fix: parallel in multi compilation mode

src/index.js

@@ -428,7 +428,7 @@ class TerserPlugin {
     yield task;
   }
 
-  async runTasks() {
+  async runTasks(assetNames) {
     const availableNumberOfCores = TerserPlugin.getAvailableNumberOfCores(
       this.options.parallel
     );
@@ -438,10 +438,7 @@ class TerserPlugin {
 
     if (availableNumberOfCores > 0) {
       // Do not create unnecessary workers when the number of files is less than the available cores, it saves memory
-      const numWorkers = Math.min(
-        this.assetNames.length,
-        availableNumberOfCores
-      );
+      const numWorkers = Math.min(assetNames.length, availableNumberOfCores);
 
       concurrency = numWorkers;
 
@@ -468,7 +465,7 @@ class TerserPlugin {
     const limit = pLimit(concurrency);
     const scheduledTasks = [];
 
-    for (const assetName of this.assetNames) {
+    for (const assetName of assetNames) {
       const enqueue = async (task) => {
         let taskResult;
 
@@ -565,8 +562,10 @@ class TerserPlugin {
         this.options
       );
 
+      let assetNames;
+
       if (TerserPlugin.isWebpack4()) {
-        this.assetNames = []
+        assetNames = []
           .concat(Array.from(compilation.additionalChunkAssets || []))
           .concat(
             Array.from(chunksOrAssets).reduce(
@@ -576,12 +575,12 @@ class TerserPlugin {
           )
           .filter((file) => matchObject(file));
       } else {
-        this.assetNames = []
+        assetNames = []
           .concat(Object.keys(chunksOrAssets))
           .filter((file) => matchObject(file));
       }
 
-      if (this.assetNames.length === 0) {
+      if (assetNames.length === 0) {
         return Promise.resolve();
       }
 
@@ -604,7 +603,7 @@ class TerserPlugin {
         allExtractedComments
       );
 
-      await this.runTasks();
+      await this.runTasks(assetNames);
 
       Object.keys(allExtractedComments).forEach((commentsFilename) => {
         const extractedComments = new Set([

test/TerserPlugin.test.js

@@ -197,6 +197,52 @@ describe('TerserPlugin', () => {
     });
   });
 
+  it('should work in multi compiler mode with the one plugin and with the same file', async () => {
+    const plugins = [new TerserPlugin()];
+    const multiCompiler = getCompiler([
+      {
+        mode: 'production',
+        bail: true,
+        cache: getCompiler.isWebpack4() ? false : { type: 'memory' },
+        entry: `${__dirname}/fixtures/entry.js`,
+        output: {
+          path: `${__dirname}/dist-0`,
+          filename: '[name].js',
+          chunkFilename: '[id].[name].js',
+        },
+        optimization: {
+          minimize: false,
+        },
+        plugins,
+      },
+      {
+        mode: 'production',
+        bail: true,
+        cache: getCompiler.isWebpack4() ? false : { type: 'memory' },
+        entry: `${__dirname}/fixtures/entry.js`,
+        output: {
+          path: `${__dirname}/dist-1`,
+          filename: '[name].js',
+          chunkFilename: '[id].[name].js',
+        },
+        optimization: {
+          minimize: false,
+        },
+        plugins,
+      },
+    ]);
+
+    const multiStats = await compile(multiCompiler);
+
+    multiStats.stats.forEach((stats, index) => {
+      expect(
+        readsAssets(multiCompiler.compilers[index], stats)
+      ).toMatchSnapshot('assets');
+      expect(getErrors(stats)).toMatchSnapshot('errors');
+      expect(getWarnings(stats)).toMatchSnapshot('warnings');
+    });
+  });
+
   it('should work as a plugin', async () => {
     const compiler = getCompiler({
       plugins: [new TerserPlugin()],

test/__snapshots__/TerserPlugin.test.js.snap.webpack4

@@ -184,6 +184,26 @@ exports[`TerserPlugin should work as a plugin: errors 1`] = `Array []`;
 
 exports[`TerserPlugin should work as a plugin: warnings 1`] = `Array []`;
 
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: assets 1`] = `
+Object {
+  "main.js": "!function(e){var t={};function n(r){if(t[r])return t[r].exports;var o=t[r]={i:r,l:!1,exports:{}};return e[r].call(o.exports,o,o.exports,n),o.l=!0,o.exports}n.m=e,n.c=t,n.d=function(e,t,r){n.o(e,t)||Object.defineProperty(e,t,{enumerable:!0,get:r})},n.r=function(e){\\"undefined\\"!=typeof Symbol&&Symbol.toStringTag&&Object.defineProperty(e,Symbol.toStringTag,{value:\\"Module\\"}),Object.defineProperty(e,\\"__esModule\\",{value:!0})},n.t=function(e,t){if(1&t&&(e=n(e)),8&t)return e;if(4&t&&\\"object\\"==typeof e&&e&&e.__esModule)return e;var r=Object.create(null);if(n.r(r),Object.defineProperty(r,\\"default\\",{enumerable:!0,value:e}),2&t&&\\"string\\"!=typeof e)for(var o in e)n.d(r,o,function(t){return e[t]}.bind(null,o));return r},n.n=function(e){var t=e&&e.__esModule?function(){return e.default}:function(){return e};return n.d(t,\\"a\\",t),t},n.o=function(e,t){return Object.prototype.hasOwnProperty.call(e,t)},n.p=\\"\\",n(n.s=0)}([function(e,t){e.exports=function(){console.log(7)}}]);",
+}
+`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: assets 2`] = `
+Object {
+  "main.js": "!function(e){var t={};function n(r){if(t[r])return t[r].exports;var o=t[r]={i:r,l:!1,exports:{}};return e[r].call(o.exports,o,o.exports,n),o.l=!0,o.exports}n.m=e,n.c=t,n.d=function(e,t,r){n.o(e,t)||Object.defineProperty(e,t,{enumerable:!0,get:r})},n.r=function(e){\\"undefined\\"!=typeof Symbol&&Symbol.toStringTag&&Object.defineProperty(e,Symbol.toStringTag,{value:\\"Module\\"}),Object.defineProperty(e,\\"__esModule\\",{value:!0})},n.t=function(e,t){if(1&t&&(e=n(e)),8&t)return e;if(4&t&&\\"object\\"==typeof e&&e&&e.__esModule)return e;var r=Object.create(null);if(n.r(r),Object.defineProperty(r,\\"default\\",{enumerable:!0,value:e}),2&t&&\\"string\\"!=typeof e)for(var o in e)n.d(r,o,function(t){return e[t]}.bind(null,o));return r},n.n=function(e){var t=e&&e.__esModule?function(){return e.default}:function(){return e};return n.d(t,\\"a\\",t),t},n.o=function(e,t){return Object.prototype.hasOwnProperty.call(e,t)},n.p=\\"\\",n(n.s=0)}([function(e,t){e.exports=function(){console.log(7)}}]);",
+}
+`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: errors 1`] = `Array []`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: errors 2`] = `Array []`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: warnings 1`] = `Array []`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: warnings 2`] = `Array []`;
+
 exports[`TerserPlugin should work in multi compiler mode with the one plugin: assets 1`] = `
 Object {
   "main-1.js": "/******/ (function(modules) { // webpackBootstrap

test/__snapshots__/TerserPlugin.test.js.snap.webpack5

@@ -184,6 +184,26 @@ exports[`TerserPlugin should work as a plugin: errors 1`] = `Array []`;
 
 exports[`TerserPlugin should work as a plugin: warnings 1`] = `Array []`;
 
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: assets 1`] = `
+Object {
+  "main.js": "(()=>{var r={791:r=>{r.exports=function(){console.log(7)}}},o={};!function t(e){if(o[e])return o[e].exports;var n=o[e]={exports:{}};return r[e](n,n.exports,t),n.exports}(791)})();",
+}
+`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: assets 2`] = `
+Object {
+  "main.js": "(()=>{var r={791:r=>{r.exports=function(){console.log(7)}}},o={};!function t(e){if(o[e])return o[e].exports;var n=o[e]={exports:{}};return r[e](n,n.exports,t),n.exports}(791)})();",
+}
+`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: errors 1`] = `Array []`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: errors 2`] = `Array []`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: warnings 1`] = `Array []`;
+
+exports[`TerserPlugin should work in multi compiler mode with the one plugin and with the same file: warnings 2`] = `Array []`;
+
 exports[`TerserPlugin should work in multi compiler mode with the one plugin: assets 1`] = `
 Object {
   "main-1.js": "/******/ (() => { // webpackBootstrap