fix: monkey-patch Vite HMR issue & make it reproducible (#464)

package.json

@@ -27,26 +27,27 @@
   "dependencies": {
     "@nuxt/kit": "^3.0.0-rc.4",
     "@nuxt/postcss8": "^1.1.3",
-    "@types/tailwindcss": "^3.0.10",
+    "@types/tailwindcss": "^3.0.11",
     "autoprefixer": "^10.4.7",
     "chalk": "^5.0.1",
     "clear-module": "^4.1.2",
     "consola": "^2.15.3",
     "defu": "^6.0.0",
     "postcss": "^8.4.14",
     "postcss-custom-properties": "^12.1.8",
-    "postcss-nesting": "^10.1.8",
+    "postcss-nesting": "^10.1.10",
     "tailwind-config-viewer": "^1.7.1",
-    "tailwindcss": "^3.1.4",
-    "ufo": "^0.8.4"
+    "tailwindcss": "^3.1.5",
+    "ufo": "^0.8.5"
   },
   "devDependencies": {
+    "@fontsource/inter": "^4.5.11",
     "@nuxt/module-builder": "latest",
     "@nuxt/test-utils": "latest",
     "@nuxtjs/eslint-config-typescript": "latest",
     "codecov": "latest",
     "eslint": "latest",
-    "nuxt": "^3.0.0-rc.4",
+    "nuxt": "npm:nuxt3@latest",
     "standard-version": "latest"
   }
 }

playground/nuxt.config.ts

@@ -7,5 +7,13 @@ export default defineNuxtConfig({
   ],
   tailwindcss: {
     exposeConfig: true
-  }
+  },
+  css: [
+    // Including Inter CSS is the first component to reproduce HMR issue. It also causes playground to look better,
+    // since Inter is a native font for Tailwind UI
+    '@fontsource/inter/400.css',
+    '@fontsource/inter/500.css',
+    '@fontsource/inter/600.css',
+    '@fontsource/inter/700.css'
+  ]
 })

playground/pages/index.vue

@@ -0,0 +1,25 @@
+<template>
+  <div>
+    <div>
+      <CallToAction />
+    </div>
+    <div class="max-w-screen-lg p-4 mx-auto space-y-4">
+      <div>
+        <span class="pr-1 font-medium">This is a HMR test, try changing the color:</span>
+        <span class="text-indigo-500">meow!</span>
+      </div>
+      <div>
+        <span class="text-sm font-semibold text-gray-700">Resolved tailwind config:</span>
+        <textarea
+          class="p-4 block text-sm border border-gray-100 rounded shadow w-full h-[32rem] font-mono outline-none"
+          readonly
+          :value="JSON.stringify(tailwindConfig, null, 2)"
+        />
+      </div>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import tailwindConfig from '#tailwind-config'
+</script>

playground/tailwind.config.js

@@ -0,0 +1,9 @@
+export default {
+  theme: {
+    extend: {
+      fontFamily: {
+        sans: 'Inter, ui-sans-serif, system-ui, -apple-system, Arial, Roboto, sans-serif'
+      }
+    }
+  }
+}

src/hmr.ts

@@ -0,0 +1,40 @@
+import { isAbsolute, resolve } from 'path'
+import { HmrContext, Plugin } from 'vite'
+import minimatch from 'minimatch'
+
+export default function (tailwindConfig, rootDir: string, cssPath: string): Plugin {
+  const resolvedContent: string[] = tailwindConfig.content.map(f => !isAbsolute(f) ? resolve(rootDir, f) : f)
+
+  return {
+    name: 'nuxt:tailwindcss',
+    handleHotUpdate (ctx: HmrContext): void {
+      if (resolvedContent.findIndex(c => minimatch(ctx.file, c)) === -1) {
+        return
+      }
+
+      const extraModules = ctx.server.moduleGraph.getModulesByFile(cssPath)
+      const timestamp = +Date.now()
+
+      for (const mod of extraModules) {
+        // This will invalidate Vite cache (e.g. next page reload will be fine), but won't help with HMR on its own
+        ctx.server.moduleGraph.invalidateModule(mod, undefined, timestamp)
+      }
+
+      // Surely, this is not the best way to fix that, especially given direct `send` call bypassing all Vite logic.
+      // But just returning extra modules does not cause Vite to send the update, and I didn't find a way to trigger
+      // that update manually other than sending it directly
+
+      ctx.server.ws.send({
+        type: 'update',
+        updates: Array.from(extraModules).map((mod) => {
+          return {
+            type: mod.type === 'js' ? 'js-update' : 'css-update',
+            path: mod.url,
+            acceptedPath: mod.url,
+            timestamp
+          }
+        })
+      })
+    }
+  }
+};

src/module.ts

@@ -11,9 +11,11 @@ import {
   requireModule,
   isNuxt2,
   createResolver,
-  resolvePath
+  resolvePath,
+  addVitePlugin
 } from '@nuxt/kit'
 import { name, version } from '../package.json'
+import vitePlugin from './hmr'
 import defaultTailwindConfig from './tailwind.config'
 
 const logger = consola.withScope('nuxt:tailwindcss')
@@ -34,25 +36,32 @@ export default defineNuxtModule({
     config: defaultTailwindConfig(nuxt.options),
     viewer: true,
     exposeConfig: false,
-    injectPosition: 0
+    injectPosition: 0,
+    disableHmrHotfix: false
   }),
   async setup (moduleOptions, nuxt) {
     const configPath = await resolvePath(moduleOptions.configPath)
     const cssPath = await resolvePath(moduleOptions.cssPath, { extensions: ['.css', '.sass', '.scss', '.less', '.styl'] })
     const injectPosition = ~~Math.min(moduleOptions.injectPosition, (nuxt.options.css || []).length + 1)
 
     // Include CSS file in project css
+    let resolvedCss: string
     if (typeof cssPath === 'string') {
       if (existsSync(cssPath)) {
         logger.info(`Using Tailwind CSS from ~/${relative(nuxt.options.srcDir, cssPath)}`)
-        nuxt.options.css.splice(injectPosition, 0, cssPath)
+        resolvedCss = cssPath
       } else {
         logger.info('Using default Tailwind CSS file from runtime/tailwind.css')
-        const resolver = createResolver(import.meta.url)
-        nuxt.options.css.splice(injectPosition, 0, resolver.resolve('runtime/tailwind.css'))
+        resolvedCss = createResolver(import.meta.url).resolve('runtime/tailwind.css')
       }
     }
 
+    // Inject only if this file isn't listed already by user (e.g. user may put custom path both here and in css):
+    const resolvedNuxtCss = await Promise.all(nuxt.options.css.map(p => resolvePath(p)))
+    if (!resolvedNuxtCss.includes(resolvedCss)) {
+      nuxt.options.css.splice(injectPosition, 0, resolvedCss)
+    }
+
     // Extend the Tailwind config
     let tailwindConfig: any = {}
     if (existsSync(configPath)) {
@@ -111,6 +120,11 @@ export default defineNuxtModule({
       await installModule('@nuxt/postcss8')
     }
 
+    if (nuxt.options.dev && !moduleOptions.disableHmrHotfix) {
+      // Insert Vite plugin to work around HMR issue
+      addVitePlugin(vitePlugin(tailwindConfig, nuxt.options.rootDir, resolvedCss))
+    }
+
     // Add _tailwind config viewer endpoint
     if (nuxt.options.dev && moduleOptions.viewer) {
       const route = '/_tailwind'