feat: add one-letter-css plugin

README.md

@@ -1348,6 +1348,47 @@ import styles from 'Component.module.scss';
 ctx.fillStyle = `${svars.colorBackgroundCanvas}`;
 ```
 
+### Plugin: One Letter CSS (with hash length check)
+
+For efficient gzip/br compression, plugin combine css hash via one symbol name,
+as a classname position at file, with filepath `hash:base64:8`, to have strong sequences
+
+**webpack.config.js**
+
+```js
+const { HashLenSuggest, OneLetterCss } = require('css-loader/plugins');
+const MyOneLetterCss = new OneLetterCss();
+
+const cssHashLen = 8;
+
+module.exports = {
+  module: {
+    rules: [
+      {
+        test: /\.css$/i,
+        loader: 'css-loader',
+        options: {
+          modules: {
+            mode: 'local',
+            localIdentName: `[hash:base64:${cssHashLen}]`,
+            // for develop
+            // localIdentName: `[local]__[hash:base64:${cssHashLen}]`,
+            getLocalIdent: MyOneLetterCss.getLocalIdent,
+          },
+        },
+      },
+    ],
+  },
+  plugins: [
+    ...plugins,
+    new HashLenSuggest({
+      instance: MyOneLetterCss,
+      selectedHashLen: cssHashLen,
+    }),
+  ],
+};
+```
+
 ## Contributing
 
 Please take a moment to read our contributing guidelines if you haven't yet done so.

src/plugins/hash-len-suggest.js

@@ -0,0 +1,59 @@
+const PLUGIN_NAME = 'Hash length suggest';
+
+export default class HashLenSuggest {
+  constructor({ instance, selectedHashLen }) {
+    this.instance = instance;
+    this.selectedHashLen = selectedHashLen;
+    this.logger = null;
+  }
+
+  apply(compiler) {
+    compiler.plugin('done', this.run);
+
+    this.logger = compiler.getInfrastructureLogger(PLUGIN_NAME);
+  }
+
+  run() {
+    let data = this.instance.getStat();
+    const matchLen = {};
+    const base = {};
+
+    Object.values(data).forEach(({ name }) => {
+      for (let len = 1; len <= name.length; len += 1) {
+        base[len] = base[len] || {};
+        const hash = name.substr(0, len);
+
+        if (base[len][hash]) {
+          matchLen[len] = matchLen[len] || 0;
+          matchLen[len] += 1;
+        } else {
+          base[len][hash] = 1;
+        }
+      }
+    });
+
+    data = null;
+
+    const { logger, selectedHashLen } = this;
+
+    logger.log('Suggest Minify Plugin');
+    logger.log('Matched length (len: number):', matchLen);
+
+    if (matchLen[selectedHashLen]) {
+      logger.log(
+        `🚫 You can't use selected hash length (${selectedHashLen}). Increase the hash length.`
+      );
+      process.exit(1);
+    } else {
+      logger.log(`Selected hash length (${selectedHashLen}) is OK.`);
+
+      if (!matchLen[selectedHashLen - 1]) {
+        logger.log(
+          `🎉 You can decrease the hash length (${selectedHashLen} -> ${
+            selectedHashLen - 1
+          }).`
+        );
+      }
+    }
+  }
+}

src/plugins/index.js

@@ -1,5 +1,7 @@
 import importParser from './postcss-import-parser';
 import icssParser from './postcss-icss-parser';
 import urlParser from './postcss-url-parser';
+import HashLenSuggest from './hash-len-suggest';
+import OneLetterCss from './one-letter-css';
 
-export { importParser, icssParser, urlParser };
+export { HashLenSuggest, OneLetterCss, importParser, icssParser, urlParser };

src/plugins/one-letter-css.js

@@ -0,0 +1,209 @@
+const { interpolateName } = require('loader-utils');
+
+/**
+ * Change css-classes to 64-bit prefix (by class position at file) + hash postfix (by file path)
+ */
+
+// Parse encoding string, or get default values
+const getRule = (externalRule) => {
+  let iRule = {
+    type: 'hash',
+    rule: 'base64',
+    hashLen: 8,
+    val: '',
+  };
+
+  iRule.val = `[${iRule.type}:${iRule.rule}:${iRule.hashLen}]`;
+
+  const matchHashRule =
+    externalRule
+      .replace(/_/g, '')
+      .match(/^(?:\[local])*\[([a-z\d]+):([a-z\d]+):(\d+)]$/) || [];
+
+  if (matchHashRule.length >= 4) {
+    const [, type, rule, hashLen] = matchHashRule;
+
+    iRule = {
+      type,
+      rule,
+      hashLen,
+      val: `[${type}:${rule}:${hashLen}]`,
+    };
+  }
+
+  return iRule;
+};
+
+export default class OneLetterCssClasses {
+  constructor() {
+    // Save separators points from ascii-table
+    this.a = 'a'.charCodeAt(0);
+    this.A = 'A'.charCodeAt(0);
+    this.zero = '0'.charCodeAt(0);
+    this.files = {};
+    // [a-zA-Z\d_-]
+    this.encoderSize = 64;
+    this.symbolsArea = {
+      // a-z
+      az: 26,
+      // A-Z
+      AZ: 52,
+      // _
+      under: 53,
+      // 0-9 | \d
+      digit: 63,
+      // -
+      // dash: 64
+    };
+    // prevent loop hell
+    this.maxLoop = 5;
+    this.rootPathLen = process.cwd().length;
+  }
+
+  getSingleSymbol(n) {
+    const {
+      a,
+      A,
+      zero,
+      encoderSize,
+      symbolsArea: { az, AZ, under, digit },
+    } = this;
+
+    if (!n) {
+      // console.error(`!n, n=${n}`);
+      return '';
+    }
+
+    if (n > encoderSize) {
+      // console.error(`n > ${encoderSize}, n=${n}`);
+      return '';
+    }
+
+    // work with 1 <= n <= 64
+    if (n <= az) {
+      return String.fromCharCode(n - 1 + a);
+    }
+
+    if (n <= AZ) {
+      return String.fromCharCode(n - 1 - az + A);
+    }
+
+    if (n <= under) {
+      return '_';
+    }
+
+    if (n <= digit) {
+      return String.fromCharCode(n - 1 - under + zero);
+    }
+
+    return '-';
+  }
+
+  /** Encode classname by position at file, 0 - a, 1 - b, etc */
+  getNamePrefix(num) {
+    const { maxLoop, encoderSize } = this;
+
+    if (!num) {
+      return '';
+    }
+
+    let loopCount = 0;
+    let n = num;
+    let res = '';
+
+    // Divide at loop for 64
+    // For example, from 1 to 64 - 1 step, from 65 to 4096 (64*64) - 2 steps, etc
+    while (n && loopCount < maxLoop) {
+      // Remainder of division, for 1-64 encode
+      let tail = n % encoderSize;
+      const origTail = tail;
+
+      // Check limits, n === encoderSize. 64 % 64 = 0, but encoding for 64
+      if (tail === 0) {
+        tail = encoderSize;
+      }
+
+      // Concat encoding result
+      res = this.getSingleSymbol(tail) + res;
+
+      // Check for new loop
+      if (Math.floor((n - 1) / encoderSize)) {
+        // Find the number of bits for next encoding cycle
+        n = (n - origTail) / encoderSize;
+
+        // At limit value (64), go to a new circle,
+        // -1 to avoid (we have already encoded this)
+        //
+        if (origTail === 0) {
+          n -= 1;
+        }
+      } else {
+        n = 0;
+      }
+
+      loopCount += 1;
+    }
+
+    return res;
+  }
+
+  /**
+   * Make hash
+   */
+  getLocalIdentWithFileHash(context, localIdentName, localName) {
+    const { resourcePath } = context;
+    const { files, rootPathLen } = this;
+
+    // To fix difference between stands, work with file path from project root
+    const resPath = resourcePath.substr(rootPathLen);
+
+    // Filename at list, take his name
+    let fileShort = files[resPath];
+
+    // Filename not at list, generate new name, save
+    if (!fileShort) {
+      // parse encoding rule
+      const localIdentRule = getRule(localIdentName);
+
+      const fileShortName = interpolateName(context, localIdentRule.val, {
+        content: resPath,
+      });
+
+      fileShort = { name: fileShortName, lastUsed: 0, ruleNames: {} };
+      files[resPath] = fileShort;
+    }
+
+    // Take rulename, if exists at current file
+    let newRuleName = fileShort.ruleNames[localName];
+
+    // If rulename not exist - generate new, and save
+    if (!newRuleName) {
+      // Increase rules count
+      fileShort.lastUsed += 1;
+
+      // Generate new rulename
+      newRuleName = this.getNamePrefix(fileShort.lastUsed) + fileShort.name;
+
+      // Save rulename
+      fileShort.ruleNames[localName] = newRuleName;
+    }
+
+    // Check encoding settings for local development (save original rulenames)
+    const hasLocal = /\[local]/.test(localIdentName);
+
+    // If develop mode - add prefix
+    const res = hasLocal ? `${localName}__${newRuleName}` : newRuleName;
+
+    // Add prefix '_' for classes with '-' or digit '\d'
+    // or '_' (for fix collision)
+    return /^[\d_-]/.test(res) ? `_${res}` : res;
+  }
+
+  getStat() {
+    const stat = { ...this.files };
+
+    this.files = {};
+
+    return stat;
+  }
+}