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117 lines
4.9 KiB
Markdown
117 lines
4.9 KiB
Markdown
---
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title: "Feature Watch: CSS Imports and CSS Compatibility"
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author: Natalie Weizenbaum
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date: 2018-08-13 14:17 PST
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---
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Dart Sass 1.11 has just been released, and with it a handful of new features.
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This is an exciting moment, because it marks the first major new feature that's
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been added to the language since Dart Sass was launched. It's also the first
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release with features that have gone through the new process, from
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[proposal](https://github.com/sass/language/blob/main/accepted/css-imports.md)
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to [tests](https://github.com/sass/sass-spec/pull/1277) to
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[implementation](https://github.com/sass/dart-sass/pull/436).
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### CSS Imports
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The biggest feature in Dart Sass 1.11 is support for importing plain CSS files.
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This is a long-awaited feature, and while we'd initially planned on waiting on
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it until we launched the upcoming module system, we ended up deciding to
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[implement it earlier](/blog/request-for-commentsimporting-css-files).
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You can now import a CSS file, say `styles.css`, just by writing `@import
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"styles"`. That file will be parsed as plain CSS, which means that any Sass
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features like variables or mixins or interpolation will be disallowed. The CSS
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it defines will become part of your stylesheet, and can be `@extend`ed just like
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any other styles.
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There are a couple caveats: because SCSS is a superset of plain CSS, it will
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still compile `@import "styles.css"` (with an explicit extension) to a CSS
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`@import` rule. If you want to import a CSS file into your Sass compilation, you
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must omit the extension.
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Also, this feature isn't fully [implemented in
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LibSass](https://github.com/sass/libsass/issues/2699) yet. It still has its old
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behavior, where it imports CSS files but parses them as SCSS, with all the extra
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Sass features allowed. This behavior will be deprecated soon, and eventually it
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will produce errors for anything other than plain CSS, just like Dart Sass does
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today.
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### CSS `min()` and `max()`
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Dart Sass 1.11 also adds support for CSS's `min()` and `max()` mathematical
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functions. For those unfamiliar, these functions work a lot like `calc()`,
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except they return the minimum or maximum of a series of values. For example,
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you can write `width: max(50%, 100px)` to make your element either 50% of the
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parent's width or 100px wide, whichever is greater.
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Because Sass has its own functions named `min()` and `max()`, it was difficult
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to use these CSS functions... until now. Dart Sass 1.11 will intelligently
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decide whether to use the plain CSS functions or the built-in Sass functions
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based on whether or not you're passing in dynamic Sass values. For example:
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* The Sass function will be called if you pass a variable, like `max($width,
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100px)`.
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* The Sass function will be called if you call another Sass function, like
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`max(compute-width(), 100px)`.
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* It will compile to a plain CSS function if you just use plain CSS numbers,
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like `max(50% + 10px, 100px)`.
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* It will still compile to a plain CSS function even if you use interpolation,
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like `max(50% + #{$width / 2}, #{$width})`.
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This preserves backwards-compatibility with existing uses of the Sass functions,
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while also users to use the CSS functions the same way they would in plain CSS.
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This feature isn't yet implemented in
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[LibSass](https://github.com/sass/libsass/issues/2701) or [Ruby
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Sass](https://github.com/sass/ruby-sass/issues/77).
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### Range-Format Media Queries
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CSS Media Queries Level 4 defines a [range
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syntax](https://www.w3.org/TR/mediaqueries-4/#mq-range-context) for defining
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certain media queries:
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```css
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@media (width > 500px) {
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/* ... */
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}
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```
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Dart Sass 1.11 adds support for this syntax. It works just like existing media
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query support: you can either use interpolation or plain Sass expressions to
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inject Sass logic into the query, and they can still be nested.
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```scss
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@media (width > $width) {
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@media (height < #{$height}) {
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/* ... */
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}
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}
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```
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This feature isn't yet implemented in
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[LibSass](https://github.com/sass/libsass/issues/2698) or [Ruby
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Sass](https://github.com/sass/ruby-sass/issues/75).
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### Normalized Identifier Escapes
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The last compatibility improvement is a bit of an edge case, but it's still
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worth mentioning: the way Sass parses escapes in identifiers has been improved
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to better match the CSS spec.
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Escapes are now normalized to a standard format, which means that (for example)
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`éclair` and `\E9clair` are parsed to the same value (in this case, `éclair`).
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Prior to this change, if an escape was written, it would always be preserved
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as-is, so `str-length(\E9clair)` would return `8` even though that identifier
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means exactly the same thing to CSS as `éclair`.
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We don't anticipate this affecting many users, but we always strive to bring
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Sass as close to the semantics of CSS as possible. This is a small but important
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step on that path.
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This feature isn't yet implemented in
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[LibSass](https://github.com/sass/libsass/issues/2700) or [Ruby
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Sass](https://github.com/sass/ruby-sass/issues/76).
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