feat(cli-service): support plugin to inject process-env before load config file

packages/@vue/cli-service/__tests__/Service.spec.js

@@ -247,6 +247,26 @@ test('api: defaultModes', () => {
   }
 
   createMockService([plugin2], false /* init */).run('test')
+
+  delete process.env.NODE_ENV
+  delete process.env.BABEL_ENV
+
+  const plugin3 = {
+    id: 'test-defaultModes',
+    apply: api => {
+      expect(process.env.NODE_ENV).toBe('test')
+      expect(process.env.BABEL_ENV).toBe('test')
+      expect(process.env.TEST_ENV).toBe('test-env')
+      api.registerCommand('bar', () => {})
+    }
+  }
+  plugin3.apply.defaultModes = {
+    bar: ['test', {
+      TEST_ENV: 'test-env'
+    }]
+  }
+
+  createMockService([plugin3], false /* init */).run('bar')
 })
 
 test('api: chainWebpack', () => {

packages/@vue/cli-service/lib/Service.js

@@ -1,6 +1,7 @@
 const fs = require('fs')
 const path = require('path')
 const debug = require('debug')
+const arrify = require('arrify')
 const { merge } = require('webpack-merge')
 const Config = require('webpack-chain')
 const PluginAPI = require('./PluginAPI')
@@ -39,7 +40,19 @@ module.exports = class Service {
     // this is provided by plugins as module.exports.defaultModes
     // so we can get the information without actually applying the plugin.
     this.modes = this.plugins.reduce((modes, { apply: { defaultModes } }) => {
-      return Object.assign(modes, defaultModes)
+      Object.keys(defaultModes || {}).forEach((cmd) => {
+        const [mode, extendEnv] = arrify(defaultModes[cmd])
+        Object.assign(modes, {
+          [cmd]: mode
+        })
+        // allow plugin to set addtional process.env
+        if (extendEnv) {
+          Object.keys(extendEnv).forEach((envKey) => {
+            process.env[envKey] = extendEnv[envKey]
+          })
+        }
+      })
+      return modes
     }, {})
   }
 

packages/@vue/cli-service/package.json

@@ -37,6 +37,7 @@
     "acorn": "^8.0.1",
     "acorn-walk": "^8.0.0",
     "address": "^1.1.2",
+    "arrify": "^2.0.1",
     "autoprefixer": "^10.1.0",
     "browserslist": "^4.16.0",
     "cache-loader": "^4.1.0",