-[x] Basic testing setup and a dummy CLI

-[x] Support applying`jscodeshift` codemods to`.vue` files

-[x] Provide a programmatic interface for usage in`vue-cli-plugin-vue-next`

-[ ] (WIP) Set up tests

-[x] Set up tests

-[ ] (WIP) Implement the transformations described below for migration usage

-[ ] Built-in transformations need to support TypeScript

-[ ] Built-in transformations need to support module systems other than ES module, and those without modules

5. Make sure to use the compat build of vue@3

6. Serve the app in development mode, fix the runtime deprecation warnings

Legend of annotations:

| Mark| Description|

| ----| ----------------------------------------------------|

| 🔴| work not started|

| 🟠| on-going work|

| 🟢| implemented (may have uncovered edge cases)|

| 🔵| needs to or can be implemented in the compat runtime|

-🟢[RFC05: Replace`v-bind`'s`.sync` with a`v-model` argument](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0005-replace-v-bind-sync-with-v-model-argument.md)

-[RFC05: Replace`v-bind`'s`.sync` with a`v-model` argument](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0005-replace-v-bind-sync-with-v-model-argument.md)

- Can be detected and fixed by the[`vue/no-deprecated-v-bind-sync`](https://eslint.vuejs.org/rules/no-deprecated-v-bind-sync.html) ESLint rule

-🟢[RFC14: Remove`keyCode` support in`v-on`](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0014-drop-keycode-support.md)

-[RFC14: Remove`keyCode` support in`v-on`](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0014-drop-keycode-support.md)

- Can be detected and fixed by the[`vue/no-deprecated-v-on-number-modifiers`](https://eslint.vuejs.org/rules/no-deprecated-v-on-number-modifiers.html) ESLint rule

-`config.keyCode` can be supported in the compat build. It is also detectable with the[`vue/no-deprecated-vue-config-keycodes`](https://eslint.vuejs.org/rules/no-deprecated-vue-config-keycodes.html) ESLint rule

-🟢[RFC19: Remove`data` object declaration](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0019-remove-data-object-declaration.md)

-[RFC19: Remove`data` object declaration](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0019-remove-data-object-declaration.md)

- Can be detected and fixed by the[`vue/no-shared-component-data`](https://eslint.vuejs.org/rules/no-shared-component-data.html) and the[`vue/no-deprecated-data-object-declaration`](https://eslint.vuejs.org/rules/no-deprecated-data-object-declaration.html) ESLint rules

-🟢[RFC01: New slot syntax](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0001-new-slot-syntax.md) and[RFC06: Slots unification](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0006-slots-unification.md)

-🟢Can be detected and partially fixed by the[`vue/no-deprecated-slot-attribute`](https://eslint.vuejs.org/rules/no-deprecated-slot-attribute.html) and[`vue/no-deprecated-slot-scope-attribute`](https://eslint.vuejs.org/rules/no-deprecated-slot-scope-attribute.html)

-🟢During the transition period, with the 2 ESLint rules enabled, it will warn users when they use`this.$slots`, recommending`this.$scopedSlots` as a replacement

-🟢When upgrading to Vue 3, replace all`.$scopedSlots` occurrences with`.$slots` (should pass the abovementioned ESLint checks before running this codemod) (implemented as`scoped-slots-to-slots`)

-🟠[RFC04: Global API treeshaking](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0004-global-api-treeshaking.md) &[RFC09: Global mounting/configuration API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0009-global-api-change.md)

-[RFC01: New slot syntax](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0001-new-slot-syntax.md) and[RFC06: Slots unification](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0006-slots-unification.md)

- Can be detected and partially fixed by the[`vue/no-deprecated-slot-attribute`](https://eslint.vuejs.org/rules/no-deprecated-slot-attribute.html) and[`vue/no-deprecated-slot-scope-attribute`](https://eslint.vuejs.org/rules/no-deprecated-slot-scope-attribute.html)

- During the transition period, with the 2 ESLint rules enabled, it will warn users when they use`this.$slots`, recommending`this.$scopedSlots` as a replacement

- When upgrading to Vue 3, replace all`.$scopedSlots` occurrences with`.$slots` (should pass the abovementioned ESLint checks before running this codemod) (implemented as`scoped-slots-to-slots`)

-[RFC04: Global API treeshaking](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0004-global-api-treeshaking.md) &[RFC09: Global mounting/configuration API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0009-global-api-change.md)

-**implemented as`new-global-api`**

-🟢`import Vue from 'vue'` ->`import * as Vue from 'vue'` (implemented as`vue-as-namespace-import`)

-🟢`Vue.extend` ->`defineComponent` (implemented as`define-component`)

-🟢`new Vue()` ->`Vue.createApp()` (implemented as`new-vue-to-create-app`)

-🟢`new Vue({ el })`,`new Vue().$mount` ->`Vue.createApp().mount`

-🟢`new HelloWorld({ el })`,`new HelloWorld().$mount` ->`createApp(HelloWorld).mount`

-🟢`render(h)` ->`render()` and`import { h } from 'vue'` (implemented as`remove-contextual-h-from-render`)

-🟢`Vue.config.productionTip` -> removed (implemented as`remove-production-tip`)

-🔵 Some global APIs now can only be used on the app instances, while it's possible to support the legacy usage in a compat build, we will provide a codemod to help migration. (`global-to-per-app-api`)

-`import Vue from 'vue'` ->`import * as Vue from 'vue'` (implemented as`vue-as-namespace-import`)

-`Vue.extend` ->`defineComponent` (implemented as`define-component`)

-`new Vue()` ->`Vue.createApp()` (implemented as`new-vue-to-create-app`)

-`new Vue({ el })`,`new Vue().$mount` ->`Vue.createApp().mount`

-`new HelloWorld({ el })`,`new HelloWorld().$mount` ->`createApp(HelloWorld).mount`

-`render(h)` ->`render()` and`import { h } from 'vue'` (implemented as`remove-contextual-h-from-render`)

-`Vue.config.productionTip` -> removed (implemented as`remove-production-tip`)

-🔴 Some global APIs now can only be used on the app instances, while it's possible to support the legacy usage in a compat build, we will provide a codemod to help migration. (`global-to-per-app-api`)

-`Vue.config`,`Vue.use`,`Vue.mixin`,`Vue.component`,`Vue.directive`, etc ->`app.**` (It's possible to provide a runtime compatibility layer for single-root apps)

-`Vue.prototype.customProperty` ->`app.config.globalProperties.customProperty`

-`Vue.config.ignoredElements` ->`app.config.isCustomElement`

2. If there's exactly one entry file and one root instance, but several other files are also using`Vue.*`, then transform the entry file to export the root instance, import it in other files and transform them with the imported root instance;

3. If there are more than one entry file or root instances, then the user needs to manually export the root instances, re-apply this codemod to those non-entry files with an argument designating the root instance.

- 🔵 Detect and warn on`optionMergeStrategies` behavior change

-🟠[RFC07: Functional and async components API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0007-functional-async-api-change.md)

-[RFC07: Functional and async components API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0007-functional-async-api-change.md)

- 🔵 a compatibility mode can be provided for functional components for one-at-a-time migration

-🟢Can be detected by the[`vue/no-deprecated-functional-template`](https://eslint.vuejs.org/rules/no-deprecated-functional-template.html) ESLint rule

- Can be detected by the[`vue/no-deprecated-functional-template`](https://eslint.vuejs.org/rules/no-deprecated-functional-template.html) ESLint rule

- 🔴 SFCs using`<template functional>` should be converted to normal SFCs

-🟠[RFC08: Render function API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0008-render-function-api-change.md)

-🟢Template users won't be affected

-🟠JSX plugin will be rewritten to cover most use cases (work-in-progress, available athttps://github.com/vueComponent/jsx/)

-[RFC08: Render function API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0008-render-function-api-change.md)

- Template users won't be affected

- JSX plugin will be rewritten to cover most use cases (work-in-progress, available athttps://github.com/vueComponent/jsx/)

- 🔴 For Users who manually write render functions using`h`

- 🔵 It's possible to provide a compat plugin that patches render functions and make them expose a 2.x compatible arguments, and can be turned off in each component for a one-at-a-time migration process.

- 🔴 It's also possible to provide a codemod that auto-converts`h` calls to use the new VNode data format, since the mapping is pretty mechanical.

- 🔴 Functional components using context will likely have to be manually migrated, but a similar adaptor can be provided.

-🟠[RFC12: Custom directive API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0012-custom-directive-api-change.md)

-🟢`bind` ->`beforeMount`

-🟢`inserted` ->`mounted`

-🟢remove`update` hook and insert a comment to note the user about the change

-🟢`componentUpdated` ->`updated`

-🟢`unbind` ->`unmounted`

-[RFC12: Custom directive API change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0012-custom-directive-api-change.md)

-`bind` ->`beforeMount`

-`inserted` ->`mounted`

- remove`update` hook and insert a comment to note the user about the change

-`componentUpdated` ->`updated`

-`unbind` ->`unmounted`

- 🔴 VNode interface change (a runtime compat plugin is also possible, see the notes for RFC08)

-🟠[RFC13: Composition API](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0013-composition-api.md)

-🟢`import ... from '@vue/composition-api'` ->`import ... from 'vue'` (implemented as`import-composition-api-from-vue`)

-🔴 Othersubtle differences between`@vue/composition-api`andtheVue 3 implementation.

-🟠[RFC16: Remove`inline-template`](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0016-remove-inline-templates.md)

-🟢Can be detected by the[`vue/no-deprecated-inline-template`](https://eslint.vuejs.org/rules/no-deprecated-inline-template.html) ESLint rule

-[RFC13: Composition API](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0013-composition-api.md)

-`import ... from '@vue/composition-api'` ->`import ... from 'vue'` (implemented as`import-composition-api-from-vue`)

-There are somesubtle differences betweenthe pluginand Vue 3 implementation, seehttps://github.com/vuejs/composition-api#limitations for more details.

-[RFC16: Remove`inline-template`](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0016-remove-inline-templates.md)

- Can be detected by the[`vue/no-deprecated-inline-template`](https://eslint.vuejs.org/rules/no-deprecated-inline-template.html) ESLint rule

- 🔴 Possible alternatives are addressed[in the RFC](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0016-remove-inline-templates.md#adoption-strategy)

-🟠[RFC25: Built-in`<Teleport>` component](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0025-teleport.md)

-🟢Can be detected by the[`vue/no-reserved-component-names`](https://eslint.vuejs.org/rules/no-reserved-component-names.html) ESLint rule

-[RFC25: Built-in`<Teleport>` component](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0025-teleport.md)

- Can be detected by the[`vue/no-reserved-component-names`](https://eslint.vuejs.org/rules/no-reserved-component-names.html) ESLint rule

- 🔴 A codemod can be implemented to rename all`<Teleport>` components to some other name like`<TeleportComp>`.

- 🔴[RFC26: New async component API](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0026-async-component-api.md)

- 🔵 In the compat build, it is possible to check the return value of functional components and warn legacy async components usage. This should cover all Promise-based use cases.

- 🔴[RFC30: Add`emits` component option](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0030-emits-option.md)

- There could be potential naming conflicts with existing component-level`emits` options, so we need to scan and warn on such usages

- To better utilize the new`emits` option, we can provide a codemod that automatically scans all instances of`$emit` calls in a component and generate the`emits` option

-🟢[Vuex 3.x to 4](https://github.com/vuejs/vuex/tree/4.0)

-[Vuex 3.x to 4](https://github.com/vuejs/vuex/tree/4.0)

-**implemented as in combination of`new-global-api` and`vuex-v4`**

-🟢`Vue.use(Vuex)` &`new Vue({ store })` ->`app.use(store)`

-🟢`new Store()` ->`createStore()`

-🟠[Vue Router 3.x to 4](https://github.com/vuejs/vue-router-next)

-`Vue.use(Vuex)` &`new Vue({ store })` ->`app.use(store)`

-`new Store()` ->`createStore()`

-[Vue Router 3.x to 4](https://github.com/vuejs/vue-router-next)

-**implemented as in combination of`new-global-api` and`vue-router-v4`**

-🟢`Vue.use(VueRouter)` &`new Vue({ router })` ->`app.use(router)`

-🟢`new VueRouter()` ->`createRouter()`

-🟢`mode: 'history', base: BASE_URL` etc. ->`history: createWebHistory(BASE_URL)` etc.

-`Vue.use(VueRouter)` &`new Vue({ router })` ->`app.use(router)`

-`new VueRouter()` ->`createRouter()`

-`mode: 'history', base: BASE_URL` etc. ->`history: createWebHistory(BASE_URL)` etc.

- 🔴[RFC21: Scoped slot API for`router-link`](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0021-router-link-scoped-slot.md)

- 🔴[RFC28: Change active and exact-active behavior for`router-link`](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0028-router-active-link.md)

- 🔴[`vue-class-component` 7.x to 8](https://github.com/vuejs/vue-class-component/issues/406)

- Seems no codemod or ESLint rule is applicable to this breaking change

-[RFC24: Attribute coercion behavior change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0024-attribute-coercion-behavior.md)

- Codemod is not likely to help in this case

- Subtle differences between`@vue/composition-api` and the Vue 3 implementation are listed in the[`@vue/composition-api` README](https://github.com/vuejs/composition-api#limitations)

There will be runtime warnings and ESLint rules to detect their usages.

Some of them can be automatically migrated with the help of codemods.

-🟢[RFC15: Remove filters](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0015-remove-filters.md)

-[RFC15: Remove filters](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0015-remove-filters.md)

- Can be detected by the[`vue/no-deprecated-filter`](https://eslint.vuejs.org/rules/no-deprecated-filter.html) ESLint rule

- 🔴[RFC18: Transition class name adjustments](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0018-transition-class-change.md)

- For`<transition>` components with custom`enter-class` or`leave-class`:

- Otherwise, there are two possible solutions:

- Change every`.v-enter` and`.v-leave` selector in the stylesheets to`.v-enter-from` and`.v-leave-from`

- Or, attach`enter-from-class="v-enter v-enter-from" leave-from-class="v-leave v-leave-from"` to these`<transition>` components. Users can delete these attributes after they updated the corresponding stylesheets

-🟠[RFC20: Events API Change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0020-events-api-change.md)

-🟢Can be detected by the[`vue/no-deprecated-events-api`](https://eslint.vuejs.org/rules/no-deprecated-events-api.html) ESLint rule

-[RFC20: Events API Change](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0020-events-api-change.md)

- Can be detected by the[`vue/no-deprecated-events-api`](https://eslint.vuejs.org/rules/no-deprecated-events-api.html) ESLint rule

- 🔴 A codemod can be implemented to use other libraries like[tiny-emitter](https://github.com/scottcorgan/tiny-emitter) for the events API

-🟢[RFC23-scoped-styles-changes](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0023-scoped-styles-changes.md)

-[RFC23-scoped-styles-changes](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0023-scoped-styles-changes.md)

- The new behavior should be opt-in

-🟠[RFC27: Custom Elements Interop Improvements](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0027-custom-elements-interop.md)

-[RFC27: Custom Elements Interop Improvements](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0027-custom-elements-interop.md)

- (Covered by the Global API RFCs):`Vue.config.ignoredElements` ->`app.config.isCustomElement`

- 🔴 Vue 2 non-`<component>` tags with`is` usage ->

-`<component is>` (for SFC templates).

-`v-is` (for in-DOM templates).

-🟢The[`vue/no-deprecated-html-element-is`](https://eslint.vuejs.org/rules/no-deprecated-html-element-is.html) ESLint rule can be used to detect usage for`is` usage on built-in HTML tags.

- The[`vue/no-deprecated-html-element-is`](https://eslint.vuejs.org/rules/no-deprecated-html-element-is.html) ESLint rule can be used to detect usage for`is` usage on built-in HTML tags.