Add support for the tailwindcss/plugin export (#14173)

This PR adds support for the `tailwindcss/plugin` import which has
historically been used to define custom plugins:

```js
import plugin from "tailwindcss/plugin";

export default plugin(function ({ addBase }) {
  addBase({
    // ...
  });
});
```

This also adds support for `plugin.withOptions` which was used to define
plugins that took optional initilization options when they were
registered in your `tailwind.config.js` file:

```js
import plugin from "tailwindcss/plugin";

export default plugin.withOptions((options = {}) => {
  return function ({ addBase }) {
    addBase({
      // ...
    });
  };
});
```

We've stubbed out support for the `config` argument but we're not
actually doing anything with it at the time of this PR. The scope of
this PR is just to allow people to create plugins that currently work
using the raw function syntax but using the `plugin` and
`plugin.withOptions` APIs. Support for `config` will land separately.

---------

Co-authored-by: Adam Wathan <[email protected]>

Author: thecrypticace

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Add support for `addBase` plugins using the `@plugin` directive ([#14172](https://github.com/tailwindlabs/tailwindcss/pull/14172))
+- Add support for the `tailwindcss/plugin` export ([#14173](https://github.com/tailwindlabs/tailwindcss/pull/14173))
 
 ## [4.0.0-alpha.19] - 2024-08-09
 

packages/tailwindcss/package.json

@@ -23,6 +23,10 @@
       "require": "./dist/lib.js",
       "import": "./src/index.ts"
     },
+    "./plugin": {
+      "require": "./src/plugin.cts",
+      "import": "./src/plugin.ts"
+    },
     "./package.json": "./package.json",
     "./index.css": "./index.css",
     "./index": "./index.css",
@@ -43,6 +47,10 @@
         "require": "./dist/lib.js",
         "import": "./dist/lib.mjs"
       },
+      "./plugin": {
+        "require": "./dist/plugin.js",
+        "import": "./src/plugin.mjs"
+      },
       "./package.json": "./package.json",
       "./index.css": "./index.css",
       "./index": "./index.css",

packages/tailwindcss/src/index.test.ts

@@ -2,6 +2,7 @@ import fs from 'node:fs'
 import path from 'node:path'
 import { describe, expect, it, test } from 'vitest'
 import { compile } from '.'
+import type { PluginAPI } from './plugin-api'
 import { compileCss, optimizeCss, run } from './test-utils/run'
 
 const css = String.raw
@@ -1299,7 +1300,7 @@ describe('plugins', () => {
         `,
         {
           loadPlugin: async () => {
-            return ({ addVariant }) => {
+            return ({ addVariant }: PluginAPI) => {
               addVariant('hocus', '&:hover, &:focus')
             }
           },
@@ -1317,7 +1318,7 @@ describe('plugins', () => {
         `,
         {
           loadPlugin: async () => {
-            return ({ addVariant }) => {
+            return ({ addVariant }: PluginAPI) => {
               addVariant('hocus', '&:hover, &:focus')
             }
           },
@@ -1335,7 +1336,7 @@ describe('plugins', () => {
       `,
       {
         loadPlugin: async () => {
-          return ({ addVariant }) => {
+          return ({ addVariant }: PluginAPI) => {
             addVariant('hocus', '&:hover, &:focus')
           }
         },
@@ -1366,7 +1367,7 @@ describe('plugins', () => {
       `,
       {
         loadPlugin: async () => {
-          return ({ addVariant }) => {
+          return ({ addVariant }: PluginAPI) => {
             addVariant('hocus', ['&:hover', '&:focus'])
           }
         },
@@ -1398,7 +1399,7 @@ describe('plugins', () => {
       `,
       {
         loadPlugin: async () => {
-          return ({ addVariant }) => {
+          return ({ addVariant }: PluginAPI) => {
             addVariant('hocus', {
               '&:hover': '@slot',
               '&:focus': '@slot',
@@ -1432,7 +1433,7 @@ describe('plugins', () => {
       `,
       {
         loadPlugin: async () => {
-          return ({ addVariant }) => {
+          return ({ addVariant }: PluginAPI) => {
             addVariant('hocus', {
               '@media (hover: hover)': {
                 '&:hover': '@slot',
@@ -1480,7 +1481,7 @@ describe('plugins', () => {
       `,
       {
         loadPlugin: async () => {
-          return ({ addVariant }) => {
+          return ({ addVariant }: PluginAPI) => {
             addVariant('hocus', {
               '&': {
                 '--custom-property': '@slot',
@@ -1518,7 +1519,7 @@ describe('plugins', () => {
 
       {
         loadPlugin: async () => {
-          return ({ addVariant }) => {
+          return ({ addVariant }: PluginAPI) => {
             addVariant('dark', '&:is([data-theme=dark] *)')
           }
         },
@@ -2087,7 +2088,7 @@ test('addBase', async () => {
 
     {
       loadPlugin: async () => {
-        return ({ addBase }) => {
+        return ({ addBase }: PluginAPI) => {
           addBase({
             body: {
               'font-feature-settings': '"tnum"',

packages/tailwindcss/src/index.ts

@@ -4,14 +4,12 @@ import { WalkAction, comment, decl, rule, toCss, walk, type Rule } from './ast'
 import { compileCandidates } from './compile'
 import * as CSS from './css-parser'
 import { buildDesignSystem, type DesignSystem } from './design-system'
-import { buildPluginApi, type PluginAPI } from './plugin-api'
+import { registerPlugins, type Plugin } from './plugin-api'
 import { Theme } from './theme'
 import { segment } from './utils/segment'
 
 const IS_VALID_UTILITY_NAME = /^[a-z][a-zA-Z0-9/%._-]*$/
 
-type Plugin = (api: PluginAPI) => void
-
 type CompileOptions = {
   loadPlugin?: (path: string) => Promise<Plugin>
 }
@@ -40,7 +38,7 @@ async function parseCss(css: string, { loadPlugin = throwOnPlugin }: CompileOpti
 
   // Find all `@theme` declarations
   let theme = new Theme()
-  let pluginLoaders: Promise<Plugin>[] = []
+  let pluginPaths: string[] = []
   let customVariants: ((designSystem: DesignSystem) => void)[] = []
   let customUtilities: ((designSystem: DesignSystem) => void)[] = []
   let firstThemeRule: Rule | null = null
@@ -60,7 +58,7 @@ async function parseCss(css: string, { loadPlugin = throwOnPlugin }: CompileOpti
         throw new Error('`@plugin` cannot be nested.')
       }
 
-      pluginLoaders.push(loadPlugin(node.selector.slice(9, -1)))
+      pluginPaths.push(node.selector.slice(9, -1))
       replaceWith([])
       return
     }
@@ -281,9 +279,9 @@ async function parseCss(css: string, { loadPlugin = throwOnPlugin }: CompileOpti
     customUtility(designSystem)
   }
 
-  let pluginApi = buildPluginApi(designSystem, ast)
+  let plugins = await Promise.all(pluginPaths.map(loadPlugin))
 
-  await Promise.all(pluginLoaders.map((loader) => loader.then((plugin) => plugin(pluginApi))))
+  registerPlugins(plugins, designSystem, ast)
 
   // Replace `@apply` rules with the actual utility classes.
   if (css.includes('@apply')) {

packages/tailwindcss/src/plugin-api.ts

@@ -4,6 +4,17 @@ import type { DesignSystem } from './design-system'
 import { withAlpha, withNegative } from './utilities'
 import { inferDataType } from './utils/infer-data-type'
 
+export type Config = Record<string, any>
+
+export type PluginFn = (api: PluginAPI) => void
+export type PluginWithConfig = { handler: PluginFn; config?: Partial<Config> }
+export type PluginWithOptions<T> = {
+  (options?: T): PluginWithConfig
+  __isOptionsFunction: true
+}
+
+export type Plugin = PluginFn | PluginWithConfig | PluginWithOptions<any>
+
 export type PluginAPI = {
   addBase(base: CssInJs): void
   addVariant(name: string, variant: string | string[] | CssInJs): void
@@ -177,3 +188,25 @@ export function buildPluginApi(designSystem: DesignSystem, ast: AstNode[]): Plug
     },
   }
 }
+
+export function registerPlugins(plugins: Plugin[], designSystem: DesignSystem, ast: AstNode[]) {
+  let pluginApi = buildPluginApi(designSystem, ast)
+
+  for (let plugin of plugins) {
+    if ('__isOptionsFunction' in plugin) {
+      // Happens with `plugin.withOptions()` when no options were passed:
+      // e.g. `require("my-plugin")` instead of `require("my-plugin")(options)`
+      plugin().handler(pluginApi)
+    } else if ('handler' in plugin) {
+      // Happens with `plugin(…)`:
+      // e.g. `require("my-plugin")`
+      //
+      // or with `plugin.withOptions()` when the user passed options:
+      // e.g. `require("my-plugin")(options)`
+      plugin.handler(pluginApi)
+    } else {
+      // Just a plain function without using the plugin(…) API
+      plugin(pluginApi)
+    }
+  }
+}

packages/tailwindcss/src/plugin.cts

@@ -0,0 +1,5 @@
+// This file exists so that `plugin.ts` can be written one time but be compatible with both CJS and
+// ESM. Without it we get a `.default` export when using `require` in CJS.
+
+// @ts-ignore
+module.exports = require('./plugin.ts').default

packages/tailwindcss/src/plugin.test.ts

@@ -0,0 +1,61 @@
+import { test } from 'vitest'
+import { compile } from '.'
+import plugin from './plugin'
+
+const css = String.raw
+
+test('plugin', async ({ expect }) => {
+  let input = css`
+    @plugin "my-plugin";
+  `
+
+  let compiler = await compile(input, {
+    loadPlugin: async () => {
+      return plugin(function ({ addBase }) {
+        addBase({
+          body: {
+            margin: '0',
+          },
+        })
+      })
+    },
+  })
+
+  expect(compiler.build([])).toMatchInlineSnapshot(`
+    "@layer base {
+      body {
+        margin: 0;
+      }
+    }
+    "
+  `)
+})
+
+test('plugin.withOptions', async ({ expect }) => {
+  let input = css`
+    @plugin "my-plugin";
+  `
+
+  let compiler = await compile(input, {
+    loadPlugin: async () => {
+      return plugin.withOptions(function (opts = { foo: '1px' }) {
+        return function ({ addBase }) {
+          addBase({
+            body: {
+              margin: opts.foo,
+            },
+          })
+        }
+      })
+    },
+  })
+
+  expect(compiler.build([])).toMatchInlineSnapshot(`
+    "@layer base {
+      body {
+        margin: 1px;
+      }
+    }
+    "
+  `)
+})

packages/tailwindcss/src/plugin.ts

@@ -0,0 +1,26 @@
+import type { Config, PluginFn, PluginWithConfig, PluginWithOptions } from './plugin-api'
+
+function createPlugin(handler: PluginFn, config?: Partial<Config>): PluginWithConfig {
+  return {
+    handler,
+    config,
+  }
+}
+
+createPlugin.withOptions = function <T>(
+  pluginFunction: (options?: T) => PluginFn,
+  configFunction: (options?: T) => Partial<Config> = () => ({}),
+): PluginWithOptions<T> {
+  function optionsFunction(options: T): PluginWithConfig {
+    return {
+      handler: pluginFunction(options),
+      config: configFunction(options),
+    }
+  }
+
+  optionsFunction.__isOptionsFunction = true as const
+
+  return optionsFunction as PluginWithOptions<T>
+}
+
+export default createPlugin