parcel-bundler / parcel-bundler/lightningcss
Avoid injecting `:is` in `:not` if all the arguments are known to be supported
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- Dominant language
- Rust
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Description
:not(a, block) {
color: blue;
}
is transformed to
:not(:-webkit-any(a, block)) {
color: #00f;
}
:not(:-moz-any(a, block)) {
color: #00f;
}
:not(:is(a, block)) {
color: #00f;
}
(playground).
But this isn't needed because a and block are both valid for the browser range.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by tracing the Rust selector transformation that handles :not() and compatibility fallbacks, using the CSS example in the issue as the reproduction. Done means the transformation does not inject :is or vendor-prefixed alternatives when all arguments are supported for the target browser range, while preserving required fallbacks in other cases.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100