Incorrect evaluation of arithmetic inside interpolation

[xzyfer]

The behaviour of this changed LibSass 3.4. Interestingly in this case Ruby Sass' output is also incorrect. A bug has been filed with Ruby Sass also sass/sass#2160.

foo {
  a: #{5% / 2};
  b: #{+5% / 2};
  c: #{-5% / 2};
}

Expected output

foo {
  a: 5%/2;
  b: 5%/2;
  c: -5%/2;
}

LibSass 3.4 RC

foo {
  a: 2.5%;
  b: 2.5%;
  c: -2.5%;
}

Ruby Sass 3.4.21

foo {
  a: 5%/2;
  b: 5%/2;
  c: -2.5%;
}

Spec sass/sass-spec#940

[xzyfer]

The behaviour exhibited by LibSass here is different from Ruby Sass, but it is no more or less inconsistent. I don't believe this should block 3.4 unless it arises as an issue during RC.

We'll address this for good when sass/sass#2160 is resolved.

[xzyfer]

Rescoping this to post 3.4.

[mgreter]

@nex3 @chriseppstein is there a reason why ruby sass 3.5.5 still has this "unexpected" behavior? I believe this stems from static value parsing in ruby sass? Any plans if this will change in future versions? And if so, in what direction, leave it as is, or evaluate it as libsass currently does?

[nex3]

It just hasn't been a high priority to fix—as far as I know, it hasn't come up in any real code. -5%/2 is the correct output, so that's what libsass should target.