no-duplicate-selectors
Disallow duplicate selectors.
.foo {} .bar {} .foo {}
/** ↑ ↑
* These duplicates */
This rule checks for two types of duplication:
- Duplication of a single selector with a rule's selector list, e.g.
a, b, a {}
. - Duplication of a selector list within a stylesheet, e.g.
a, b {} a, b {}
. Duplicates are found even if the selectors come in different orders or have different spacing, e.g.a d, b > c {} b>c, a d {}
.
The same selector is allowed to repeat in the following circumstances:
- It is used in different selector lists, e.g.
a {} a, b {}
. - The duplicates are determined to originate in different stylesheets, e.g. you have concatenated or compiled files in a way that produces sourcemaps for PostCSS to read, e.g. postcss-import.
- The duplicates are in rules with different parent nodes, e.g. inside and outside of a media query.
This rule resolves nested selectors. So a b {} a { & b {} }
counts as a problem, because the resolved selectors end up with a duplicate.
Options
true
The following patterns are considered problems:
.foo,
.bar,
.foo {}
.foo {}
.bar {}
.foo {}
.foo .bar {}
.bar {}
.foo .bar {}
@media (min-width: 10px) {
.foo {}
.foo {}
}
.foo, .bar {}
.bar, .foo {}
a .foo, b + .bar {}
b+.bar,
a
.foo {}
a b {}
a {
& b {}
}
The following patterns are not considered problems:
.foo {}
@media (min-width: 10px) {
.foo {}
}
.foo {
.foo {}
}
.foo {}
.bar {}
.foo .bar {}
.bar .foo {}
a b {}
a {
& b,
& c {}
}
Optional secondary options
disallowInList: true | false
(default: false
)
This option will also disallow duplicate selectors within selector lists.
For example, with true
.
The following patterns are considered problems:
input, textarea {
border: 2px;
}
textarea {
border: 1px;
}