feat: add cache and parallel

package.json

@@ -41,9 +41,13 @@
     "webpack": "^4.0.0 || ^5.0.0"
   },
   "dependencies": {
+    "cacache": "^15.0.5",
     "cssnano": "^4.1.10",
+    "find-cache-dir": "^3.3.1",
+    "jest-worker": "^26.1.0",
     "p-limit": "^3.0.2",
     "schema-utils": "^2.7.0",
+    "serialize-javascript": "^4.0.0",
     "source-map": "^0.6.1",
     "webpack-sources": "^1.4.3"
   },

src/Webpack4Cache.js

@@ -0,0 +1,35 @@
+import os from 'os';
+
+import cacache from 'cacache';
+import findCacheDir from 'find-cache-dir';
+import serialize from 'serialize-javascript';
+
+export default class Webpack4Cache {
+  constructor(compilation, options) {
+    this.cacheDir =
+      options.cache === true
+        ? Webpack4Cache.getCacheDirectory()
+        : options.cache;
+  }
+
+  static getCacheDirectory() {
+    return findCacheDir({ name: 'cssnano-webpack-plugin' }) || os.tmpdir();
+  }
+
+  isEnabled() {
+    return Boolean(this.cacheDir);
+  }
+
+  get(task) {
+    // eslint-disable-next-line no-param-reassign
+    task.cacheIdent = task.cacheIdent || serialize(task.cacheKeys);
+
+    return cacache
+      .get(this.cacheDir, task.cacheIdent)
+      .then(({ data }) => JSON.parse(data));
+  }
+
+  store(task, data) {
+    return cacache.put(this.cacheDir, task.cacheIdent, JSON.stringify(data));
+  }
+}

src/Webpack5Cache.js

@@ -0,0 +1,75 @@
+// eslint-disable-next-line import/extensions,import/no-unresolved
+import getLazyHashedEtag from 'webpack/lib/cache/getLazyHashedEtag';
+import serialize from 'serialize-javascript';
+
+import { util } from 'webpack';
+
+export default class Cache {
+  // eslint-disable-next-line no-unused-vars
+  constructor(compilation, ignored) {
+    this.compilation = compilation;
+  }
+
+  isEnabled() {
+    return Boolean(this.compilation.cache);
+  }
+
+  createCacheIdent(task) {
+    const {
+      outputOptions: { hashSalt, hashDigest, hashDigestLength, hashFunction },
+    } = this.compilation;
+
+    const hash = util.createHash(hashFunction);
+
+    if (hashSalt) {
+      hash.update(hashSalt);
+    }
+
+    hash.update(serialize(task.cacheKeys));
+
+    const digest = hash.digest(hashDigest);
+    const cacheKeys = digest.substr(0, hashDigestLength);
+
+    return `${this.compilation.compilerPath}/CssnanoWebpackPlugin/${cacheKeys}/${task.file}`;
+  }
+
+  get(task) {
+    // eslint-disable-next-line no-param-reassign
+    task.cacheIdent = task.cacheIdent || this.createCacheIdent(task);
+    // eslint-disable-next-line no-param-reassign
+    task.cacheETag = task.cacheETag || getLazyHashedEtag(task.assetSource);
+
+    return new Promise((resolve, reject) => {
+      this.compilation.cache.get(
+        task.cacheIdent,
+        task.cacheETag,
+        (err, result) => {
+          if (err) {
+            reject(err);
+          } else if (result) {
+            resolve(result);
+          } else {
+            reject();
+          }
+        }
+      );
+    });
+  }
+
+  store(task, data) {
+    return new Promise((resolve, reject) => {
+      this.compilation.cache.store(
+        task.cacheIdent,
+        task.cacheETag,
+        data,
+        (err) => {
+          if (err) {
+            reject(err);
+          } else {
+            resolve(data);
+          }
+        }
+      );
+    });
+  }
+}