Require key for conditionally rendered repeated components

docs/rules/index.md

@@ -276,6 +276,7 @@ For example:
 | [vue/sort-keys](./sort-keys.md) | enforce sort-keys in a manner that is compatible with order-in-components |  | :hammer: |
 | [vue/static-class-names-order](./static-class-names-order.md) | enforce static class names order | :wrench: | :hammer: |
 | [vue/v-for-delimiter-style](./v-for-delimiter-style.md) | enforce `v-for` directive's delimiter style | :wrench: | :lipstick: |
+| [vue/v-if-else-key](./v-if-else-key.md) | require key attribute for conditionally rendered repeated components | :wrench: | :warning: |
 | [vue/v-on-handler-style](./v-on-handler-style.md) | enforce writing style for handlers in `v-on` directives | :wrench: | :hammer: |
 | [vue/valid-define-options](./valid-define-options.md) | enforce valid `defineOptions` compiler macro |  | :warning: |
 

docs/rules/require-v-for-key.md

@@ -5,6 +5,7 @@ title: vue/require-v-for-key
 description: require `v-bind:key` with `v-for` directives
 since: v3.0.0
 ---
+
 # vue/require-v-for-key
 
 > require `v-bind:key` with `v-for` directives
@@ -20,12 +21,9 @@ This rule reports the elements which have `v-for` and do not have `v-bind:key` w
 ```vue
 <template>
   <!-- ✓ GOOD -->
-  <div
-    v-for="todo in todos"
-    :key="todo.id"
-  />
+  <div v-for="todo in todos" :key="todo.id" />
   <!-- ✗ BAD -->
-  <div v-for="todo in todos"/>
+  <div v-for="todo in todos" />
 </template>
 ```
 
@@ -43,8 +41,10 @@ Nothing.
 ## :couple: Related Rules
 
 - [vue/valid-v-for]
+- [vue/v-if-else-key]
 
 [vue/valid-v-for]: ./valid-v-for.md
+[vue/v-if-else-key]: ./v-if-else-key.md
 
 ## :books: Further Reading
 

docs/rules/v-if-else-key.md

@@ -0,0 +1,56 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/v-if-else-key
+description: require key attribute for conditionally rendered repeated components
+---
+
+# vue/v-if-else-key
+
+> require key attribute for conditionally rendered repeated components
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+- :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule.
+
+## :book: Rule Details
+
+This rule checks for components that are both repeated and conditionally rendered within the same scope. If such a component is found, the rule then checks for the presence of a 'key' directive. If the 'key' directive is missing, the rule issues a warning and offers a fix.
+
+This rule is not required in Vue 3, as the key is automatically assigned to the elements.
+
+<eslint-code-block fix :rules="{'vue/v-if-else-key': ['error']}">
+
+```vue
+<template>
+  <!-- ✓ GOOD -->
+  <my-component v-if="condition1" :key="one" />
+  <my-component v-else-if="condition2" :key="two" />
+  <my-component v-else :key="three" />
+
+  <!-- ✗ BAD -->
+  <my-component v-if="condition1" />
+  <my-component v-else-if="condition2" />
+  <my-component v-else />
+</template>
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## :couple: Related Rules
+
+- [vue/require-v-for-key]
+
+[vue/require-v-for-key]: ./require-v-for-key.md
+
+## :books: Further Reading
+
+- [Guide (for v2) - v-if without key](https://v2.vuejs.org/v2/style-guide/#v-if-v-else-if-v-else-without-key-use-with-caution)
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/v-if-else-key.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/v-if-else-key.js)

lib/index.js

@@ -215,6 +215,7 @@ module.exports = {
     'use-v-on-exact': require('./rules/use-v-on-exact'),
     'v-bind-style': require('./rules/v-bind-style'),
     'v-for-delimiter-style': require('./rules/v-for-delimiter-style'),
+    'v-if-else-key': require('./rules/v-if-else-key'),
     'v-on-event-hyphenation': require('./rules/v-on-event-hyphenation'),
     'v-on-function-call': require('./rules/v-on-function-call'),
     'v-on-handler-style': require('./rules/v-on-handler-style'),