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, itwould pull all the declarations to the beginning of the rule to avoidduplicating the outer selector more than necessary. For example:
CSS Output
.example{
color: red;
font-weight: normal;
}
.example--serious{
font-weight: bold;
}
WhenplainCSS Nesting was first introduced, it behaved the same way. However,after some consideration,theCSS working group decided it made more sense tomake the declarations apply in the order they appeared in the document, like so:
CSS Output
.example{
color: red;
}
.example--serious{
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 declarationsafter nested rules is currently deprecated in Sass, inorder to notify users of the upcoming change and give them time to make theirstylesheets compatible with it. In a future release, Dart Sass will change tomatch the ordering produced by plainCSS nesting.
If you want to opt into the newCSS semantics early, you can wrap your nesteddeclarations in& {}:
PlaygroundSCSS Syntax
.example{
color: red;
&--serious{
font-weight: bold;
}
&{
font-weight: normal;
}
}
CSS Output
.example{
color: red;
}
.example--serious{
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 deprecationwarnings 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 ofdeprecation warning five times before it silences additional warnings. Thishelps ensure that users know when they need to be aware of an upcoming breakingchange without creating an overwhelming amount of console noise.
If you run Sass in verbose mode instead, it will printevery deprecationwarning it encounters. This can be useful for tracking the remaining work to bedone when fixing deprecations. You can enable verbose mode usingthe--verbose flag on the command line, ortheverbose option in the JavaScript API.
⚠️ Heads up!
When running from theJSAPI, Sass doesn’t share any information acrosscompilations, so by default it’ll print five warnings foreach stylesheetthat’s compiled. However, you can fix this by writing (or asking the author ofyour favorite framework’s Sass plugin to write) acustomLogger that onlyprints 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 doanything about. You can silence deprecation warnings from dependencies whilestill printing them for your app usingthe--quiet-deps flag on the command line, orthequietDeps option in the JavaScript API.
For the purposes of this flag, a "dependency" is any stylesheet that’s not justa series of relative loads from the entrypoint stylesheet. This means anythingthat 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 cansilence warnings for that specific deprecation usingthe--silence-deprecation flag on the command line, orthesilenceDeprecations option in the JavaScript API.