Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.12)
// Compass (v1.0.3)
// ----

$__aggregate-map__: () !global;

@mixin aggregate($property, $value, $separator: comma) {
  @if map-get($__aggregate-map__, &) == null {
    $__aggregate-map__: map-merge($__aggregate-map__, (&: ())) !global;
  }
  
  $agg-selector-value: map-get($__aggregate-map__, &);
  $agg-property-value: map-get($agg-selector-value, $property);
  
  @if $agg-property-value == null {
    $agg-property-value: ($value,);
  } @else {
    $agg-property-value: append($agg-property-value, $value, $separator);   
  }
  
  $agg-selector-value: map-merge($agg-selector-value, ($property: $agg-property-value));
  
  $__aggregate-map__: map-merge($__aggregate-map__, (&: $agg-selector-value)) !global;
}

@mixin \+($property, $value) {
  @include aggregate($property, $value, comma);
}

@mixin \+_($property, $value) {
  @include aggregate($property, $value, space);
}

@function \=($property) {
  $selector-value: map-get($__aggregate-map__, &);
  $property-value: null;
  
  @if $selector-value {
    $property-value: map-get($selector-value, $property);
    
    @if length($property-value) == 1 {
      $property-value: nth($property-value, 1);
    }
  }
  
  $selector-value: map-remove($selector-value, $property);
  
  $__aggregate-map__: map-merge($__aggregate-map__, (&: $selector-value)) !global;
  
  @return inspect($property-value);
}

// Usage
// =====
@mixin my-mixin() {
  @include \+(box-shadow, 0 10px 20px green);
  @include \+(transition-property, width);
}

.my-class {
  @include \+(box-shadow, inset 0 0 10px #555);
  @include \+(box-shadow, 0 0 20px black);
  
  @include \+(transition-property, height);
  @include \+(transition-property, opacity);
  
  @include my-mixin();
  
  .child-animated-class {
    @include \+(animation-name, foo);
    @include \+(animation-name, bar);
    
    animation-name: \=(animation-name);
  }
  
  box-shadow: \=(box-shadow);
  transition-property: \=(transition-property);
}

.my-other-class {
  @include \+_(transform, scale(2));
  @include \+_(transform, rotate(15deg));
  
  @include \+_(padding, 10px);
  
  transform: \=(transform);
  padding: \=(padding);
}

SassMeister-output.css

.my-class {
  box-shadow: inset 0 0 10px #555, 0 0 20px black, 0 10px 20px green;
  transition-property: height, opacity, width;
}
.my-class .child-animated-class {
  animation-name: foo, bar;
}

.my-other-class {
  transform: scale(2) rotate(15deg);
  padding: 10px;
}