Add vue/script-setup-uses-vars rule

docs/.vuepress/components/eslint-code-block.vue

@@ -135,6 +135,7 @@ export default {
       linter.defineRule(`vue/${ruleId}`, rules[ruleId])
     }
     linter.defineRule('no-undef', coreRules['no-undef'])
+    linter.defineRule('no-unused-vars', coreRules['no-unused-vars'])
 
     linter.defineParser('vue-eslint-parser', { parseForESLint })
   }

docs/rules/README.md

@@ -25,6 +25,7 @@ Enforce all the rules in this category, as well as all higher priority rules, wi
 |:--------|:------------|:---|
 | [vue/comment-directive](./comment-directive.md) | support comment-directives in `<template>` |  |
 | [vue/jsx-uses-vars](./jsx-uses-vars.md) | prevent variables used in JSX to be marked as unused |  |
+| [vue/script-setup-uses-vars](./script-setup-uses-vars.md) | prevent `<script setup>` variables used in `<template>` to be marked as unused |  |
 
 ## Priority A: Essential (Error Prevention) <badge text="for Vue.js 3.x" vertical="middle">for Vue.js 3.x</badge>
 

docs/rules/jsx-uses-vars.md

@@ -38,6 +38,11 @@ After turning on, `HelloWorld` is being marked as used and `no-unused-vars` rule
 
 If you are not using JSX or if you do not use the `no-unused-vars` rule then you can disable this rule.
 
+## :couple: Related Rules
+
+- [vue/script-setup-uses-vars](./script-setup-uses-vars.md)
+- [no-unused-vars](https://eslint.org/docs/rules/no-unused-vars)
+
 ## :rocket: Version
 
 This rule was introduced in eslint-plugin-vue v2.0.0

docs/rules/script-setup-uses-vars.md

@@ -0,0 +1,64 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/script-setup-uses-vars
+description: prevent `<script setup>` variables used in `<template>` to be marked as unused
+---
+# vue/script-setup-uses-vars
+
+> prevent `<script setup>` variables used in `<template>` to be marked as unused
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+- :gear: This rule is included in all of `"plugin:vue/base"`, `"plugin:vue/essential"`, `"plugin:vue/vue3-essential"`, `"plugin:vue/strongly-recommended"`, `"plugin:vue/vue3-strongly-recommended"`, `"plugin:vue/recommended"` and `"plugin:vue/vue3-recommended"`.
+
+ESLint `no-unused-vars` rule does not detect variables in `<script setup>` used in `<template>`.
+This rule will find variables in `<script setup>` used in `<template>` and mark them as used.
+
+This rule only has an effect when the `no-unused-vars` rule is enabled.
+
+## :book: Rule Details
+
+Without this rule this code triggers warning:
+
+<eslint-code-block :rules="{'vue/script-setup-uses-vars': ['error'], 'no-unused-vars': ['error']}">
+
+```vue
+<script setup>
+  // imported components are also directly usable in template
+  import Foo from './Foo.vue'
+  import { ref } from 'vue'
+
+  // write Composition API code just like in a normal setup()
+  // but no need to manually return everything
+  const count = ref(0)
+  const inc = () => {
+    count.value++
+  }
+</script>
+
+<template>
+  <Foo :count="count" @click="inc" />
+</template>
+```
+
+</eslint-code-block>
+
+After turning on, `Foo` is being marked as used and `no-unused-vars` rule doesn't report an issue.
+
+## :mute: When Not To Use It
+
+If you are not using `<script setup>` or if you do not use the `no-unused-vars` rule then you can disable this rule.
+
+## :couple: Related Rules
+
+- [vue/jsx-uses-vars](./jsx-uses-vars.md)
+- [no-unused-vars](https://eslint.org/docs/rules/no-unused-vars)
+
+## :books: Further Reading
+
+- [Vue RFCs - 0040-script-setup](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0040-script-setup.md)
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/script-setup-uses-vars.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/script-setup-uses-vars.js)

lib/configs/base.js

@@ -16,6 +16,7 @@ module.exports = {
   plugins: ['vue'],
   rules: {
     'vue/comment-directive': 'error',
-    'vue/jsx-uses-vars': 'error'
+    'vue/jsx-uses-vars': 'error',
+    'vue/script-setup-uses-vars': 'error'
   }
 }

lib/index.js

@@ -155,6 +155,7 @@ module.exports = {
     'return-in-computed-property': require('./rules/return-in-computed-property'),
     'return-in-emits-validator': require('./rules/return-in-emits-validator'),
     'script-indent': require('./rules/script-indent'),
+    'script-setup-uses-vars': require('./rules/script-setup-uses-vars'),
     'singleline-html-element-content-newline': require('./rules/singleline-html-element-content-newline'),
     'sort-keys': require('./rules/sort-keys'),
     'space-in-parens': require('./rules/space-in-parens'),

lib/rules/no-reserved-component-names.js

@@ -10,6 +10,13 @@ const casing = require('../utils/casing')
 const htmlElements = require('../utils/html-elements.json')
 const deprecatedHtmlElements = require('../utils/deprecated-html-elements.json')
 const svgElements = require('../utils/svg-elements.json')
+const RESERVED_NAMES_IN_VUE = new Set(
+  require('../utils/vue2-builtin-components')
+)
+
+const RESERVED_NAMES_IN_VUE3 = new Set(
+  require('../utils/vue3-builtin-components')
+)
 
 const kebabCaseElements = [
   'annotation-xml',
@@ -22,17 +29,6 @@ const kebabCaseElements = [
   'missing-glyph'
 ]
 
-// https://vuejs.org/v2/api/index.html#Built-In-Components
-const vueBuiltInComponents = [
-  'component',
-  'transition',
-  'transition-group',
-  'keep-alive',
-  'slot'
-]
-
-const vue3BuiltInComponents = ['teleport', 'suspense']
-
 /** @param {string} word  */
 function isLowercase(word) {
   return /^[a-z]*$/.test(word)
@@ -42,15 +38,6 @@ const RESERVED_NAMES_IN_HTML = new Set([
   ...htmlElements,
   ...htmlElements.map(casing.capitalize)
 ])
-const RESERVED_NAMES_IN_VUE = new Set([
-  ...vueBuiltInComponents,
-  ...vueBuiltInComponents.map(casing.pascalCase)
-])
-const RESERVED_NAMES_IN_VUE3 = new Set([
-  ...RESERVED_NAMES_IN_VUE,
-  ...vue3BuiltInComponents,
-  ...vue3BuiltInComponents.map(casing.pascalCase)
-])
 const RESERVED_NAMES_IN_OTHERS = new Set([
   ...deprecatedHtmlElements,
   ...deprecatedHtmlElements.map(casing.capitalize),

lib/rules/no-unregistered-components.js

@@ -15,15 +15,6 @@ const casing = require('../utils/casing')
 // Rule helpers
 // ------------------------------------------------------------------------------
 
-const VUE_BUILT_IN_COMPONENTS = [
-  'component',
-  'suspense',
-  'teleport',
-  'transition',
-  'transition-group',
-  'keep-alive',
-  'slot'
-]
 /**
  * Check whether the given node is a built-in component or not.
  *
@@ -37,7 +28,7 @@ const isBuiltInComponent = (node) => {
   return (
     utils.isHtmlElementNode(node) &&
     !utils.isHtmlWellKnownElementName(node.rawName) &&
-    VUE_BUILT_IN_COMPONENTS.indexOf(rawName) > -1
+    utils.isBuiltInComponentName(rawName)
   )
 }
 

lib/rules/script-setup-uses-vars.js

@@ -0,0 +1,115 @@
+/**
+ * @author Yosuke Ota
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const utils = require('../utils')
+const casing = require('../utils/casing')
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description:
+        'prevent `<script setup>` variables used in `<template>` to be marked as unused', // eslint-disable-line consistent-docs-description
+      categories: ['base'],
+      url: 'https://eslint.vuejs.org/rules/script-setup-uses-vars.html'
+    },
+    schema: []
+  },
+  /**
+   * @param {RuleContext} context - The rule context.
+   * @returns {RuleListener} AST event handlers.
+   */
+  create(context) {
+    if (!utils.isScriptSetup(context)) {
+      return {}
+    }
+    /** @type {Set<string>} */
+    const scriptVariableNames = new Set()
+    const globalScope = context.getSourceCode().scopeManager.globalScope
+    if (globalScope) {
+      for (const variable of globalScope.variables) {
+        scriptVariableNames.add(variable.name)
+      }
+      const moduleScope = globalScope.childScopes.find(
+        (scope) => scope.type === 'module'
+      )
+      for (const variable of (moduleScope && moduleScope.variables) || []) {
+        scriptVariableNames.add(variable.name)
+      }
+    }
+
+    /**
+     * `casing.camelCase()` converts the beginning to lowercase,
+     * but does not convert the case of the beginning character when converting with Vue3.
+     * @see https://github.com/vuejs/vue-next/blob/1ffd48a2f5fd3eead3ea29dae668b7ed1c6f6130/packages/shared/src/index.ts#L116
+     * @param {string} str
+     */
+    function camelize(str) {
+      return str.replace(/-(\w)/g, (_, c) => (c ? c.toUpperCase() : ''))
+    }
+    /**
+     * @see https://github.com/vuejs/vue-next/blob/1ffd48a2f5fd3eead3ea29dae668b7ed1c6f6130/packages/compiler-core/src/transforms/transformElement.ts#L321
+     * @param {string} name
+     */
+    function markElementVariableAsUsed(name) {
+      if (scriptVariableNames.has(name)) {
+        context.markVariableAsUsed(name)
+      }
+      const camelName = camelize(name)
+      if (scriptVariableNames.has(camelName)) {
+        context.markVariableAsUsed(camelName)
+      }
+      const pascalName = casing.capitalize(camelName)
+      if (scriptVariableNames.has(pascalName)) {
+        context.markVariableAsUsed(pascalName)
+      }
+    }
+
+    return utils.defineTemplateBodyVisitor(
+      context,
+      {
+        VExpressionContainer(node) {
+          for (const ref of node.references.filter(
+            (ref) => ref.variable == null
+          )) {
+            context.markVariableAsUsed(ref.id.name)
+          }
+        },
+        VElement(node) {
+          if (
+            (!utils.isHtmlElementNode(node) && !utils.isSvgElementNode(node)) ||
+            (node.rawName === node.name &&
+              (utils.isHtmlWellKnownElementName(node.rawName) ||
+                utils.isSvgWellKnownElementName(node.rawName))) ||
+            utils.isBuiltInComponentName(node.rawName)
+          ) {
+            return
+          }
+          markElementVariableAsUsed(node.rawName)
+        },
+        /** @param {VDirective} node */
+        'VAttribute[directive=true]'(node) {
+          if (utils.isBuiltInDirectiveName(node.key.name.name)) {
+            return
+          }
+          markElementVariableAsUsed(`v-${node.key.name.rawName}`)
+        }
+      },
+      undefined,
+      {
+        templateBodyTriggerSelector: 'Program'
+      }
+    )
+  }
+}