fix(issue:4264) strip line comment from expression

[puckowski]

What:

Fix for issue #4264. Strip line comments from expressions to avoid invalid CSS output.

Why:

Less.js currently takes CSS like:

@items:
// Fruit
    apple,
    banana,
    cherry,

// Vegetables
    carrot,
    potato,
;

each(@items, {
  div#@{value} {
    color: blue;
  }
})

and outputs:

div#apple {
  color: blue;
}
div#banana {
  color: blue;
}
div#cherry {
  color: blue;
}
div#// Vegetables carrot {
  color: blue;
}
div#potato {
  color: blue;
}

With fix the output is:

div#apple {
  color: blue;
}
div#banana {
  color: blue;
}
div#cherry {
  color: blue;
}
div#carrot {
  color: blue;
}
div#potato {
  color: blue;
}

Checklist:

• Documentation
• Added/updated unit tests
• Code complete

Tests passing locally. Updated tests for variables.

[puckowski]

I submitted a few PRs. I expect rebase(s) will be needed in order to merge all of them, so let me know when a rebase is needed.

[puckowski]

Rebased after merge conflict. Changes approved by one reviewer. Some CI looks flaky. Squashing and merging to avoid future merge conflicts.