Don’t prefix classes in arbitrary values for group and peer

src/corePlugins.js

@@ -187,9 +187,13 @@ export let variantPlugins = {
           }
 
           // Basically this but can handle quotes:
-          // result.replace(/&(\S+)?/g, (_, pseudo = '') => a + pseudo + b)
+          // result.replace(/&(\S+)?/g, (_, pseudo = '') => a + `:tw-no-prefix(${pseudo})` + b)
 
-          return result.slice(0, start) + a + result.slice(start + 1, end) + b + result.slice(end)
+          let pseudo = result.slice(start + 1, end)
+
+          pseudo = config('prefix') ? `:tw-no-prefix(${pseudo})` : pseudo
+
+          return result.slice(0, start) + a + pseudo + b + result.slice(end)
         },
         { values: Object.fromEntries(pseudoVariants) }
       )

src/util/prefixSelector.js

@@ -22,6 +22,13 @@ export default function (prefix, selector, prependNegative = false) {
 
   // ast.walk bails too early when returning so it's not usable here
   function prefixClasses(node) {
+    // Here we look for `:tw-no-prefix` which is an *internal-use-only* marker
+    // used to stop traversal so we don't replace any classes inside it
+    if (node.type === 'pseudo' && node.value === ':tw-no-prefix') {
+      node.replaceWith(...node.nodes)
+      return
+    }
+
     // Prefix any classes we find
     if (node.type === 'class') {
       let baseClass = node.value

tests/prefix.test.js

@@ -1,3 +1,4 @@
+import prefixSelector from '../src/util/prefixSelector'
 import { run, html, css, defaults } from './util/run'
 
 test('prefix', () => {
@@ -607,3 +608,42 @@ test('supports non-word prefixes (2)', async () => {
     }
   `)
 })
+
+test('does not prefix arbitrary group/peer classes', async () => {
+  let config = {
+    prefix: 'tw-',
+    content: [
+      {
+        raw: html`
+          <div class="tw-group tw-peer lol">
+            <div class="group-[&.lol]:tw-flex"></div>
+          </div>
+          <div class="peer-[&.lol]:tw-flex"></div>
+        `,
+      },
+    ],
+    corePlugins: { preflight: false },
+  }
+
+  let input = css`
+    @tailwind utilities;
+  `
+
+  const result = await run(input, config)
+
+  expect(result.css).toMatchFormattedCss(css`
+    .tw-group.lol .group-\[\&\.lol\]\:tw-flex,
+    .tw-peer.lol ~ .peer-\[\&\.lol\]\:tw-flex {
+      display: flex;
+    }
+  `)
+})
+
+// Unit tests for prefixSelector
+describe('prefixSelector', () => {
+  it('works', () => {
+    expect(prefixSelector('tw-', '.foo', false)).toBe('.tw-foo')
+    expect(prefixSelector('tw-', '.foo.bar.baz', false)).toBe('.tw-foo.tw-bar.tw-baz')
+    expect(prefixSelector('tw-', '.foo:tw-no-prefix(.bar).baz', false)).toBe('.tw-foo.bar.tw-baz')
+  })
+})