
+
+    const result = await minify(workerData.code, options);
+
+    const output: WorkerOutput = {
+      code: result.code || workerData.code,
+      nameCache: options.nameCache
+    };
+
+    parentPort.postMessage(output);
+  } catch (e) {
+    process.exit(1);
+  }
+}

packages/terser/test/test.js

@@ -107,7 +107,7 @@ test.serial('throw error on terser fail', async (t) => {
     await bundle.generate({ format: 'esm' });
     t.falsy(true);
   } catch (error) {
-    t.is(error.toString(), 'SyntaxError: Name expected');
+    t.is(error.toString(), 'Error: Minify worker stopped with exit code 1');
   }
 });
 
@@ -127,7 +127,7 @@ test.serial('throw error on terser fail with multiple outputs', async (t) => {
     await Promise.all([bundle.generate({ format: 'cjs' }), bundle.generate({ format: 'esm' })]);
     t.falsy(true);
   } catch (error) {
-    t.is(error.toString(), 'SyntaxError: Name expected');
+    t.is(error.toString(), 'Error: Minify worker stopped with exit code 1');
   }
 });