Incorrect compilation when extending %placeholder which has parent selectors inside

[ah-yu]

Hi sass team，

I am currently facing a problem in the process of migrating node-sass to sass. See the minimal reproducible example below.

// test.scss
%foo {
  &:hover {
    background-color: blue;
  }

  @media (min-width: 500px) {
    &,
    &:hover {
      background-color: red;
    }
  }
}

.bar {
  @extend %foo;
}

the compilation of sass

.bar:hover {
  background-color: blue;
}
@media (min-width: 500px) {
  /* .bar:hover is missing */
  .bar { 
    background-color: red;
  }
}

expected compilation(the output of node-sass)

.bar:hover {
  background-color: blue; 
}

@media (min-width: 500px) {
  .bar, .bar:hover {
    background-color: red; 
  } 
}

[connorskees]

This is reproducible without @media or placeholder selectors:

a, a:hover {
    background-color: red;
}

// for comparison only. not necessary for reproduction
a:hover {
    background-color: blue;
}

b {
    @extend a;
}

will output

// missing b:hover
a, b,
a:hover {
  background-color: red;
}

// contains b:hover
a:hover, b:hover {
  background-color: blue;
}

Perhaps this is because b is being considered a super selector of b:hover and so b:hover is considered superfluous and is omitted?

ruby sass does emit the b:hover, which I would argue is the correct behavior.

[jathak]

This is working as intended, as any element matching b:hover would inherently have to match b, and the second law of extend only requires the new selector's specificity to be greater or equal to the extender (b in this case), not the extendee.