Bring in terser-webpack-plugin (backport #6231 to master) (#6232)

* Bring in terser-webpack-plugin (backport #6231 to master)

* Use correct path for ignore

* Comment out schema

build/webpack.js

@@ -19,7 +19,7 @@ import ChunkNamesPlugin from './webpack/plugins/chunk-names-plugin'
 import { ReactLoadablePlugin } from './webpack/plugins/react-loadable-plugin'
 import {SERVER_DIRECTORY, NEXT_PROJECT_ROOT, NEXT_PROJECT_ROOT_NODE_MODULES, NEXT_PROJECT_ROOT_DIST, DEFAULT_PAGES_DIR, REACT_LOADABLE_MANIFEST, CLIENT_STATIC_FILES_RUNTIME_WEBPACK, CLIENT_STATIC_FILES_RUNTIME_MAIN} from '../lib/constants'
 import AutoDllPlugin from 'autodll-webpack-plugin'
-import TerserPlugin from 'terser-webpack-plugin'
+import TerserPlugin from './webpack/plugins/terser-webpack-plugin/src/cjs.js'
 
 // The externals config makes sure that
 // on the server side when modules are

build/webpack/plugins/terser-webpack-plugin/LICENSE

@@ -0,0 +1,20 @@
+Copyright JS Foundation and other contributors
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+'Software'), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

build/webpack/plugins/terser-webpack-plugin/src/TaskRunner.js

@@ -0,0 +1,106 @@
+import os from 'os';
+
+import cacache from 'cacache';
+import findCacheDir from 'find-cache-dir';
+import workerFarm from 'worker-farm';
+import serialize from 'serialize-javascript';
+
+import minify from './minify';
+
+const worker = require.resolve('./worker');
+
+export default class TaskRunner {
+  constructor(options = {}) {
+    const { cache, parallel } = options;
+    this.cacheDir =
+      cache === true ? findCacheDir({ name: 'terser-webpack-plugin' }) : cache;
+    // In some cases cpus() returns undefined
+    // https://github.com/nodejs/node/issues/19022
+    const cpus = os.cpus() || { length: 1 };
+    this.maxConcurrentWorkers =
+      parallel === true
+        ? cpus.length - 1
+        : Math.min(Number(parallel) || 0, cpus.length - 1);
+  }
+
+  run(tasks, callback) {
+    /* istanbul ignore if */
+    if (!tasks.length) {
+      callback(null, []);
+      return;
+    }
+
+    if (this.maxConcurrentWorkers > 1) {
+      const workerOptions =
+        process.platform === 'win32'
+          ? {
+              maxConcurrentWorkers: this.maxConcurrentWorkers,
+              maxConcurrentCallsPerWorker: 1,
+            }
+          : { maxConcurrentWorkers: this.maxConcurrentWorkers };
+      this.workers = workerFarm(workerOptions, worker);
+      this.boundWorkers = (options, cb) => {
+        try {
+          this.workers(serialize(options), cb);
+        } catch (error) {
+          // worker-farm can fail with ENOMEM or something else
+          cb(error);
+        }
+      };
+    } else {
+      this.boundWorkers = (options, cb) => {
+        try {
+          cb(null, minify(options));
+        } catch (error) {
+          cb(error);
+        }
+      };
+    }
+
+    let toRun = tasks.length;
+    const results = [];
+    const step = (index, data) => {
+      toRun -= 1;
+      results[index] = data;
+
+      if (!toRun) {
+        callback(null, results);
+      }
+    };
+
+    tasks.forEach((task, index) => {
+      const enqueue = () => {
+        this.boundWorkers(task, (error, data) => {
+          const result = error ? { error } : data;
+          const done = () => step(index, result);
+
+          if (this.cacheDir && !result.error) {
+            cacache
+              .put(
+                this.cacheDir,
+                serialize(task.cacheKeys),
+                JSON.stringify(data)
+              )
+              .then(done, done);
+          } else {
+            done();
+          }
+        });
+      };
+
+      if (this.cacheDir) {
+        cacache
+          .get(this.cacheDir, serialize(task.cacheKeys))
+          .then(({ data }) => step(index, JSON.parse(data)), enqueue);
+      } else {
+        enqueue();
+      }
+    });
+  }
+
+  exit() {
+    if (this.workers) {
+      workerFarm.end(this.workers);
+    }
+  }
+}

build/webpack/plugins/terser-webpack-plugin/src/cjs.js

@@ -0,0 +1,3 @@
+const plugin = require('./index');
+
+module.exports = plugin.default;