update to @nuxt/postcss8

lib/module.js

@@ -21,8 +21,18 @@ module.exports = async function (moduleOptions) {
   const configPath = nuxt.resolver.resolveAlias(options.configPath)
   const cssPath = nuxt.resolver.resolveAlias(options.cssPath)
 
+  // Extend postcss config
+  // https://tailwindcss.com/docs/using-with-preprocessors#future-css-features
+  nuxt.options.build.postcss = defu(nuxt.options.build.postcss, {
+    plugins: {
+      tailwindcss: {},
+      'postcss-nested': {},
+      'postcss-custom-properties': {}
+    }
+  })
+
   // Require postcss@8
-  await this.addModule('nuxt-postcss8')
+  await this.addModule('@nuxt/postcss8')
 
   // Include CSS file in project css
   if (await pathExists(cssPath)) {
@@ -58,29 +68,10 @@ module.exports = async function (moduleOptions) {
     if (!nuxt.options.dev && !process.env.NODE_ENV) {
       process.env.NODE_ENV = 'production'
     }
-    /*
-    ** Set PostCSS config
-    */
-    const { postcss } = nuxt.options.build
-    postcss.plugins = postcss.plugins || {}
 
-    // No working at the moment: https://github.com/csstools/postcss-preset-env/issues/191
-    // postcss.preset.stage = 1 // see https://tailwindcss.com/docs/using-with-preprocessors#future-css-features
-    // Let's use postcss-nested
-    postcss.plugins['postcss-nested'] = postcss.plugins['postcss-nested'] || {}
-
-    // Let modules extend the tailwind config
+    // Set tailwindcss config
     await nuxt.callHook('tailwindcss:config', tailwindConfig)
-
-    /* istanbul ignore if */
-    if (Array.isArray(postcss.plugins)) {
-      logger.error('Array syntax for postcss plugins is not supported with v3. Please use the object syntax: https://nuxtjs.org/guides/configuration-glossary/configuration-build#postcss')
-    } else if (typeof postcss.plugins === 'object') {
-      postcss.plugins.tailwindcss = tailwindConfig
-    }
-
-    // Add postcss autoprefixer plugin
-    postcss.plugins.autoprefixer = postcss.plugins.autoprefixer || {}
+    nuxt.options.build.postcss.plugins.tailwindcss = tailwindConfig
 
     /*
     ** Expose resolved tailwind config as an alias

package.json

@@ -31,7 +31,7 @@
     "consola": "^2.15.3",
     "defu": "^3.2.2",
     "fs-extra": "^9.1.0",
-    "nuxt-postcss8": "^1.1.1",
+    "@nuxt/postcss8": "^1.1.3",
     "postcss": "^8.2.7",
     "postcss-nested": "^5.0.5",
     "tailwind-config-viewer": "^1.5.0",
@@ -58,7 +58,7 @@
     "eslint-plugin-vue": "^7.7.0",
     "husky": "^5.1.3",
     "jest": "^26.6.3",
-    "nuxt": "^2.15.2",
+    "nuxt": "^2.15.3",
     "standard-version": "^9.1.1"
   }
 }