PostCSS Discard Overridden

PostCSS plugin to discard overridden @keyframes or @counter-style.

@keyframes or @counter-style will be overridden by those who share the same identifiers and appear later in stylesheets. So we can discard all of them except the last one. When defined inside a @media or @supports rule, @keyframes and @counter-style rules only override global rules in some of the client browsers so they need handled separately. This plugin has taken care of this and transforms the PostCss AST safely.

@-webkit-keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 0.8;
  }
}
@keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 0.8;
  }
}
@media (max-width: 500px) {
  @-webkit-keyframes fade-in {
    0% {
      opacity: 0;
    }
    100% {
      opacity: 1;
    }
  }
  @keyframes fade-in {
    0% {
      opacity: 0;
    }
    100% {
      opacity: 1;
    }
  }
  @-webkit-keyframes fade-in {
    0% {
      opacity: 0;
    }
    100% {
      opacity: 0.8;
    }
  }
  @keyframes fade-in {
    0% {
      opacity: 0;
    }
    100% {
      opacity: 0.8;
    }
  }
  @supports (display: flex) {
    @-webkit-keyframes fade-in {
      0% {
        opacity: 0;
      }
      100% {
        opacity: 1;
      }
    }
    @keyframes fade-in {
      0% {
        opacity: 0;
      }
      100% {
        opacity: 1;
      }
    }
  }
}
@-webkit-keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}
@keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}

@media (max-width: 500px) {
  @-webkit-keyframes fade-in {
    0% {
      opacity: 0;
    }
    100% {
      opacity: 0.8;
    }
  }
  @keyframes fade-in {
    0% {
      opacity: 0;
    }
    100% {
      opacity: 0.8;
    }
  }
  @supports (display: flex) {
    @-webkit-keyframes fade-in {
      0% {
        opacity: 0;
      }
      100% {
        opacity: 1;
      }
    }
    @keyframes fade-in {
      0% {
        opacity: 0;
      }
      100% {
        opacity: 1;
      }
    }
  }
}
@-webkit-keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}
@keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}

Usage

postcss([ require('postcss-discard-overridden') ])

See PostCSS docs for examples for your environment.