Breaking Change: Mixed Declarations

CSS changed the way it handles declarations mixed with nested rules, and we made sure Sass matched 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:

Playground

SCSS Syntax

.example {
  color: red;

  &--serious {
    font-weight: bold;
  }

  font-weight: normal;
}
Playground

Sass Syntax

.example
  color: red

  &--serious
    font-weight: bold


  font-weight: normal

CSS Output

.example {
  color: red;
  font-weight: normal;
}

.example--serious {
  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:

Playground

SCSS Syntax

.example {
  color: red;

  &--serious {
    font-weight: bold;
  }

  font-weight: normal;
}
Playground

Sass 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;
}

Deprecating the Old WayDeprecating the Old Way permalink

Compatibility:
Dart Sass
since 1.77.7
LibSass
✗
Ruby Sass
✗

The use of declarations after nested rules was first deprecated in order to notify users of the upcoming change and give them time to make their stylesheets compatible with it.

Users who wanted to opt into the new CSS semantics early could wrap their nested declarations in & {}:

Playground

SCSS Syntax

.example {
  color: red;

  &--serious {
    font-weight: bold;
  }

  & {
    font-weight: normal;
  }
}
Playground

Sass 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 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.

The New WayThe New Way permalink

Compatibility:
Dart Sass
since 1.92.0
LibSass
✗
Ruby Sass
✗

Modern versions of Sass behave the same way as plain CSS: declarations are emitted in the same order they’re written, even if that involves duplicating the rule that contains them to account for interleaved rules. The same is true for loud (/* */-style) comments and at-rules without children.