YACP

Yet Another CSS Preprocessor.

Installation

$ npm install -g yacp

when use in HTML:

$ bower install client-yacp

Example

/* Import your other CSS files */
@import url("foo.css") 
 
/* Define variables in W3C syntax */
:root { 
  --font-lg: 18px;
}
 
/* Placeholder selector for `extend` */
%att {
  color: red;
  font-weight: normal;
}
 
.attBox {
  extend: %att; /* Extend `%att` */
  box-shadow: 5px 5px;
  font-size: var(--font-lg); /* Use variable `--font-lg` */
  padding: 5px 10px;
}

Compiled with the following command:

$ yacp input.css output.css

Yields:

/* Expand foo.css */
.foo {
 
}
 
/* Inherited in `.attBox` */
.attBox {
  color: red;
  font-weight: normal;
}
 
.attBox {
  -webkit-box-shadow: 5px 5px; /* Automatically added vendor prefix */
  box-shadow: 5px 5px;
  font-size: 18px; /* Expand the variable */
  padding: 5px 10px;
}

Features

• Automatic vendor-prefixed property
• Rulesets binding syntax
• Inherit other rules more safely
• W3C-style CSS variables syntax
• Support calc(), a feature to do simple calculations
• Read and inline css via @import

Bind ruleset syntax

YACP provide Bind ruleset syntax.

Selectors rounded by () cannot cascade.

Using this feature, you can define encapsulated ruleset.

(.btn) {
  background-color; #4dac26;
  border: solid 1px #2c9700;
  color: #fff;
  font-size: 16px;
  padding: 12px 8px;
}
 
/* Error */
.btn {
  padding: 15px 10px;
}
/* Error */
(.btn) {
  padding: 15px 10px;
}

Inherit other rulesets safely

One of fault of existin CSS Preprocessor is compiling any code which don't have syntax error.

This is 'dangerous' inheritance code (Sass):

.btn {
  border-radius: 5px;
  color: #fff;
  padding: 6px 12px;
}
 
.btn-success {
  @extend .btn;
  background-color: #4dac26;
}
 
...
 
.btn {
  padding: 8px 16px;
}

Yields:

.btn, .btn-success {
  border-radius: 5px;
  color: #fff;
  padding: 6px 12px;
}
 
.btn-success {
  background-color: #4dac26;
}
 
...
 
.btn, .btn-success {
  padding: 8px 16px;
}

When overwrite .btn, .btn-success is overwrote too, and it may cause unexpected result.

But, YACP's inheritance is safe. You can use with extend(s) or inherit(s) property.

1. Must use the placeholder selector (%). The Ruleset defined with placeholder selector don't output as CSS code.

2. YACP's placeholder selector cannot cascade.

3. If inherited selectors have same properties, run error.

Ex (1, 2):

%btn {
  border-radius: 5px;
  color: #fff;
  padding: 6px 12px;
}
 
.btn-success {
  extend: %btn;
  background-color: var(--color-green);
}
 
/* Error */
%btn {
  padding: 8px 16px;
}

Ex (3):

%foo {
  font-size: 16px;
  padding: 5px 10px;
}
 
%bar {
  color: #fff;
  font-size: 14px;
}
 
.baz {
  /* Error */
  extend: %foo;
  extend: %bar;
}

Using this feature, you can define private (cannot overwrite and refer from only YACP code) ruleset.

Compile Options

$ yacp --help

Usage: yacp [options]

Options:

  -c, --compress    use output compression
  -s, --strict      use strict mode compile
  -w, --whitespace  use whitespace syntax like Stylus
  -V, --versions    output the version number
  -h, --help        output usage information

strict mode

YACP's strict mode allow only class and pseudo-elements selector.

Following selectors cannot compile.

Ex:

#id {}
 
div {}
 
.class .nested {}
 
p.class {}

and prohibit !important.

.class {
  /* Error */
  padding: 0 !important;
}

Using this option, you can keep specificity constant, so its code will be more maintenable.

whitespace mode

Using with css-whitespace.

Option projects

• grunt-yacp

License

The MIT License (MIT)

Copyright (c) 2014 Masaaki Morishita