Nice, mutating Vue app instances instead of global Vue instance is SO much better! 👍

Is there a reason for initializing app with the component? I'd see rather something like

import { createApp } from 'vue'
import App1 from './App1.vue';
import App2 from './App2.vue';

const app = createApp();
app.use(...);
...

app.mount('#app-1', App1);
app.mount('#app-2', App2);

That would allow to reuse the app object in some cases (but still you can create separate apps if you don't want to share anything)

@jacekkarczmarczyk

But conceptually shouldn't app contains only one "app"?

app.mount('#app-1', App1);
app.mount('#app-2', App2);

This seems rather counter intuitive. Perhaps it's the naming.

If you wish to use the same config in both apps, I reckon you can do something like:

import { createApp } from 'vue'
import App1 from './App1.vue';
import App2 from './App2.vue';

const createMyApp = (component) => {
  const app = createApp(component);

  app.config.ignoredElements = [/^app-/]
  app.use(/* ... */)
  app.mixin(/* ... */)
  app.component(/* ... */)
  app.directive(/* ... */)

  return app
};

createMyApp(App1).mount('#app-1');
createMyApp(App2).mount('#app-2');

In this case you gain more flexibility too over what config to use on each app.

Are the app methods chainable? It would be great if we could write:

import { createApp } from 'vue'
import App from './App.vue'

const app = createApp(App)

app.config.ignoredElements = [/^app-/]
app.use(/* ... */)
  .mixin(/* ... */)
  .component(/* ... */)
  .directive(/* ... */)
  .mount('#app')

And since I don't use the igoneElements feature, this could be simplified to:

import { createApp } from 'vue'
import App from './App.vue'

createApp(App)
  .use(/* ... */)
  .mixin(/* ... */)
  .component(/* ... */)
  .directive(/* ... */)
  .mount('#app')

@ycmjason I'm not sure whether an app should handle only one app, but that's also the point of discussion. But you're right that if it can handle more apps than the naming might be a subject to change

In this case you gain more flexibility too over what config to use on each app.

I don't agree with this, because my propsal allows you to use a separate apps/configs or shared one depending on your needs, your solution still doesn't allow to share the config.

Another question (not related to this topic) is where do we put Vuex or Router here?
app.mount('#app', { store }) or createApp(App, { store }) or we don't do it here at all?

For me it would make more sense to use:

createApp({ store, router })
  .use(/* ... */)
  .mixin(/* ... */)
  .component(/* ... */)
  .directive(/* ... */)
  .mount('#app', App)

This RFC is now in final comments stage. An RFC in final comments stage means that:

• The core team has reviewed the feedback and reached consensus about the general direction of the RFC and believe that this RFC is a worthwhile addition to the framework.
• Final comments stage does not mean the RFC's design details are final - we may still tweak the details as we implement it and discover new technical insights or constraints. It may even be further adjusted based on user feedback after it lands in an alpha/beta release.
• If no major objections with solid supporting arguments have been presented after a week, the RFC will be merged and become an active RFC.

Was thinking this will allow the devtools to inject a proper Vue app into the page instead of hand-made DOM manipulations (for the Component overlay for example).

I have some apps where there's no root component, is this sort of setup still possible with the new API? Couldn't figure out how to replicate this with the 3.0 alpha version.

import Vue from "vue";
import MyComponent from "@/MyComponent.vue";
import MyOtherComponent from "@/MyOtherComponent.vue";

Vue.component("my-component", MyComponent);
Vue.component("my-other-component", MyOtherComponent);

new Vue({
  el: "#app"
});

<div id="app">
  <div>
    <p>Some none-Vue stuff here.</p>
    <my-component foo="bar />
  </div>
  <my-other-component :foo="true" />
</div>

@lassemettovaara no, and I'd say don't do that. Importing a component should not have global side effects (registering global components). I misread your example. Yes, you should be able to simply mount an empty root component with no template:

import { createApp } from 'vue'

createApp().mount({}, '#app')

@lassemettovaara no, and I'd say don't do that. Importing a component should not have global side effects (registering global components). I misread your example. Yes, you should be able to simply mount an empty root component with no template:

import { createApp } from 'vue'

createApp().mount({}, '#app')

Thanks, that looks just like I expected it would work.

At the moment (in 3.0.0.-alpha.2) mounting an empty root component without a template just clears the host element on the page and throws a warning about a missing render function. Is this down to this just not being implemented yet, or does it look like a bug?

@lassemettovaara if you are using the webpack-based setup, then you are importing the runtime-only build by default, which does not support compiling DOM templates on the fly. I would suggest just migrate to use a root component so that you don't ship the compiler to the browser just for that.

The mentioned usage only works when you are using the full build.

这种设计非常棒，从设计上支持了多实例，方便前端做模块隔离，一个应用是一个沙盒，对大项目微服务化有了很好的支持，避免巨石的产生。

建议，从接口层面，增加实例间的互动，如通讯、状态共享等特性；从构建层面支持多实例的代码复用，包共享等。

This design is very good. It supports multiple instances from the design, which is convenient for the front-end to do module isolation. An application is a sandbox, which has a good support for micro service of large projects and avoids the generation of boulders.

It is suggested to increase the interaction between instances from the interface level, such as communication, state sharing and other features; support multi instance code reuse, package sharing and so on from the webpack level.