Use existing prefixSelector function

__tests__/applyAtRule.test.js

@@ -216,3 +216,29 @@ test('you can apply utility classes without using the given prefix', () => {
     expect(result.warnings().length).toBe(0)
   })
 })
+
+// test('you can apply utility classes without using the given prefix when using a function for the prefix', () => {
+//   const input = `
+//     .foo { @apply .tw-mt-4 .mb-4; }
+//   `
+
+//   const expected = `
+//     .foo { margin-top: 1rem; margin-bottom: 1rem; }
+//   `
+
+//   const config = {
+//     ...defaultConfig,
+//     options: {
+//       ...defaultConfig.options,
+//       prefix: selector => {
+//         return 'tw-'
+//       },
+//     },
+//     experiments: { shadowLookup: true },
+//   }
+
+//   return run(input, config, generateUtilities(config, [])).then(result => {
+//     expect(result.css).toEqual(expected)
+//     expect(result.warnings().length).toBe(0)
+//   })
+// })

src/lib/substituteClassApplyAtRules.js

@@ -1,6 +1,7 @@
 import _ from 'lodash'
 import postcss from 'postcss'
 import escapeClassName from '../util/escapeClassName'
+import prefixSelector from '../util/prefixSelector'
 
 function buildClassTable(css) {
   const classTable = {}
@@ -35,7 +36,7 @@ function findClass(classToApply, classTable, shadowLookup, prefix, onError) {
   if (_.isEmpty(matches)) {
     if (_.isEmpty(shadowLookup)) {
       if (prefix) {
-        classToApply = '.' + prefix + classToApply.substr(1)
+        classToApply = prefixSelector(prefix, classToApply)
         matches = _.get(classTable, classToApply, [])
         if (_.isEmpty(matches)) {
           if (_.isEmpty(shadowLookup)) {