Fix cannot read properties of undefined (reading 'modifier') (#9656)

* fix #9655

* update changelog

* add test for making sure calling variantFn doesn't crash

* make it behave as-if modifiers didn't exist

Co-authored-by: Robin Malfait <malfait.robin@gmail.com>

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ensure configured `font-feature-settings` are included in Preflight ([#9707](https://github.com/tailwindlabs/tailwindcss/pull/9707))
 - Fix fractional values not being parsed properly inside arbitrary properties ([#9705](https://github.com/tailwindlabs/tailwindcss/pull/9705))
 - Fix incorrect selectors when using `@apply` in selectors with combinators and pseudos ([#9722](https://github.com/tailwindlabs/tailwindcss/pull/9722))
+- Fix cannot read properties of undefined (reading 'modifier') ([#9656](https://github.com/tailwindlabs/tailwindcss/pull/9656))
 
 ## [3.2.1] - 2022-10-21
 

src/lib/setupContextUtils.js

@@ -528,7 +528,7 @@ function buildPluginApi(tailwindConfig, context, { variantList, variantMap, offs
       variantFunctions = [].concat(variantFunctions).map((variantFunction) => {
         if (typeof variantFunction !== 'string') {
           // Safelist public API functions
-          return (api) => {
+          return (api = {}) => {
             let { args, modifySelectors, container, separator, wrap, format } = api
             let result = variantFunction(
               Object.assign(
@@ -581,11 +581,13 @@ function buildPluginApi(tailwindConfig, context, { variantList, variantMap, offs
 
         api.addVariant(
           isSpecial ? `${variant}${key}` : `${variant}-${key}`,
-          ({ args, container }) =>
-            variantFn(
+          ({ args, container }) => {
+            return variantFn(
               value,
-              modifiersEnabled ? { modifier: args.modifier, container } : { container }
-            ),
+              modifiersEnabled ? { modifier: args?.modifier, container } : { container }
+            )
+          },
+
           {
             ...options,
             value,
@@ -601,13 +603,13 @@ function buildPluginApi(tailwindConfig, context, { variantList, variantMap, offs
       api.addVariant(
         variant,
         ({ args, container }) => {
-          if (args.value === sharedState.NONE && !hasDefault) {
+          if (args?.value === sharedState.NONE && !hasDefault) {
             return null
           }
 
           return variantFn(
-            args.value === sharedState.NONE ? options.values.DEFAULT : args.value,
-            modifiersEnabled ? { modifier: args.modifier, container } : { container }
+            args?.value === sharedState.NONE ? options.values.DEFAULT : args?.value,
+            modifiersEnabled ? { modifier: args?.modifier, container } : { container }
           )
         },
         {

tests/match-variants.test.js

@@ -1,3 +1,6 @@
+import resolveConfig from '../src/public/resolve-config'
+import { createContext } from '../src/lib/setupContextUtils'
+
 import { run, html, css } from './util/run'
 
 test('partial arbitrary variants', () => {
@@ -788,3 +791,56 @@ it('should be possible to use `undefined` as a DEFAULT value', () => {
     `)
   })
 })
+
+it('should be possible to use `undefined` as a DEFAULT value', () => {
+  let config = {
+    content: [
+      {
+        raw: html`
+          <div>
+            <div class="foo:underline"></div>
+          </div>
+        `,
+      },
+    ],
+    corePlugins: { preflight: false },
+    plugins: [
+      ({ matchVariant }) => {
+        matchVariant('foo', (value) => `.foo${value === undefined ? '-good' : '-bad'} &`, {
+          values: { DEFAULT: undefined },
+        })
+      },
+    ],
+  }
+
+  let input = css`
+    @tailwind utilities;
+  `
+
+  return run(input, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(css`
+      .foo-good .foo\:underline {
+        text-decoration-line: underline;
+      }
+    `)
+  })
+})
+
+it('should not break things', () => {
+  let config = {}
+
+  let context = createContext(resolveConfig(config))
+  let [[, fn]] = context.variantMap.get('group')
+
+  let format
+
+  expect(
+    fn({
+      format(input) {
+        format = input
+      },
+    })
+  ).toBe(undefined)
+
+  expect(format).toBe(':merge(.group) &')
+})