@vue/reactivity-transform

> ⚠️ This is experimental and the proposal has been dropped.
> The feature is now marked as deprecated and will be removed from Vue core
> in 3.4.
>
> See reason for deprecation here.

Basic Rules

- Ref-creating APIs have $-prefixed versions that create reactive variables instead. They also do not need to be explicitly imported. These include:
- ref
- computed
- shallowRef
- customRef
- toRef
- $() can be used to destructure an object into reactive variables, or turn existing refs into reactive variables
- $$() to "escape" the transform, which allows access to underlying refs

``js
import { watchEffect } from 'vue'

// bind ref as a variable
let count = $ref(0)

watchEffect(() => {
// no need for .value
console.log(count)
})

// assignments are reactive
count++

// get the actual ref
console.log($$(count)) // { value: 1 }
`

Macros can be optionally imported to make it more explicit:

`js
// not necessary, but also works
import { $, $ref } from 'vue/macros'

let count = $ref(0)
const { x, y } = $(useMouse())
`

$3

To enable types for the macros globally, include the following in a .d.ts file:

`ts
///
`

API

This package is the lower-level transform that can be used standalone. Higher-level tooling (e.g. @vitejs/plugin-vue and vue-loader) will provide integration via options.

$3

Can be used to do a cheap check to determine whether full transform should be performed.

`js
import { shouldTransform } from '@vue/reactivity-transform'

shouldTransform(let a = ref(0)) // false
shouldTransform(let a = $ref(0)) // true
`

$3

`js
import { transform } from '@vue/reactivity-transform'

const src = let a = $ref(0); a++
const {
code, // import { ref as _ref } from 'vue'; let a = (ref(0)); a.value++"
map
} = transform(src, {
filename: 'foo.ts',
sourceMap: true,

// @babel/parser plugins to enable.
// 'typescript' and 'jsx' will be auto-inferred from filename if provided,
// so in most cases explicit parserPlugins are not necessary
parserPlugins: [
/ ... /
]
})
`

Options

`ts
interface RefTransformOptions {
filename?: string
sourceMap?: boolean // default: false
parserPlugins?: ParserPlugin[]
importHelpersFrom?: string // default: "vue"
}
`

$3

Transform with an existing Babel AST + MagicString instance. This is used internally by @vue/compiler-sfc to avoid double parse/transform cost.

`js
import { transformAST } from '@vue/reactivity-transform'
import { parse } from '@babel/parser'
import MagicString from 'magic-string'

const src = let a = $ref(0); a++
const ast = parse(src, { sourceType: 'module' })
const s = new MagicString(src)

const {
rootRefs, // ['a']
importedHelpers // ['ref']
} = transformAST(ast, s)

console.log(s.toString()) // let a = _ref(0); a.value++
``