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64 lines
2.2 KiB
Plaintext
64 lines
2.2 KiB
Plaintext
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---
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title: "Breaking Change: Invalid Combinators"
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introduction: >
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Sass has historically been very permissive about the use of leading, trailing,
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and repeated combinators in selectors. These combinators are being deprecated
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except where they're useful for nesting.
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---
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Sass has historically supported three invalid uses of combinators:
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* Leading combinators, as in `+ .error {color: red}`.
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* Trailing combinators, as in `.error + {color: red}`.
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* Repeated combiantors, as in `div > > .error {color: red}`.
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None of these are valid CSS, and all of them will cause browsers to ignore the
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style rule in question. Supporting them added a substantial amount of complexity
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to Sass's implementation, and made it particularly difficult to fix various bugs
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related to the `@extend` rule. As such, we [made the decision] to remove support
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for these uses.
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[made the decision]: https://github.com/sass/sass/issues/3340
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**There is one major exception**: leading and trailing combinators may still be
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used for nesting purposes. For example, the following is still very much
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supported:
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<% example do %>
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.sidebar > {
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.error {
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color: red;
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}
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}
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===
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.sidebar >
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.error
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color: red
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<% end %>
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Sass will only produce an error if a selector still has a leading or trailing
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combinator _after nesting is resolved_. Repeated combinators, on the other hand,
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will always be errors.
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To make sure existing stylesheets who (likely accidentally) contain invalid
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combinators, we'll support a transition period until the next major release of
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Dart Sass.
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## Transition Period
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<% impl_status dart: '1.54.0', libsass: false, ruby: false %>
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First, we'll emit deprecation warnings all double combinators, as well as
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leading or trailing combinators that end up in selectors after nesting is
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resolved.
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<%= partial '../snippets/silence-deprecations' %>
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In addition, we'll immediately start omitting selectors that we know to be
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invalid CSS from the compiled CSS, with one exception: we _won't_ omit selectors
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that begin with a leading combinator, since they may be used from a nested
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`@import` rule or `meta.load-css()` mixin. However, we don't encourage this
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pattern and will drop support for it in Dart Sass 2.0.0.
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