initDev() Not being called in the browser

[d-pollard]

Version

3.0.0-rc.5

Reproduction link

https://github.com/d-pollard/testing-vue3

Steps to reproduce

Vue CLI generate a new app;
npm run serve

open dev tools; see that window.__VUE__ isn't set

What is expected?

initDev() should run (setting __VUE__ and running setDevtoolsHook with __VUE_DEVTOOLS_GLOBAL_HOOK__)

What is actually happening?

These fields aren't being set; initDev is being called when we build instead

---

I can add import 'vue/dist/vue.esm-bundler'; in main.js and it'll set properly

[d-pollard]

@sodatea - would love to contribute a PR for this; as it stands a fix as I see it would be something like this:

User based approach

vue.config.js

module.exports = {
  runtimeCompiler: process.env.NODE_ENV === 'development'
};

CLI source fix

The alternative would be to check the environment we're running in here: https://github.com/vuejs/vue-cli/blob/dev/packages/%40vue/cli-service/lib/config/base.js#L118

webpackConfig.resolve
        .alias
          .set(
            'vue$',
            options.runtimeCompiler || process.env.NODE_ENV === 'development'
              ? 'vue/dist/vue.esm-bundler.js'
              : '@vue/runtime-dom'
          )

Please advise which approach you'd prefer; alternatively, suggest a fix and I'll implement it

[haoqunjiang]

@d-pollard See #5788