132 lines
3.6 KiB
Markdown
132 lines
3.6 KiB
Markdown
---
|
|
stage: none
|
|
group: unassigned
|
|
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
|
|
---
|
|
|
|
# Migration to Vue 3
|
|
|
|
In order to prepare for the eventual migration to Vue 3.x, we should be wary about adding the following features to the codebase:
|
|
|
|
## Vue filters
|
|
|
|
**Why?**
|
|
|
|
Filters [are removed](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0015-remove-filters.md) from the Vue 3 API completely.
|
|
|
|
**What to use instead**
|
|
|
|
Component's computed properties / methods or external helpers.
|
|
|
|
## Event hub
|
|
|
|
**Why?**
|
|
|
|
`$on`, `$once`, and `$off` methods [are removed](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0020-events-api-change.md) from the Vue instance, so in Vue 3 it can't be used to create an event hub.
|
|
|
|
**What to use instead**
|
|
|
|
Vue documentation recommends using the [mitt](https://github.com/developit/mitt) library. It's relatively small (200 bytes gzipped) and has a clear API:
|
|
|
|
```javascript
|
|
import mitt from 'mitt'
|
|
|
|
const emitter = mitt()
|
|
|
|
// listen to an event
|
|
emitter.on('foo', e => console.log('foo', e) )
|
|
|
|
// listen to all events
|
|
emitter.on('*', (type, e) => console.log(type, e) )
|
|
|
|
// fire an event
|
|
emitter.emit('foo', { a: 'b' })
|
|
|
|
// working with handler references:
|
|
function onFoo() {}
|
|
|
|
emitter.on('foo', onFoo) // listen
|
|
emitter.off('foo', onFoo) // unlisten
|
|
```
|
|
|
|
**Event hub factory**
|
|
|
|
We have created a factory that you can use to instantiate a new mitt-based event hub.
|
|
This makes it easier to migrate existing event hubs to the new recommended approach, or
|
|
to create new ones.
|
|
|
|
```javascript
|
|
import createEventHub from '~/helpers/event_hub_factory';
|
|
|
|
export default createEventHub();
|
|
```
|
|
|
|
Event hubs created with the factory expose the same methods as Vue 2 event hubs (`$on`, `$once`, `$off` and
|
|
`$emit`), making them backward compatible with our previous approach.
|
|
|
|
## \<template functional>
|
|
|
|
**Why?**
|
|
|
|
In Vue 3, `{ functional: true }` option [is removed](https://github.com/vuejs/rfcs/blob/functional-async-api-change/active-rfcs/0007-functional-async-api-change.md) and `<template functional>` is no longer supported.
|
|
|
|
**What to use instead**
|
|
|
|
Functional components must be written as plain functions:
|
|
|
|
```javascript
|
|
import { h } from 'vue'
|
|
|
|
const FunctionalComp = (props, slots) => {
|
|
return h('div', `Hello! ${props.name}`)
|
|
}
|
|
```
|
|
|
|
It is not recommended to replace stateful components with functional components unless you absolutely need a performance improvement right now. In Vue 3, performance gains for functional components are negligible.
|
|
|
|
## Old slots syntax with `slot` attribute
|
|
|
|
**Why?**
|
|
|
|
In Vue 2.6 `slot` attribute was already deprecated in favor of `v-slot` directive. The `slot` attribute usage is still allowed and sometimes we prefer using it because it simplifies unit tests (with old syntax, slots are rendered on `shallowMount`). However, in Vue 3 we can't use old syntax anymore.
|
|
|
|
**What to use instead**
|
|
|
|
The syntax with `v-slot` directive. To fix rendering slots in `shallowMount`, we need to stub a child component with slots explicitly.
|
|
|
|
```html
|
|
<!-- MyAwesomeComponent.vue -->
|
|
<script>
|
|
import SomeChildComponent from './some_child_component.vue'
|
|
|
|
export default {
|
|
components: {
|
|
SomeChildComponent
|
|
}
|
|
}
|
|
|
|
</script>
|
|
|
|
<template>
|
|
<div>
|
|
<h1>Hello GitLab!</h1>
|
|
<some-child-component>
|
|
<template #header>
|
|
Header content
|
|
</template>
|
|
</some-child-component>
|
|
</div>
|
|
</template>
|
|
```
|
|
|
|
```javascript
|
|
// MyAwesomeComponent.spec.js
|
|
|
|
import SomeChildComponent from '~/some_child_component.vue'
|
|
|
|
shallowMount(MyAwesomeComponent, {
|
|
stubs: {
|
|
SomeChildComponent
|
|
}
|
|
})
|
|
```
|