Add vue/experimental-script-setup-vars rule

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

@@ -62,6 +62,7 @@ export default {
     config() {
       return {
         globals: {
+          console: false,
           // ES2015 globals
           ArrayBuffer: false,
           DataView: false,
@@ -121,8 +122,13 @@ export default {
 
   async mounted() {
     // Load linter.
-    const [{ default: Linter }, { parseForESLint }] = await Promise.all([
+    const [
+      { default: Linter },
+      { default: noUndefRule },
+      { parseForESLint }
+    ] = await Promise.all([
       import('eslint4b/dist/linter'),
+      import('eslint/lib/rules/no-undef'),
       import('espree').then(() => import('vue-eslint-parser'))
     ])
 
@@ -131,6 +137,7 @@ export default {
     for (const ruleId of Object.keys(rules)) {
       linter.defineRule(`vue/${ruleId}`, rules[ruleId])
     }
+    linter.defineRule('no-undef', noUndefRule)
 
     linter.defineParser('vue-eslint-parser', { parseForESLint })
   }

docs/rules/README.md

@@ -24,6 +24,7 @@ Enforce all the rules in this category, as well as all higher priority rules, wi
 | Rule ID | Description |    |
 |:--------|:------------|:---|
 | [vue/comment-directive](./comment-directive.md) | support comment-directives in `<template>` |  |
+| [vue/experimental-script-setup-vars](./experimental-script-setup-vars.md) | prevent variables defined in `<script setup>` to be marked as undefined |  |
 | [vue/jsx-uses-vars](./jsx-uses-vars.md) | prevent variables used in JSX 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/experimental-script-setup-vars.md

@@ -0,0 +1,42 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/experimental-script-setup-vars
+description: prevent variables defined in `<script setup>` to be marked as undefined
+---
+# vue/experimental-script-setup-vars
+> prevent variables defined in `<script setup>` to be marked as undefined
+
+- :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"`.
+
+:::warning
+This rule is an experimental rule. It may be removed without notice.
+:::
+
+This rule will find variables defined in `<script setup="args">` and mark them as defined variables.
+
+This rule only has an effect when the `no-undef` rule is enabled.
+
+## :book: Rule Details
+
+Without this rule this code triggers warning:
+
+<eslint-code-block :rules="{'no-undef': ['error'], 'vue/experimental-script-setup-vars': ['error']}">
+
+```vue
+<script setup="props, { emit }">
+import { watchEffect } from 'vue'
+
+watchEffect(() => console.log(props.msg))
+emit('foo')
+</script>
+```
+
+</eslint-code-block>
+
+After turning on, `props` and `emit` are being marked as defined and `no-undef` rule doesn't report an issue.
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/experimental-script-setup-vars.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/experimental-script-setup-vars.js)

lib/configs/base.js

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

lib/index.js

@@ -25,6 +25,7 @@ module.exports = {
     'dot-location': require('./rules/dot-location'),
     'dot-notation': require('./rules/dot-notation'),
     eqeqeq: require('./rules/eqeqeq'),
+    'experimental-script-setup-vars': require('./rules/experimental-script-setup-vars'),
     'func-call-spacing': require('./rules/func-call-spacing'),
     'html-closing-bracket-newline': require('./rules/html-closing-bracket-newline'),
     'html-closing-bracket-spacing': require('./rules/html-closing-bracket-spacing'),

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

@@ -0,0 +1,228 @@
+/**
+ * @fileoverview prevent variables defined in `<script setup>` to be marked as undefined
+ * @author Yosuke Ota
+ */
+'use strict'
+
+const Module = require('module')
+const path = require('path')
+const utils = require('../utils')
+const AST = require('vue-eslint-parser').AST
+
+const ecmaVersion = 2020
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description:
+        'prevent variables defined in `<script setup>` to be marked as undefined', // eslint-disable-line consistent-docs-description
+      categories: ['base'],
+      url: 'https://eslint.vuejs.org/rules/experimental-script-setup-vars.html'
+    },
+    schema: []
+  },
+  /**
+   * @param {RuleContext} context - The rule context.
+   * @returns {RuleListener} AST event handlers.
+   */
+  create(context) {
+    const documentFragment =
+      context.parserServices.getDocumentFragment &&
+      context.parserServices.getDocumentFragment()
+    if (!documentFragment) {
+      return {}
+    }
+    const sourceCode = context.getSourceCode()
+    const scriptElement = documentFragment.children
+      .filter(utils.isVElement)
+      .find(
+        (element) =>
+          element.name === 'script' &&
+          element.range[0] <= sourceCode.ast.range[0] &&
+          sourceCode.ast.range[1] <= element.range[1]
+      )
+    if (!scriptElement) {
+      return {}
+    }
+    const setupAttr = utils.getAttribute(scriptElement, 'setup')
+    if (!setupAttr || !setupAttr.value) {
+      return {}
+    }
+    const value = setupAttr.value.value
+
+    let eslintScope
+    try {
+      eslintScope = getESLintModule('eslint-scope', () =>
+        // @ts-ignore
+        require('eslint-scope')
+      )
+    } catch (_e) {
+      context.report({
+        node: setupAttr,
+        message: 'Can not be resolved eslint-scope.'
+      })
+      return {}
+    }
+    let espree
+    try {
+      espree = getESLintModule('espree', () =>
+        // @ts-ignore
+        require('espree')
+      )
+    } catch (_e) {
+      context.report({
+        node: setupAttr,
+        message: 'Can not be resolved espree.'
+      })
+      return {}
+    }
+
+    const globalScope = sourceCode.scopeManager.scopes[0]
+
+    /** @type {string[]} */
+    let vars
+    try {
+      vars = parseSetup(value, espree, eslintScope)
+    } catch (_e) {
+      context.report({
+        node: setupAttr.value,
+        message: 'Parsing error.'
+      })
+      return {}
+    }
+
+    // Define configured global variables.
+    for (const id of vars) {
+      const tempVariable = globalScope.set.get(id)
+
+      /** @type {Variable} */
+      let variable
+      if (!tempVariable) {
+        variable = new eslintScope.Variable(id, globalScope)
+
+        globalScope.variables.push(variable)
+        globalScope.set.set(id, variable)
+      } else {
+        variable = tempVariable
+      }
+
+      variable.eslintImplicitGlobalSetting = 'readonly'
+      variable.eslintExplicitGlobal = undefined
+      variable.eslintExplicitGlobalComments = undefined
+      variable.writeable = false
+    }
+
+    /*
+     * "through" contains all references which definitions cannot be found.
+     * Since we augment the global scope using configuration, we need to update
+     * references and remove the ones that were added by configuration.
+     */
+    globalScope.through = globalScope.through.filter((reference) => {
+      const name = reference.identifier.name
+      const variable = globalScope.set.get(name)
+
+      if (variable) {
+        /*
+         * Links the variable and the reference.
+         * And this reference is removed from `Scope#through`.
+         */
+        reference.resolved = variable
+        variable.references.push(reference)
+
+        return false
+      }
+
+      return true
+    })
+
+    return {}
+  }
+}
+
+/**
+ * @param {string} code
+ * @param {any} espree
+ * @param {any} eslintScope
+ * @returns {string[]}
+ */
+function parseSetup(code, espree, eslintScope) {
+  /** @type {Program} */
+  const ast = espree.parse(`(${code})=>{}`, { ecmaVersion })
+  const result = eslintScope.analyze(ast, {
+    ignoreEval: true,
+    nodejsScope: false,
+    ecmaVersion,
+    sourceType: 'script',
+    fallback: AST.getFallbackKeys
+  })
+
+  const variables = /** @type {Variable[]} */ (result.globalScope.childScopes[0]
+    .variables)
+
+  return variables.map((v) => v.name)
+}
+
+const createRequire =
+  // Added in v12.2.0
+  Module.createRequire ||
+  // Added in v10.12.0, but deprecated in v12.2.0.
+  Module.createRequireFromPath ||
+  // Polyfill - This is not executed on the tests on node@>=10.
+  /**
+   * @param {string} filename
+   */
+  function (filename) {
+    const mod = new Module(filename)
+
+    mod.filename = filename
+    // @ts-ignore
+    mod.paths = Module._nodeModulePaths(path.dirname(filename))
+    // @ts-ignore
+    mod._compile('module.exports = require;', filename)
+    return mod.exports
+  }
+
+/** @type { { 'espree'?: any, 'eslint-scope'?: any } } */
+const modulesCache = {}
+
+/**
+ * @param {string} p
+ */
+function isLinterPath(p) {
+  return (
+    // ESLint 6 and above
+    p.includes(`eslint${path.sep}lib${path.sep}linter${path.sep}linter.js`) ||
+    // ESLint 5
+    p.includes(`eslint${path.sep}lib${path.sep}linter.js`)
+  )
+}
+
+/**
+ * Load module from the loaded ESLint.
+ * If the loaded ESLint was not found, just returns `fallback()`.
+ * @param {'espree' | 'eslint-scope'} name
+ * @param { () => any } fallback
+ */
+function getESLintModule(name, fallback) {
+  if (!modulesCache[name]) {
+    // Lookup the loaded eslint
+    const linterPath = Object.keys(require.cache).find(isLinterPath)
+    if (linterPath) {
+      try {
+        modulesCache[name] = createRequire(linterPath)(name)
+      } catch (_e) {
+        // ignore
+      }
+    }
+    if (!modulesCache[name]) {
+      modulesCache[name] = fallback()
+    }
+  }
+
+  return modulesCache[name]
+}

tests/lib/rules/experimental-script-setup-vars.js

@@ -0,0 +1,58 @@
+/**
+ * @author Yosuke Ota
+ */
+'use strict'
+
+const { RuleTester } = require('eslint')
+const rule = require('../../../lib/rules/experimental-script-setup-vars')
+
+const tester = new RuleTester({
+  parser: require.resolve('vue-eslint-parser'),
+  parserOptions: { ecmaVersion: 2020, sourceType: 'module' }
+})
+
+tester.run('experimental-script-setup-vars', rule, {
+  valid: [
+    `
+    <script setup="props, { emit }">
+    import { watchEffect } from 'vue'
+
+    watchEffect(() => console.log(props.msg))
+    emit('foo')
+    </script>`,
+    `
+    <script setup>
+    export let count = 1
+    </script>`,
+    `
+    <script>
+    import { watchEffect } from 'vue'
+
+    export default {
+      setup (props, { emit }) {
+        watchEffect(() => console.log(props.msg))
+        emit('foo')
+        return {}
+      }
+    }
+    </script>`,
+    `
+    <template>
+      <div />
+    </template>`
+  ],
+  invalid: [
+    {
+      code: `
+      <script setup="a - b">
+      </script>
+      `,
+      errors: [
+        {
+          message: 'Parsing error.',
+          line: 2
+        }
+      ]
+    }
+  ]
+})