Add mechanism to return registered plugins from CSS

packages/tailwindcss/src/index.ts

@@ -11,8 +11,10 @@ export function compile(
   config?: UserConfig,
 ): {
   build(candidates: string[]): string
+  readonly plugins: string[]
 } {
   let resolved = resolve(config ?? {})
+  let plugins: string[] = []
 
   let ast = CSS.parse(css)
 
@@ -53,6 +55,20 @@ export function compile(
       replaceWith(node.nodes)
     }
 
+    if (node.selector.startsWith('@plugin')) {
+      let path = node.selector
+        // Ignore `@plugin` when parsing the selector
+        .slice(7)
+        // Remove any surrounding spaces
+        .trim()
+        // Remove the surrounding quotes
+        .slice(1, -1)
+
+      plugins.push(path)
+      replaceWith([])
+      return WalkAction.Skip
+    }
+
     if (node.selector !== '@theme' && node.selector !== '@theme reference') return
 
     let isReference = node.selector === '@theme reference'
@@ -194,6 +210,7 @@ export function compile(
   let previousAstNodeCount = 0
 
   return {
+    plugins,
     build(newRawCandidates: string[]) {
       let didChange = false
 
@@ -254,5 +271,5 @@ export function __unstable__loadDesignSystem(css: string) {
     })
   })
 
-  return buildDesignSystem(theme)
+  return buildDesignSystem(theme, resolve({}))
 }

packages/tailwindcss/src/plugins.test.ts

@@ -1,7 +1,10 @@
 import { test, vi } from 'vitest'
+import { compile } from '.'
 import type { UserConfig } from './config'
 import { run } from './test-utils/run'
 
+const css = String.raw
+
 test('Plugins are called', ({ expect }) => {
   let fn = vi.fn()
   let handler = vi.fn()
@@ -140,3 +143,12 @@ test('Custom functional variants', ({ expect }) => {
   `)
   expect(run(['in-[:checked]/foo:underline'], config)).toEqual('')
 })
+
+test('Plugins registered in CSS can be returned', ({ expect }) => {
+  let builder = compile(css`
+    @plugin "my-plugin";
+    @plugin "./my-plugin";
+  `)
+
+  expect(builder.plugins).toEqual(['my-plugin', './my-plugin'])
+})