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feat(linter): implement
NoUnmatchableAnbSelector
(#2706)
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crates/biome_css_analyze/src/lint/nursery/no_unmatchable_anb_selector.rs
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use biome_analyze::{context::RuleContext, declare_rule, Ast, Rule, RuleDiagnostic, RuleSource}; | ||
use biome_console::markup; | ||
use biome_css_syntax::{ | ||
AnyCssPseudoClassNth, CssPseudoClassFunctionSelectorList, CssPseudoClassNthSelector, | ||
}; | ||
use biome_rowan::{AstNode, SyntaxNodeCast}; | ||
|
||
declare_rule! { | ||
/// Disallow unmatchable An+B selectors. | ||
/// | ||
/// Selectors that always evaluate to 0 will not match any elements. | ||
/// For more details about the An+B syntax, see: | ||
/// https://www.w3.org/TR/css-syntax-3/#anb-microsyntax | ||
/// | ||
/// ## Examples | ||
/// | ||
/// ### Invalid | ||
/// | ||
/// ```css,expect_diagnostic | ||
/// a:nth-child(0) {} | ||
/// ``` | ||
/// | ||
/// ```css,expect_diagnostic | ||
/// a:nth-last-child(0n) {} | ||
/// ``` | ||
/// | ||
/// ```css,expect_diagnostic | ||
/// a:nth-of-type(0n+0) {} | ||
/// ``` | ||
/// | ||
/// ```css,expect_diagnostic | ||
/// a:nth-last-of-type(0 of a) {} | ||
/// ``` | ||
/// | ||
/// ### Valid | ||
/// | ||
/// ```css | ||
/// a:nth-child(1) {} | ||
/// ``` | ||
/// | ||
/// ```css | ||
/// a:nth-last-child(1n) {} | ||
/// ``` | ||
/// | ||
/// ```css | ||
/// a:nth-of-type(1n+0) {} | ||
/// ``` | ||
/// | ||
/// ```css | ||
/// a:nth-last-of-type(1 of a) {} | ||
/// ``` | ||
/// | ||
pub NoUnmatchableAnbSelector { | ||
version: "next", | ||
name: "noUnmatchableAnbSelector", | ||
recommended: true, | ||
sources: &[RuleSource::Stylelint("selector-anb-no-unmatchable")], | ||
} | ||
} | ||
|
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impl Rule for NoUnmatchableAnbSelector { | ||
type Query = Ast<CssPseudoClassNthSelector>; | ||
type State = CssPseudoClassNthSelector; | ||
type Signals = Option<Self::State>; | ||
type Options = (); | ||
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fn run(ctx: &RuleContext<Self>) -> Option<Self::State> { | ||
let node = ctx.query(); | ||
let nth = node.nth().ok()?; | ||
if is_unmatchable(&nth) && !is_within_not_pseudo_class(&nth) { | ||
return Some(node.clone()); | ||
} | ||
None | ||
} | ||
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fn diagnostic(_: &RuleContext<Self>, node: &Self::State) -> Option<RuleDiagnostic> { | ||
let span = node.range(); | ||
Some( | ||
RuleDiagnostic::new( | ||
rule_category!(), | ||
span, | ||
markup! { | ||
"This selector will never match any elements." | ||
}, | ||
) | ||
.note(markup! { | ||
"Avoid using An+B selectors that always evaluate to 0." | ||
}).note(markup! { | ||
"For more details, see "<Hyperlink href="https://www.w3.org/TR/css-syntax-3/#anb-microsyntax">"the official spec for An+B selectors"</Hyperlink>"." | ||
}) | ||
) | ||
} | ||
} | ||
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fn is_unmatchable(nth: &AnyCssPseudoClassNth) -> bool { | ||
match nth { | ||
AnyCssPseudoClassNth::CssPseudoClassNthIdentifier(_) => false, | ||
AnyCssPseudoClassNth::CssPseudoClassNth(nth) => { | ||
let coefficient = nth.value(); | ||
let constant = nth.offset(); | ||
match (coefficient, constant) { | ||
(Some(a), Some(b)) => a.text() == "0" && b.text() == "0", | ||
(Some(a), None) => a.text() == "0", | ||
_ => false, | ||
} | ||
} | ||
AnyCssPseudoClassNth::CssPseudoClassNthNumber(nth) => nth.text() == "0", | ||
} | ||
} | ||
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// Check if the nth selector is effective within a `not` pseudo class | ||
// Example: a:not(:nth-child(0)) returns true | ||
// a:not(:not(:nth-child(0))) returns false | ||
fn is_within_not_pseudo_class(node: &AnyCssPseudoClassNth) -> bool { | ||
let number_of_not = node | ||
.syntax() | ||
.ancestors() | ||
.filter_map(|n| n.cast::<CssPseudoClassFunctionSelectorList>()) | ||
.filter_map(|n| n.name().ok()) | ||
.filter(|n| n.text() == "not") | ||
.count(); | ||
number_of_not % 2 == 1 | ||
} |
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crates/biome_css_analyze/tests/specs/nursery/noUnmatchableAnbSelector/invalid.css
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a:nth-child(0) {} | ||
a:nth-child(0n) {} | ||
a:nth-child(+0n) {} | ||
a:nth-child(-0n) {} | ||
a:nth-child(0n+0) {} | ||
a:nth-child(0n-0) {} | ||
a:nth-child(-0n-0) {} | ||
a:nth-child(0 of a) {} | ||
a:nth-child(0), a:nth-child(1) {} | ||
a:nth-last-child(0) {} | ||
a:nth-of-type(0) {} | ||
a:nth-last-of-type(0) {} | ||
a:nth-child(0n):nth-child(-n+5) {} | ||
a:nth-last-child(0),a:nth-last-child(n+5) ~ li {} |
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