mirror of
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72 lines
2.9 KiB
Markdown
72 lines
2.9 KiB
Markdown
A [Dart](https://www.dartlang.org) implementation of
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[Sass](http://sass-lang.com/).
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## Using Dart Sass
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Dart Sass isn't ready for distribution yet, but it's possible to test it out by
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running from source. This assumes you've already checked out this repository.
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1. [Install Dart](https://www.dartlang.org/install). If you download it
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manually, make sure the SDK's `bin` directory is on your `PATH`.
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2. In this repository, run `pub get`. This will install Dart Sass's
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dependencies.
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3. Run `dart bin/sass.dart path/to/file.scss`.
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That's it!
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## Goals
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Dart Sass is intended to eventually replace Ruby Sass as the canonical
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implementation of the Sass language. It has a number of advantages:
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* It's fast. The Dart VM is highly optimized, and getting faster all the time
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(for the latest performance numbers, see [`perf.md`][perf]). It's much faster
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than Ruby, and not too far away from C.
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* It's portable. The Dart VM has no external dependencies and can compile
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applications into standalone snapshot files, so a fully-functional Dart Sass
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could be distributed as only three files (the VM, the snapshot, and a wrapper
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script). Dart can also be compiled to JavaScript, which would make it easy to
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distribute Sass through NPM or other JS package managers.
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* It's friendlier to contributors. Dart is substantially easier to learn than
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Ruby, and many Sass users in Google in particular are already familiar with
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it. More contributors translates to faster, more consistent development.
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[perf]: https://github.com/sass/dart-sass/blob/master/perf.md
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## Behavioral Differences
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There are a few intentional behavioral differences between Dart Sass and Ruby
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Sass. These are generally places where Ruby Sass has an undesired behavior, and
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it's substantially easier to implement the correct behavior than it would be to
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implement compatible behavior. These should all have tracking bugs against Ruby
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Sass to update the reference behavior.
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1. `@extend` only accepts simple selectors, as does the second argument of
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`selector-extend()`. See [issue 1599][].
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2. Subject selectors are not supported. See [issue 1126][].
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3. Pseudo selector arguments are parsed as `<declaration-value>`s rather than
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having a more limited custom parsing. See [issue 2120][].
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4. The numeric precision is set to 10. See [issue 1122][].
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5. The indented syntax parser is more flexible: it doesn't require consistent
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indentation across the whole document. This doesn't have an issue yet; I need
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to talk to Chris to determine if it's actually the right way forward.
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6. Colors do not support channel-by-channel arithmetic. See [issue 2144][].
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[issue 1599]: https://github.com/sass/sass/issues/1599
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[issue 1126]: https://github.com/sass/sass/issues/1126
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[issue 2120]: https://github.com/sass/sass/issues/2120
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[issue 1122]: https://github.com/sass/sass/issues/1122
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[issue 2144]: https://github.com/sass/sass/issues/2144
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Disclaimer: this is not an official Google product.
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