cssplus

Expands nested CSS rules efficiently by fuzzy parsing and not validating the specific syntax of selectors and property values.

Install

$ yarn add @multiprocess/cssplus

Use

import fs from 'fs';
import { transform } from '@multiprocess/cssplus';

const myCSSPlusFile = fs.readFileSync('myfile.css').toString();
const css = transform(myCSSPlusFile);

Command-line example

This repo includes a number of example files that should be correctly transformed.

$ cat examples/all-basic-features.css
input .input, button .button {
  color: white;
  border: 1px solid blue;

  a[value="{foobar,"] {
    font-size: 0;
  }
}

.container {
  .row {
    .col {
      display: flex;
    }
  }
}


/* Testing out some things */

a {
  background: url('mygreaturl;).,}{');
}

@keyframes pulse {
  0% {
    background: white;
  }
  50% {
    background: red;
  }
}

Run:

$ yarn && yarn build
$ node ./scripts/cssplus.js examples/all-basic-features.css
input .input,
button .button {
  color: white;
  border: 1px solid blue;
}

input .input a[value="{foobar,"],
button .button a[value="{foobar,"] {
  font-size: 0;
}

.container .row .col {
  display: flex;
}

a {
  background: url('mygreaturl;).,}{');
}

@keyframes pulse {
  0% {
    background: white;
  }
  50% {
    background: red;
  }
}

Benchmarks

This library is a good deal faster than the JavaScript sass parser and closer to the native C++ libsass parser:

$ cd ./benchmarks && yarn

$ time node ./js-scss-runner.js ./tens-of-thousands-of-rules.scss > js-scss-out
node ./js-scss-runner.js ./tens-of-thousands-of-rules.scss > js-scss-out  1.23s user 0.05s system 156% cpu 0.820 total

$ time node ./native-scss-runner.js ./tens-of-thousands-of-rules.scss > native-scss-out
node ./native-scss-runner.js ./tens-of-thousands-of-rules.scss >   0.31s user 0.04s system 102% cpu 0.338 total

$ time node ./cssplus-runner.js ./tens-of-thousands-of-rules.scss > cssplus-out
node ./cssplus-runner.js ./tens-of-thousands-of-rules.scss > cssplus-out  0.37s user 0.02s system 157% cpu 0.246 total

Again, this is only possible because this library does no validation of selectors or property values.

Nested rule support

For some reason, this library handles massively nested rules better than the JavaScript sass library and C++ sass library.

$ cd ./benchmarks && yarn

$ time node ./cssplus-runner.js ./too-nested.scss > cssplus-out 
node ./cssplus-runner.js ./too-nested.scss > cssplus-out  2.90s user 0.48s system 180% cpu 1.870 total

$ time node ./js-scss-runner.js ./too-nested.scss > js-scss-out                        
undefined:3
throw error;
^

Error: Stack Overflow
    at Object._newRenderError (/home/phil/multiprocess/cssplus/benchmarks/node_modules/sass/sass.dart.js:16144:19)
    at StaticClosure.renderSync (/home/phil/multiprocess/cssplus/benchmarks/node_modules/sass/sass.dart.js:15947:23)
    at Object.Primitives_applyFunction (/home/phil/multiprocess/cssplus/benchmarks/node_modules/sass/sass.dart.js:6140:30)
    at Object.Function_apply (/home/phil/multiprocess/cssplus/benchmarks/node_modules/sass/sass.dart.js:13486:16)
    at _callDartFunctionFast (/home/phil/multiprocess/cssplus/benchmarks/node_modules/sass/sass.dart.js:15192:16)
    at Object.renderSync (/home/phil/multiprocess/cssplus/benchmarks/node_modules/sass/sass.dart.js:15170:18)
    at Object.<anonymous> (/home/phil/multiprocess/cssplus/benchmarks/js-scss-runner.js:2:18)
    at Module._compile (internal/modules/cjs/loader.js:1085:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)
    at Module.load (internal/modules/cjs/loader.js:950:32) {
  formatted: 'Error: Stack Overflow',
  status: 3
}
node ./js-scss-runner.js ./too-nested.scss > js-scss-out  0.29s user 0.04s system 115% cpu 0.283 total

$ time node ./native-scss-runner.js ./too-nested.scss > native-scss-out
/home/phil/multiprocess/cssplus/benchmarks/node_modules/node-sass/lib/index.js:440
  throw Object.assign(new Error(), JSON.parse(result.error));
  ^

Error: Code too deeply neested
    at Object.module.exports.renderSync (/home/phil/multiprocess/cssplus/benchmarks/node_modules/node-sass/lib/index.js:440:23)
    at Object.<anonymous> (/home/phil/multiprocess/cssplus/benchmarks/native-scss-runner.js:2:18)
    at Module._compile (internal/modules/cjs/loader.js:1085:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)
    at Module.load (internal/modules/cjs/loader.js:950:32)
    at Function.Module._load (internal/modules/cjs/loader.js:790:12)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:76:12)
    at internal/main/run_main_module.js:17:47 {
  status: 1,
  file: '/home/phil/multiprocess/cssplus/benchmarks/too-nested.scss',
  line: 511,
  column: 256,
  formatted: 'Error: Code too deeply neested\n' +
    '        on line 511 of too-nested.scss\n' +
    '>> \t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tdiv {\n' +
    '\n' +
    '   ------------------------------------------^\n'
}
node ./native-scss-runner.js ./too-nested.scss > native-scss-out  0.13s user 0.01s system 109% cpu 0.127 total