Destructured env vars not replaced in --modern builds

[runarberg]

Version

4.0.0-rc.7

Reproduction link

https://github.com/runarberg/vue-cli-modern-process-env-fail

Environment info

$ npx @vue/cli@next info

Environment Info:

  System:
    OS: Linux 5.0 Ubuntu 19.04 (Disco Dingo)
    CPU: (4) x64 Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz
  Binaries:
    Node: 12.11.1 - ~/.nvm/versions/node/v12.11.1/bin/node
    Yarn: Not Found
    npm: 6.11.3 - ~/.nvm/versions/node/v12.11.1/bin/npm
  Browsers:
    Chrome: Not Found
    Firefox: 69.0
  npmPackages:
    @vue/babel-helper-vue-jsx-merge-props:  1.0.0 
    @vue/babel-plugin-transform-vue-jsx:  1.0.0 
    @vue/babel-preset-app:  4.0.0-rc.7 
    @vue/babel-preset-jsx:  1.1.0 
    @vue/babel-sugar-functional-vue:  1.0.0 
    @vue/babel-sugar-inject-h:  1.0.0 
    @vue/babel-sugar-v-model:  1.0.0 
    @vue/babel-sugar-v-on:  1.1.0 
    @vue/cli-overlay:  4.0.0-rc.7 
    @vue/cli-plugin-babel: ^4.0.0-rc.7 => 4.0.0-rc.7 
    @vue/cli-plugin-eslint: ^4.0.0-rc.7 => 4.0.0-rc.7 
    @vue/cli-service: ^4.0.0-rc.7 => 4.0.0-rc.7 
    @vue/cli-shared-utils:  4.0.0-rc.7 
    @vue/component-compiler-utils:  3.0.0 
    @vue/preload-webpack-plugin:  1.1.1 
    @vue/web-component-wrapper:  1.2.0 
    eslint-plugin-vue: ^5.0.0 => 5.2.3 
    vue: ^2.6.10 => 2.6.10 
    vue-eslint-parser:  5.0.0 
    vue-hot-reload-api:  2.3.4 
    vue-loader:  15.7.1 
    vue-style-loader:  4.1.2 
    vue-template-compiler: ^2.6.10 => 2.6.10 
    vue-template-es2015-compiler:  1.9.1 
  npmGlobalPackages:
    @vue/cli: Not Found

Steps to reproduce

Destructure process.env somewhere in your code:

<template>
  <HelloWorld :msg="msg" />
</template>

<script>
const { VUE_APP_MSG: msg } = process.env;

export default {
  data() {
    return {
      msg,
    };
  },
};
</script>

Add the env var to your .env:

 VUE_APP_MSG="Hello, Bug!"

Then build with the --modern flag:

npm run build -- --modern

What is expected?

The build output should have the destructured env vars replaced. That is msg should be set to "Hello, Bug!".

What is actually happening?

This only happens in the legacy build. In the modern build the variable is undefined.

---

I think this is a regression. I think this worked as expected in vue-cli 3.

[haoqunjiang]

Caused by #3782. See the reasoning at #3579
I'm wondering if we can revert it though. I need to test it out locally.