Sort classes using position of first matching rule (#11504)

* Refactor

* Sort based on first occurence of a candidate

This primarily affects components and utilities which contain multiple matched classes

* Simplify

* Update changelog

* Update

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ensure `repeating-conic-gradient` is detected as an image ([#11180](https://github.com/tailwindlabs/tailwindcss/pull/11180))
 - Move unknown pseudo-elements outside of `:is` by default ([#11345](https://github.com/tailwindlabs/tailwindcss/pull/11345))
 - Escape animation names when prefixes contain special characters ([#11470](https://github.com/tailwindlabs/tailwindcss/pull/11470))
+- Sort classes using position of first matching rule ([#11504](https://github.com/tailwindlabs/tailwindcss/pull/11504))
 
 ### Added
 

src/lib/setupContextUtils.js

@@ -949,7 +949,11 @@ function registerPlugins(plugins, context) {
     let idx = BigInt(parasiteUtilities.length)
 
     for (const [, rule] of rules) {
-      sortedClassNames.set(rule.raws.tailwind.candidate, idx++)
+      let candidate = rule.raws.tailwind.candidate
+
+      // When multiple rules match a candidate
+      // always take the position of the first one
+      sortedClassNames.set(candidate, sortedClassNames.get(candidate) ?? idx++)
     }
 
     return classes.map((className) => {

tests/getSortOrder.test.js

@@ -143,3 +143,41 @@ crosscheck(() => {
     }
   })
 })
+
+it('sorts based on first occurence of a candidate / rule', () => {
+  let classes = [
+    ['foo-1 foo', 'foo foo-1'],
+    ['bar', 'bar'],
+    ['foo-1 foo', 'foo foo-1'],
+  ]
+
+  let config = {
+    theme: {},
+    plugins: [
+      function ({ addComponents }) {
+        addComponents({
+          '.foo': { display: 'block' },
+          '.foo-1': { display: 'block' },
+          '.bar': { display: 'block' },
+
+          // This rule matches both the candidate `foo` and `bar`
+          // But when sorting `foo` — we've already got a
+          // position for `foo` so we should use it
+          '.bar .foo': { display: 'block' },
+        })
+      },
+    ],
+  }
+
+  // Same context, different class lists
+  let context = createContext(resolveConfig(config))
+  for (const [input, output] of classes) {
+    expect(defaultSort(context.getClassOrder(input.split(' ')))).toEqual(output)
+  }
+
+  // Different context, different class lists
+  for (const [input, output] of classes) {
+    context = createContext(resolveConfig(config))
+    expect(defaultSort(context.getClassOrder(input.split(' ')))).toEqual(output)
+  }
+})