libsass chokes on Compass stylesheet's "prefix-usage(" call

[ochafik]

Not sure if that's Compass not abiding by Scss syntax, or some bug in libsass.

Repro: given foo.scss:

@import 'compass/css3/flexbox';
.foo {
  @include display-flex(inline-flex);
}

The following command:

gem install sass compass
sassc -I `gem environment gemdir`/gems/compass-core-1.0.3/stylesheets foo.scss

Yields this error:

Error: may only compare numbers
        on line 323 of ../../.rvm/gems/jruby-1.7.19/gems/compass-core-1.0.3/stylesheets/compass/_support.scss
>>   $usage: prefix-usage($prefix, $capability, $capability-options);
   ----------^

See corresponding line in Compass' github source.

(this is blocking a large migration from Ruby Sass to SassC, as migrating to more libsass-friendly mixin libraries like Bourbon is a larger investment)

Output of sassc --version:

sassc: 3.3.0
libsass: 3.3.3
sass2scss: 1.0.5

[ochafik]

Mmh, ok, that error message was a red herring, the root cause is the line below, which looks like #1451. Probably because prefix-usage is a Compass builtin :-(

  $usage: prefix-usage($prefix, $capability, $capability-options);
  @if $usage > $threshold {

[ochafik]

The right way to go might just be to use autoprefixer and hard code some constant prefix-usage to trick the Compass stylesheets into not using prefixes at all.

Closing this issue.

[laomatt]

just to add what finally worked for me, i tried to look for the source code, but this function isn't shared on compasses website. Its an old code base that hasn't been updated in a long time, so I finally just had to make the function myself:

@function prefix-usage($prefix, $capability, $capability-options: $default-capability-options) {
  $result: ();
  @each $prefix in browser-prefixes($supported-browsers) {
    $result: append($result, 3);
  }
  @return length($result);
}