A Sass @mixin to generate silent extension class patterns.

about.silent-sass-extension.md

Silent Sass Extension

Running this Gist through Sass should generate the following output:

.underridden { // $XELIDE: true !default
  color: magenta;
}

.underridden {
  color: red;
}
.overridden {
  color: blue;
}

.overridden, .override { // $XELIDE: false
  color: magenta;
}

main.scss

// $XELIDE: false;

@import "pattern.core";
@import "underride.partial";

.underridden {
  @extend %underr;
  color: red;
}

.overridden {
  @extend %overr;
  color: blue;
}

@import "override.partial"

override.partial.scss

@include x(overr){
  color: cyan;
}

pattern.core.scss

$XELIDE: false !default;

@mixin x($patternName, $elide: true){
  $elide: if($elide, $XELIDE, false);
  $class: '%#{$patternName}';

  @if not $elide {
    $class: '#{$class}, .#{$patternName}';
  }

  #{$class} { @content }
}

underride.partial.scss

@include x(underr){
  color: magenta;
}