Breaking Change: Mixed Declarations
CSS is changing the way it handles declarations mixed with nested rules, and we want to make sure Sass matches its behavior.
The Story So FarThe Story So Far permalink
Historically, if you mixed together nested rules and declarations in Sass, it would pull all the declarations to the beginning of the rule to avoid duplicating the outer selector more than necessary. For example:
CSS Output
.example {
color: red;
font-weight: normal;
}
.example a {
font-weight: bold;
}
When plain CSS Nesting was first introduced, it behaved the same way. However, after some consideration, the CSS working group decided it made more sense to make the declarations apply in the order they appeared in the document, like so:
CSS Output
.example {
color: red;
}
.example a {
font-weight: bold;
}
.example {
font-weight: normal;
}
Deprecating the Old WayDeprecating the Old Way permalink
- Dart Sass
- since 1.77.7
- LibSass
- ✗
- Ruby Sass
- ✗
The use of declarations after nested rules is currently deprecated in Sass, in order to notify users of the upcoming change and give them time to make their stylesheets compatible with it. In a future release, Dart Sass will change to match the ordering produced by plain CSS nesting.
If you want to opt into the new CSS semantics early, you can wrap your nested
declarations in & {}:
CSS Output
.example {
color: red;
}
.example a {
font-weight: bold;
}
.example {
font-weight: normal;
}
Can I Silence the Warnings?Can I Silence the Warnings? permalink
Sass provides a powerful suite of options for managing which deprecation warnings you see and when.
Terse and Verbose ModeTerse and Verbose Mode permalink
By default, Sass runs in terse mode, where it will only print each type of deprecation warning five times before it silences additional warnings. This helps ensure that users know when they need to be aware of an upcoming breaking change without creating an overwhelming amount of console noise.
If you run Sass in verbose mode instead, it will print every deprecation
warning it encounters. This can be useful for tracking the remaining work to be
done when fixing deprecations. You can enable verbose mode using
the --verbose flag on the command line, or
the verbose option in the JavaScript API.
⚠️ Heads up!
When running from the JS API, Sass doesn’t share any information across
compilations, so by default it’ll print five warnings for each stylesheet
that’s compiled. However, you can fix this by writing (or asking the author of
your favorite framework’s Sass plugin to write) a custom Logger that only
prints five errors per deprecation and can be shared across multiple compilations.
Silencing Deprecations in DependenciesSilencing Deprecations in Dependencies permalink
Sometimes, your dependencies have deprecation warnings that you can’t do
anything about. You can silence deprecation warnings from dependencies while
still printing them for your app using
the --quiet-deps flag on the command line, or
the quietDeps option in the JavaScript API.
For the purposes of this flag, a "dependency" is any stylesheet that’s not just a series of relative loads from the entrypoint stylesheet. This means anything that comes from a load path, and most stylesheets loaded through custom importers.
Silencing Specific DeprecationsSilencing Specific Deprecations permalink
If you know that one particular deprecation isn’t a problem for you, you can
silence warnings for that specific deprecation using
the --silence-deprecation flag on the command line, or
the silenceDeprecations option in the JavaScript API.