feat: support for postcss 8 plugins

package.json

@@ -24,9 +24,9 @@
     "cssnano": "^4.0.0",
     "jest": "^24.0.0",
     "jsdoc-to-markdown": "^5.0.0",
-    "postcss": "^7.0.0",
+    "postcss": "^8.0.0",
     "postcss-import": "^12.0.0",
-    "postcss-nested": "^4.0.0",
+    "postcss-nested": "^5.0.0",
     "standard": "^12.0.0",
     "standard-version": "6.0.0",
     "sugarss": "^2.0.0"

src/plugins.js

@@ -64,11 +64,7 @@ const plugins = (config, file) => {
         plugin = plugin.default
       }
 
-      if (
-        // eslint-disable-next-line
-        !(typeof plugin === 'object' && Array.isArray(plugin.plugins) ||
-        typeof plugin === 'function')
-      ) {
+      if (!!plugin.plugins && Array.isArray(plugin.plugins)) {
         throw new TypeError(`Invalid PostCSS Plugin found at: plugins[${i}]\n\n(@${file})`)
       }
     })

test/js.test.js

@@ -4,6 +4,7 @@ const path = require('path')
 
 const postcss = require('postcss')
 const postcssrc = require('../src/index.js')
+const loadPlugins = require('../src/plugins.js')
 
 const { fixture, expected } = require('./utils.js')
 
@@ -35,7 +36,19 @@ describe('postcss.config.js - {Object} - Load Config', () => {
   test('Sync', () => {
     const config = postcssrc.sync(ctx, 'test/js/object')
 
-    expected(config)
+    expect(() => {
+      expected(config)
+    }).not.toThrowError()
+  })
+
+  test('Throw error if plugin has plugins too', () => {
+    expect(() => {
+      loadPlugins({
+        plugins: [{
+          plugins: ['postcssPlugin']
+        }]
+      }, undefined)
+    }).toThrowError()
   })
 })
 
@@ -85,7 +98,7 @@ describe('postcss.config.js - {Array} - Load Config', () => {
 
     expect(config.plugins.length).toEqual(2)
     expect(typeof config.plugins[0]).toBe('function')
-    expect(typeof config.plugins[1]).toBe('function')
+    expect(typeof config.plugins[1]).toBe('object')
 
     expect(config.file)
       .toEqual(path.resolve('test/js/array', 'postcss.config.js'))