Add bundled v4 fallback

package.json

@@ -72,6 +72,7 @@
     "resolve-from": "^5.0.0",
     "rimraf": "^6.0.1",
     "svelte": "^5.38.2",
+    "tailwindcss": "^4.1.12",
     "tailwindcss-v3": "npm:tailwindcss@^3.4.17",
     "tsup": "^8.5.0",
     "vitest": "^3.2.4"

src/config.ts

@@ -75,7 +75,7 @@ export async function getTailwindConfig(options: ParserOptions): Promise<any> {
   //
   // For the same reasons as the v4 stylesheet, it's important that the config
   // file be resolved relative to the file it's configured in.
-  if (!stylesheet && !mod?.__unstable__loadDesignSystem) {
+  if (!stylesheet && mod && !mod.__unstable__loadDesignSystem) {
     jsConfig = jsConfig ?? findClosestJsConfig(inputDir)
   }
 
@@ -112,14 +112,6 @@ export async function getTailwindConfig(options: ParserOptions): Promise<any> {
     stylesheet ??= `${pkgDir}/theme.css`
   }
 
-  // No stylesheet was given or otherwise found in a local v4 installation
-  // nor was a tailwind config given or found.
-  //
-  // Fallback to v3
-  if (!stylesheet) {
-    return pathToApiMap.remember(null, () => loadV3(null, null))
-  }
-
   return pathToApiMap.remember(`${pkgDir}:${stylesheet}`, () => loadV4(mod, stylesheet))
 }
 

src/resolve.ts

@@ -9,7 +9,7 @@ const esmResolver = ResolverFactory.createResolver({
   fileSystem,
   useSyncFileSystemCalls: true,
   extensions: ['.mjs', '.js'],
-  mainFields: ['module'],
+  mainFields: ['module', 'main'],
   conditionNames: ['node', 'import'],
 })
 

src/versions/v4.ts

@@ -1,11 +1,10 @@
-// @ts-check
 import * as fs from 'fs/promises'
 import * as path from 'path'
 import { pathToFileURL } from 'url'
 import { createJiti, type Jiti } from 'jiti'
-import postcss from 'postcss'
+import { __unstable__loadDesignSystem } from 'tailwindcss'
 // @ts-ignore
-import postcssImport from 'postcss-import'
+import themeCss from 'tailwindcss/theme.css'
 import { resolveCssFrom, resolveJsFrom } from '../resolve'
 import type { UnifiedApi } from '../types'
 
@@ -44,9 +43,7 @@ interface ApiV4 {
 export async function loadV4(mod: ApiV4 | null, stylesheet: string | null): Promise<UnifiedApi> {
   // This is not Tailwind v4
   if (!mod || !mod.__unstable__loadDesignSystem) {
-    throw new Error('TODO')
-    // TODO
-    // mod = (await import('tailwindcss-v4')) as ApiV4
+    mod = (await import('tailwindcss')) as ApiV4
   }
 
   // Create a Jiti instance that can be used to load plugins and config files
@@ -65,9 +62,7 @@ export async function loadV4(mod: ApiV4 | null, stylesheet: string | null): Prom
   } else {
     importBasePath = process.cwd()
     stylesheet = path.join(importBasePath, 'fake.css')
-
-    // TODO: bundled theme.css file?
-    css = ''
+    css = themeCss
   }
 
   // Load the design system and set up a compatible context object that is

tests/format.test.ts

@@ -26,6 +26,12 @@ describe('other', () => {
 
     expect(result).toEqual('<div class="unknown-class group peer container p-0"></div>')
   })
+
+  test('parasite utilities', async ({ expect }) => {
+    let result = await format('<div class="group peer unknown-class p-0 container"></div>')
+
+    expect(result).toEqual('<div class="group peer unknown-class container p-0"></div>')
+  })
 })
 
 describe('whitespace', () => {
@@ -61,6 +67,6 @@ describe('whitespace', () => {
   test('duplicate classes are dropped', async ({ expect }) => {
     let result = await format('<div class="underline line-through underline flex"></div>')
 
-    expect(result).toEqual('<div class="flex underline line-through"></div>')
+    expect(result).toEqual('<div class="flex line-through underline"></div>')
   })
 })