feat(biome_css_analyze): implement noDescendingSpecificity (#4097)

crates/biome_css_analyze/src/lint/nursery.rs

@@ -2,6 +2,7 @@
 
 use biome_analyze::declare_lint_group;
 
+pub mod no_descending_specificity;
 pub mod no_duplicate_custom_properties;
 pub mod no_irregular_whitespace;
 pub mod no_missing_var_function;
@@ -13,6 +14,7 @@ declare_lint_group! {
     pub Nursery {
         name : "nursery" ,
         rules : [
+            self :: no_descending_specificity :: NoDescendingSpecificity ,
             self :: no_duplicate_custom_properties :: NoDuplicateCustomProperties ,
             self :: no_irregular_whitespace :: NoIrregularWhitespace ,
             self :: no_missing_var_function :: NoMissingVarFunction ,

crates/biome_css_analyze/src/lint/nursery/no_descending_specificity.rs

@@ -0,0 +1,203 @@
+use rustc_hash::{FxHashMap, FxHashSet};
+
+use biome_analyze::{context::RuleContext, declare_lint_rule, Rule, RuleDiagnostic, RuleSource};
+use biome_console::markup;
+use biome_css_semantic::model::{Rule as CssSemanticRule, RuleId, SemanticModel, Specificity};
+use biome_css_syntax::{AnyCssSelector, CssRoot};
+use biome_rowan::TextRange;
+
+use biome_rowan::AstNode;
+
+use crate::services::semantic::Semantic;
+
+declare_lint_rule! {
+    /// Disallow a lower specificity selector from coming after a higher specificity selector.
+    ///
+    /// This rule prohibits placing selectors with lower specificity after selectors with higher specificity.
+    /// By maintaining the order of the source and specificity as consistently as possible, it enhances readability.
+    ///
+    /// ## Examples
+    ///
+    /// ### Invalid
+    ///
+    /// ```css,expect_diagnostic
+    /// b a { color: red; }
+    /// a { color: red; }
+    /// ```
+    ///
+    /// ```css,expect_diagnostic
+    /// a {
+    ///   & > b { color: red; }
+    /// }
+    /// b { color: red; }
+    /// ```
+    ///
+    /// ```css,expect_diagnostic
+    /// :root input {
+    ///     color: red;
+    /// }
+    /// html input {
+    ///     color: red;
+    /// }
+    /// ```
+    ///
+    ///
+    /// ### Valid
+    ///
+    /// ```css
+    /// a { color: red; }
+    /// b a { color: red; }
+    /// ```
+    ///
+    /// ```css
+    /// b { color: red; }
+    /// a {
+    ///   & > b { color: red; }
+    /// }
+    /// ```
+    ///
+    /// ```css
+    /// a:hover { color: red; }
+    /// a { color: red; }
+    /// ```
+    ///
+    /// ```css
+    /// a b {
+    ///     color: red;
+    /// }
+    /// /* This selector is overwritten by the one above it, but this is not an error because the rule only evaluates it as a compound selector */
+    /// :where(a) :is(b) {
+    ///     color: blue;
+    /// }
+    /// ```
+    ///
+    pub NoDescendingSpecificity {
+        version: "next",
+        name: "noDescendingSpecificity",
+        language: "css",
+        recommended: true,
+        sources: &[RuleSource::Stylelint("no-descending-specificity")],
+    }
+}
+
+#[derive(Debug)]
+pub struct DescendingSelector {
+    high: (TextRange, Specificity),
+    low: (TextRange, Specificity),
+}
+/// find tail selector
+/// ```css
+/// a b:hover {
+///   ^^^^^^^
+/// }
+/// ```
+fn find_tail_selector(selector: &AnyCssSelector) -> Option<String> {
+    match selector {
+        AnyCssSelector::CssCompoundSelector(s) => {
+            let simple = s
+                .simple_selector()
+                .map_or(String::new(), |s| s.syntax().text_trimmed().to_string());
+            let sub = s.sub_selectors().syntax().text_trimmed().to_string();
+
+            let last_selector = [simple, sub].join("");
+            Some(last_selector)
+        }
+        AnyCssSelector::CssComplexSelector(s) => {
+            s.right().as_ref().ok().and_then(find_tail_selector)
+        }
+        _ => None,
+    }
+}
+
+/// This function traverses the CSS rules starting from the given rule and checks for selectors that have the same tail selector.
+/// For each selector, it compares its specificity with the previously encountered specificity of the same tail selector.
+/// If a lower specificity selector is found after a higher specificity selector with the same tail selector, it records this as a descending selector.
+fn find_descending_selector(
+    rule: &CssSemanticRule,
+    model: &SemanticModel,
+    visited_rules: &mut FxHashSet<RuleId>,
+    visited_selectors: &mut FxHashMap<String, (TextRange, Specificity)>,
+    descending_selectors: &mut Vec<DescendingSelector>,
+) {
+    if visited_rules.contains(&rule.id) {
+        return;
+    } else {
+        visited_rules.insert(rule.id);
+    };
+
+    for selector in &rule.selectors {
+        let tail_selector = if let Some(s) = find_tail_selector(&selector.original) {
+            s
+        } else {
+            continue;
+        };
+
+        if let Some((last_textrange, last_specificity)) = visited_selectors.get(&tail_selector) {
+            if last_specificity > &selector.specificity {
+                descending_selectors.push(DescendingSelector {
+                    high: (*last_textrange, last_specificity.clone()),
+                    low: (selector.range, selector.specificity.clone()),
+                });
+            }
+        } else {
+            visited_selectors.insert(
+                tail_selector,
+                (selector.range, selector.specificity.clone()),
+            );
+        }
+    }
+
+    for child_id in &rule.child_ids {
+        if let Some(child_rule) = model.get_rule_by_id(*child_id) {
+            find_descending_selector(
+                child_rule,
+                model,
+                visited_rules,
+                visited_selectors,
+                descending_selectors,
+            );
+        }
+    }
+}
+
+impl Rule for NoDescendingSpecificity {
+    type Query = Semantic<CssRoot>;
+    type State = DescendingSelector;
+    type Signals = Vec<Self::State>;
+    type Options = ();
+
+    fn run(ctx: &RuleContext<Self>) -> Self::Signals {
+        let model = ctx.model();
+        let mut visited_rules = FxHashSet::default();
+        let mut visited_selectors = FxHashMap::default();
+        let mut descending_selectors = Vec::new();
+        for rule in model.rules() {
+            find_descending_selector(
+                rule,
+                model,
+                &mut visited_rules,
+                &mut visited_selectors,
+                &mut descending_selectors,
+            );
+        }
+
+        descending_selectors
+    }
+
+    fn diagnostic(_: &RuleContext<Self>, node: &Self::State) -> Option<RuleDiagnostic> {
+        Some(
+            RuleDiagnostic::new(
+                rule_category!(),
+                node.low.0,
+                markup! {
+                    "Descending specificity selector found. This selector specificity is "{node.low.1.to_string()}
+                },
+            ).detail(node.high.0, markup!(
+                "This selector specificity is "{node.high.1.to_string()}
+            ))
+            .note(markup! {
+                    "Descending specificity selector may not applied. Consider rearranging the order of the selectors. See "<Hyperlink href="https://developer.mozilla.org/en-US/docs/Web/CSS/Specificity">"MDN web docs"</Hyperlink>" for more details."
+            }),
+        )
+    }
+}

crates/biome_css_analyze/tests/specs/nursery/noDescendingSpecificity/complex_selector.invalid.css

@@ -0,0 +1,7 @@
+b a {
+    color: red;
+}
+
+a {
+    color: red;
+}

crates/biome_css_analyze/tests/specs/nursery/noDescendingSpecificity/complex_selector.invalid.css.snap

@@ -0,0 +1,40 @@
+---
+source: crates/biome_css_analyze/tests/spec_tests.rs
+expression: complex_selector.invalid.css
+---
+# Input
+```css
+b a {
+    color: red;
+}
+
+a {
+    color: red;
+}
+
+```
+
+# Diagnostics
+```
+complex_selector.invalid.css:5:1 lint/nursery/noDescendingSpecificity ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Descending specificity selector found. This selector specificity is (0, 0, 1)
+
+    3 │ }
+    4 │ 
+  > 5 │ a {
+      │ ^
+    6 │     color: red;
+    7 │ }
+
+  i This selector specificity is (0, 0, 2)
+
+  > 1 │ b a {
+      │ ^^^
+    2 │     color: red;
+    3 │ }
+
+  i Descending specificity selector may not applied. Consider rearranging the order of the selectors. See MDN web docs for more details.
+
+
+```

crates/biome_css_analyze/tests/specs/nursery/noDescendingSpecificity/function_pseudo_selector.invalid.css

@@ -0,0 +1,15 @@
+:is(#a, a) f {
+    color: red;
+}
+
+:is(a, b, c, d) f {
+    color: red;
+}
+
+:is(#fake#fake#fake#fake#fake#fake, *) g {
+    color: red;
+}
+
+:where(*) g {
+    color: red;
+}

crates/biome_css_analyze/tests/specs/nursery/noDescendingSpecificity/function_pseudo_selector.invalid.css.snap

@@ -0,0 +1,73 @@
+---
+source: crates/biome_css_analyze/tests/spec_tests.rs
+expression: function_pseudo_selector.invalid.css
+---
+# Input
+```css
+:is(#a, a) f {
+    color: red;
+}
+
+:is(a, b, c, d) f {
+    color: red;
+}
+
+:is(#fake#fake#fake#fake#fake#fake, *) g {
+    color: red;
+}
+
+:where(*) g {
+    color: red;
+}
+```
+
+# Diagnostics
+```
+function_pseudo_selector.invalid.css:5:1 lint/nursery/noDescendingSpecificity ━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Descending specificity selector found. This selector specificity is (0, 0, 2)
+
+    3 │ }
+    4 │ 
+  > 5 │ :is(a, b, c, d) f {
+      │ ^^^^^^^^^^^^^^^^^
+    6 │     color: red;
+    7 │ }
+
+  i This selector specificity is (1, 0, 1)
+
+  > 1 │ :is(#a, a) f {
+      │ ^^^^^^^^^^^^
+    2 │     color: red;
+    3 │ }
+
+  i Descending specificity selector may not applied. Consider rearranging the order of the selectors. See MDN web docs for more details.
+
+
+```
+
+```
+function_pseudo_selector.invalid.css:13:1 lint/nursery/noDescendingSpecificity ━━━━━━━━━━━━━━━━━━━━━
+
+  ! Descending specificity selector found. This selector specificity is (0, 0, 1)
+
+    11 │ }
+    12 │ 
+  > 13 │ :where(*) g {
+       │ ^^^^^^^^^^^
+    14 │     color: red;
+    15 │ }
+
+  i This selector specificity is (6, 0, 1)
+
+     7 │ }
+     8 │ 
+   > 9 │ :is(#fake#fake#fake#fake#fake#fake, *) g {
+       │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    10 │     color: red;
+    11 │ }
+
+  i Descending specificity selector may not applied. Consider rearranging the order of the selectors. See MDN web docs for more details.
+
+
+```

crates/biome_css_analyze/tests/specs/nursery/noDescendingSpecificity/nested.invalid.css

@@ -0,0 +1,9 @@
+a {
+    & > b {
+        color: red;
+    }
+}
+
+b {
+    color: red;
+}