fix(no-unused-class-name): detect duplicated class names (#1260)

Author: tbashiyy

.changeset/dry-colts-open.md

@@ -0,0 +1,5 @@
+---
+'eslint-plugin-svelte': patch
+---
+
+fix(no-unused-class-name): detect duplicated class names

packages/eslint-plugin-svelte/src/rules/no-unused-class-name.ts

@@ -36,7 +36,10 @@ export default createRule('no-unused-class-name', {
 			return {};
 		}
 		const allowedClassNames = context.options[0]?.allowedClassNames ?? [];
-		const classesUsedInTemplate: Record<string, AST.SourceLocation> = {};
+		const classesUsedInTemplate: {
+			className: string;
+			loc: AST.SourceLocation;
+		}[] = [];
 
 		return {
 			SvelteElement(node) {
@@ -45,7 +48,7 @@ export default createRule('no-unused-class-name', {
 				}
 				const classes = node.startTag.attributes.flatMap(findClassesInAttribute);
 				for (const className of classes) {
-					classesUsedInTemplate[className] = node.startTag.loc;
+					classesUsedInTemplate.push({ className, loc: node.startTag.loc });
 				}
 			},
 			'Program:exit'() {
@@ -57,15 +60,16 @@ export default createRule('no-unused-class-name', {
 					styleContext.status === 'success'
 						? findClassesInPostCSSNode(styleContext.sourceAst, sourceCode.parserServices)
 						: [];
-				for (const className in classesUsedInTemplate) {
+
+				for (const { className, loc } of classesUsedInTemplate) {
 					if (
 						!allowedClassNames.some((allowedClassName: string) =>
 							toRegExp(allowedClassName).test(className)
 						) &&
 						!classesUsedInStyle.includes(className)
 					) {
 						context.report({
-							loc: classesUsedInTemplate[className],
+							loc,
 							message: `Unused class "${className}".`
 						});
 					}

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unused-class-name/invalid/duplicated-class-name-errors.yaml

@@ -0,0 +1,8 @@
+- message: Unused class "div-class".
+  line: 1
+  column: 1
+  suggestions: null
+- message: Unused class "div-class".
+  line: 3
+  column: 1
+  suggestions: null

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unused-class-name/invalid/duplicated-class-name-input.svelte

@@ -0,0 +1,3 @@
+<div class="div-class">Hello</div>
+
+<span class="div-class">World!</span>