Add vue/valid-define-emits rule (#1561)

docs/rules/README.md

@@ -332,6 +332,7 @@ For example:
 | [vue/v-for-delimiter-style](./v-for-delimiter-style.md) | enforce `v-for` directive's delimiter style | :wrench: |
 | [vue/v-on-event-hyphenation](./v-on-event-hyphenation.md) | enforce v-on event naming style on custom components in template | :wrench: |
 | [vue/v-on-function-call](./v-on-function-call.md) | enforce or forbid parentheses after method calls without arguments in `v-on` directives | :wrench: |
+| [vue/valid-define-emits](./valid-define-emits.md) | enforce valid `defineEmits` compiler macro |  |
 | [vue/valid-define-props](./valid-define-props.md) | enforce valid `defineProps` compiler macro |  |
 | [vue/valid-next-tick](./valid-next-tick.md) | enforce valid `nextTick` function calls | :wrench: |
 

docs/rules/valid-define-emits.md

@@ -0,0 +1,133 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/valid-define-emits
+description: enforce valid `defineEmits` compiler macro
+---
+# vue/valid-define-emits
+
+> enforce valid `defineEmits` compiler macro
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+
+This rule checks whether `defineEmits` compiler macro is valid.
+
+## :book: Rule Details
+
+This rule reports `defineEmits` compiler macros in the following cases:
+
+- `defineEmits` are referencing locally declared variables.
+- `defineEmits` has both a literal type and an argument. e.g. `defineEmits<(e: 'foo')=>void>(['bar'])`
+- `defineEmits` has been called multiple times.
+- Custom events are defined in both `defineEmits` and `export default {}`.
+- Custom events are not defined in either `defineEmits` or `export default {}`.
+
+<eslint-code-block :rules="{'vue/valid-define-emits': ['error']}">
+
+```vue
+<script setup>
+  /* ✓ GOOD */
+  defineEmits({ notify: null })
+</script>
+```
+
+</eslint-code-block>
+
+<eslint-code-block :rules="{'vue/valid-define-emits': ['error']}">
+
+```vue
+<script setup>
+  /* ✓ GOOD */
+  defineEmits(['notify'])
+</script>
+```
+
+</eslint-code-block>
+
+```vue
+<script setup lang="ts">
+  /* ✓ GOOD */
+  defineEmits<(e: 'notify')=>void>()
+</script>
+```
+
+<eslint-code-block :rules="{'vue/valid-define-emits': ['error']}">
+
+```vue
+<script>
+  const def = { notify: null }
+</script>
+<script setup>
+  /* ✓ GOOD */
+  defineEmits(def)
+</script>
+```
+
+</eslint-code-block>
+
+<eslint-code-block :rules="{'vue/valid-define-emits': ['error']}">
+
+```vue
+<script setup>
+  /* ✗ BAD */
+  const def = { notify: null }
+  defineEmits(def)
+</script>
+```
+
+</eslint-code-block>
+
+```vue
+<script setup lang="ts">
+  /* ✗ BAD */
+  defineEmits<(e: 'notify')=>void>({ submit: null })
+</script>
+```
+
+<eslint-code-block :rules="{'vue/valid-define-emits': ['error']}">
+
+```vue
+<script setup>
+  /* ✗ BAD */
+  defineEmits({ notify: null })
+  defineEmits({ submit: null })
+</script>
+```
+
+</eslint-code-block>
+
+<eslint-code-block :rules="{'vue/valid-define-emits': ['error']}">
+
+```vue
+<script>
+  export default {
+    emits: { notify: null }
+  }
+</script>
+<script setup>
+  /* ✗ BAD */
+  defineEmits({ submit: null })
+</script>
+```
+
+</eslint-code-block>
+
+<eslint-code-block :rules="{'vue/valid-define-emits': ['error']}">
+
+```vue
+<script setup>
+  /* ✗ BAD */
+  defineEmits()
+</script>
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/valid-define-emits.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/valid-define-emits.js)

lib/index.js

@@ -172,6 +172,7 @@ module.exports = {
     'v-on-function-call': require('./rules/v-on-function-call'),
     'v-on-style': require('./rules/v-on-style'),
     'v-slot-style': require('./rules/v-slot-style'),
+    'valid-define-emits': require('./rules/valid-define-emits'),
     'valid-define-props': require('./rules/valid-define-props'),
     'valid-next-tick': require('./rules/valid-next-tick'),
     'valid-template-root': require('./rules/valid-template-root'),

lib/rules/valid-define-emits.js

@@ -0,0 +1,144 @@
+/**
+ * @author Yosuke Ota <https://github.com/ota-meshi>
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+const { findVariable } = require('eslint-utils')
+const utils = require('../utils')
+
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'enforce valid `defineEmits` compiler macro',
+      // TODO Switch in the major version.
+      // categories: ['vue3-essential'],
+      categories: undefined,
+      url: 'https://eslint.vuejs.org/rules/valid-define-emits.html'
+    },
+    fixable: null,
+    schema: [],
+    messages: {
+      hasTypeAndArg: '`defineEmits` has both a type-only emit and an argument.',
+      referencingLocally:
+        '`defineEmits` are referencing locally declared variables.',
+      multiple: '`defineEmits` has been called multiple times.',
+      notDefined: 'Custom events are not defined.',
+      definedInBoth:
+        'Custom events are defined in both `defineEmits` and `export default {}`.'
+    }
+  },
+  /** @param {RuleContext} context */
+  create(context) {
+    const scriptSetup = utils.getScriptSetupElement(context)
+    if (!scriptSetup) {
+      return {}
+    }
+
+    /** @type {Set<Expression | SpreadElement>} */
+    const emitsDefExpressions = new Set()
+    let hasDefaultExport = false
+    /** @type {CallExpression[]} */
+    const defineEmitsNodes = []
+    /** @type {CallExpression | null} */
+    let emptyDefineEmits = null
+
+    return utils.compositingVisitors(
+      utils.defineScriptSetupVisitor(context, {
+        onDefineEmitsEnter(node) {
+          defineEmitsNodes.push(node)
+
+          if (node.arguments.length >= 1) {
+            if (node.typeParameters && node.typeParameters.params.length >= 1) {
+              // `defineEmits` has both a literal type and an argument.
+              context.report({
+                node,
+                messageId: 'hasTypeAndArg'
+              })
+              return
+            }
+
+            emitsDefExpressions.add(node.arguments[0])
+          } else {
+            if (
+              !node.typeParameters ||
+              node.typeParameters.params.length === 0
+            ) {
+              emptyDefineEmits = node
+            }
+          }
+        },
+        Identifier(node) {
+          for (const def of emitsDefExpressions) {
+            if (utils.inRange(def.range, node)) {
+              const variable = findVariable(context.getScope(), node)
+              if (
+                variable &&
+                variable.references.some((ref) => ref.identifier === node)
+              ) {
+                if (
+                  variable.defs.length &&
+                  variable.defs.every((def) =>
+                    utils.inRange(scriptSetup.range, def.name)
+                  )
+                ) {
+                  //`defineEmits` are referencing locally declared variables.
+                  context.report({
+                    node,
+                    messageId: 'referencingLocally'
+                  })
+                }
+              }
+            }
+          }
+        }
+      }),
+      utils.defineVueVisitor(context, {
+        onVueObjectEnter(node, { type }) {
+          if (type !== 'export' || utils.inRange(scriptSetup.range, node)) {
+            return
+          }
+
+          hasDefaultExport = Boolean(utils.findProperty(node, 'emits'))
+        }
+      }),
+      {
+        'Program:exit'() {
+          if (!defineEmitsNodes.length) {
+            return
+          }
+          if (defineEmitsNodes.length > 1) {
+            // `defineEmits` has been called multiple times.
+            for (const node of defineEmitsNodes) {
+              context.report({
+                node,
+                messageId: 'multiple'
+              })
+            }
+            return
+          }
+          if (emptyDefineEmits) {
+            if (!hasDefaultExport) {
+              // Custom events are not defined.
+              context.report({
+                node: emptyDefineEmits,
+                messageId: 'notDefined'
+              })
+            }
+          } else {
+            if (hasDefaultExport) {
+              // Custom events are defined in both `defineEmits` and `export default {}`.
+              for (const node of defineEmitsNodes) {
+                context.report({
+                  node,
+                  messageId: 'definedInBoth'
+                })
+              }
+            }
+          }
+        }
+      }
+    )
+  }
+}