audit: detect repeated CSS rules (fixes #20)

README.md

@@ -121,6 +121,9 @@ npm run css-audit -- v5.5/**/* --recommended
   - Places where `display: none` is used
 - `typography`
   - A collection of information about various typography-related properties
+- `repeated-rules`
+  - Detects duplicate `property: value` pairs across different selectors
+  - Example: both `.foo` and `.bar` using `border: 1px solid red;`  
 
 ## Technical details
 

src/audits/repeated-rules.js

@@ -0,0 +1,25 @@
+module.exports = {
+	name: "repeated-rules",
+	description: "Detect repeated CSS property/value pairs across selectors",
+
+	run: (astRoot, result) => {
+		const seen = new Map();
+		const repeated = [];
+
+		// Walk through all rules in the CSS AST
+		astRoot.walkDecls((decl) => {
+			const rule = `${decl.prop}: ${decl.value}`;
+			if (seen.has(rule)) {
+				repeated.push(rule);
+			} else {
+				seen.set(rule, decl.parent.selector);
+			}
+		});
+
+		if (repeated.length > 0) {
+			result.warn(
+				`Repeated rules found: ${[...new Set(repeated)].join(", ")}`
+			);
+		}
+	},
+};

src/run.js

@@ -30,6 +30,10 @@ const runAudits = ( cssFiles ) => {
 	if ( getArg( '--alphas' ) ) {
 		audits.push( require( './audits/alphas' )( cssFiles ) );
 	}
+	if ( runAll || getArg( '--repeated-rules' ) ) {
+	    audits.push( require( './audits/repeated-rules' )( cssFiles ) );
+    }
+
 
 	const propertyValues = getArg( '--property-values' );
 	const isPropertyValuesArray =