#136: Remove duplicates from ordered classNames instead of unordered classNames

Author: mpsijm

lib/rules/classnames-order.js

@@ -300,10 +300,6 @@ module.exports = {
         return;
       }
 
-      if (removeDuplicates) {
-        removeDuplicatesFromClassnamesAndWhitespaces(classNames, whitespaces, headSpace, tailSpace);
-      }
-
       let orderedClassNames;
 
       // Sorting
@@ -329,6 +325,10 @@ module.exports = {
         orderedClassNames = prependCustom ? [...mergedExtras, ...flatted] : [...flatted, ...mergedExtras];
       }
 
+      if (removeDuplicates) {
+        removeDuplicatesFromClassnamesAndWhitespaces(orderedClassNames, whitespaces, headSpace, tailSpace);
+      }
+
       // Generates the validated/sorted attribute value
       let validatedClassNamesValue = '';
       for (let i = 0; i < orderedClassNames.length; i++) {

lib/util/removeDuplicatesFromClassnamesAndWhitespaces.js

@@ -1,20 +1,18 @@
 'use strict';
 
-function removeDuplicatesFromClassnamesAndWhitespaces(classNames, whitespaces, headSpace, tailSpace) {
-  const uniqueSet = new Set(classNames);
-  if (uniqueSet.size === classNames.length) {
-    return;
-  }
+function removeDuplicatesFromClassnamesAndWhitespaces(orderedClassNames, whitespaces, headSpace, tailSpace) {
+  let previous = orderedClassNames[0];
   const offset = (!headSpace && !tailSpace) || tailSpace ? -1 : 0;
-  uniqueSet.forEach((cls) => {
-    let duplicatedInstances = classNames.filter((el) => el === cls).length - 1;
-    while (duplicatedInstances > 0) {
-      const idx = classNames.lastIndexOf(cls);
-      classNames.splice(idx, 1);
-      whitespaces.splice(idx + offset, 1);
-      duplicatedInstances--;
+  for (let i = 1; i < orderedClassNames.length; i++) {
+    const cls = orderedClassNames[i];
+    // This function assumes that the list of classNames is ordered, so just comparing to the previous className is enough
+    if (cls === previous) {
+      orderedClassNames.splice(i, 1);
+      whitespaces.splice(i + offset, 1);
+      i--;
     }
-  });
+    previous = cls;
+  }
 }
 
 module.exports = removeDuplicatesFromClassnamesAndWhitespaces;

tests/lib/rules/classnames-order.js

@@ -382,17 +382,17 @@ ruleTester.run("classnames-order", rule, {
     },
     {
       code: `<div class="w-12  lg:w-6   w-12">Single line dups + no head/tail spaces</div>`,
-      output: `<div class="w-12  lg:w-6">Single line dups + no head/tail spaces</div>`,
+      output: `<div class="w-12   lg:w-6">Single line dups + no head/tail spaces</div>`,
       errors: errors,
     },
     {
       code: `<div class=" w-12  lg:w-6   w-12">Single dups line + head spaces</div>`,
-      output: `<div class=" w-12  lg:w-6">Single dups line + head spaces</div>`,
+      output: `<div class=" w-12   lg:w-6">Single dups line + head spaces</div>`,
       errors: errors,
     },
     {
       code: `<div class="w-12  lg:w-6   w-12 ">Single line dups + tail spaces</div>`,
-      output: `<div class="w-12  lg:w-6 ">Single line dups + tail spaces</div>`,
+      output: `<div class="w-12   lg:w-6 ">Single line dups + tail spaces</div>`,
       errors: errors,
     },
     {