New: Add vue/no-watch-after-await rule (#1068)

* New: Add `vue/no-watch-after-await` rule

* Add check for watchEffect.

* Update vue/no-watch-after-await

docs/rules/README.md

@@ -61,6 +61,7 @@ Enforce all the rules in this category, as well as all higher priority rules, wi
 | [vue/no-unused-components](./no-unused-components.md) | disallow registering components that are not used inside templates |  |
 | [vue/no-unused-vars](./no-unused-vars.md) | disallow unused variable definitions of v-for directives or scope attributes |  |
 | [vue/no-use-v-if-with-v-for](./no-use-v-if-with-v-for.md) | disallow use v-if on the same element as v-for |  |
+| [vue/no-watch-after-await](./no-watch-after-await.md) | disallow asynchronously registered `watch` |  |
 | [vue/require-component-is](./require-component-is.md) | require `v-bind:is` of `<component>` elements |  |
 | [vue/require-prop-type-constructor](./require-prop-type-constructor.md) | require prop type to be a constructor | :wrench: |
 | [vue/require-render-return](./require-render-return.md) | enforce render function to always return value |  |

docs/rules/no-watch-after-await.md

@@ -0,0 +1,73 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/no-watch-after-await
+description: disallow asynchronously registered `watch`
+---
+# vue/no-watch-after-await
+> disallow asynchronously registered `watch`
+
+- :gear: This rule is included in all of `"plugin:vue/vue3-essential"`, `"plugin:vue/vue3-strongly-recommended"` and `"plugin:vue/vue3-recommended"`.
+
+## :book: Rule Details
+
+This rule reports the `watch()` after `await` expression.  
+In `setup()` function, `watch()` should be registered synchronously.
+
+<eslint-code-block :rules="{'vue/no-watch-after-await': ['error']}">
+
+```vue
+<script>
+import { watch } from 'vue'
+export default {
+  async setup() {
+    /* ✓ GOOD */
+    watch(watchSource, () => { /* ... */ })
+
+    await doSomething()
+
+    /* ✗ BAD */
+    watch(watchSource, () => { /* ... */ })
+  }
+}
+</script>
+```
+
+</eslint-code-block>
+
+This rule is not reported when using the stop handle.
+
+<eslint-code-block :rules="{'vue/no-watch-after-await': ['error']}">
+
+```vue
+<script>
+import { watch } from 'vue'
+export default {
+  async setup() {
+    await doSomething()
+
+    /* ✓ GOOD */
+    const stopHandle = watch(watchSource, () => { /* ... */ })
+
+    // later
+    stopHandle()
+  }
+}
+</script>
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## :books: Further reading
+
+- [Vue RFCs - 0013-composition-api](https://github.com/vuejs/rfcs/blob/master/active-rfcs/0013-composition-api.md)
+- [Vue Composition API - API Reference - Stopping the Watcher](https://composition-api.vuejs.org/api.html#stopping-the-watcher)
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/no-watch-after-await.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/no-watch-after-await.js)

lib/configs/vue3-essential.js

@@ -29,6 +29,7 @@ module.exports = {
     'vue/no-unused-components': 'error',
     'vue/no-unused-vars': 'error',
     'vue/no-use-v-if-with-v-for': 'error',
+    'vue/no-watch-after-await': 'error',
     'vue/require-component-is': 'error',
     'vue/require-prop-type-constructor': 'error',
     'vue/require-render-return': 'error',

lib/index.js

@@ -75,6 +75,7 @@ module.exports = {
     'no-use-v-if-with-v-for': require('./rules/no-use-v-if-with-v-for'),
     'no-v-html': require('./rules/no-v-html'),
     'no-v-model-argument': require('./rules/no-v-model-argument'),
+    'no-watch-after-await': require('./rules/no-watch-after-await'),
     'object-curly-spacing': require('./rules/object-curly-spacing'),
     'order-in-components': require('./rules/order-in-components'),
     'padding-line-between-blocks': require('./rules/padding-line-between-blocks'),

lib/rules/no-watch-after-await.js

@@ -0,0 +1,137 @@
+/**
+ * @author Yosuke Ota
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+const { ReferenceTracker } = require('eslint-utils')
+const utils = require('../utils')
+
+function isMaybeUsedStopHandle (node) {
+  const parent = node.parent
+  if (parent) {
+    if (parent.type === 'VariableDeclarator') {
+      // var foo = watch()
+      return true
+    }
+    if (parent.type === 'AssignmentExpression') {
+      // foo = watch()
+      return true
+    }
+    if (parent.type === 'CallExpression') {
+      // foo(watch())
+      return true
+    }
+    if (parent.type === 'Property') {
+      // {foo: watch()}
+      return true
+    }
+    if (parent.type === 'ArrayExpression') {
+      // [watch()]
+      return true
+    }
+  }
+  return false
+}
+
+module.exports = {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description: 'disallow asynchronously registered `watch`',
+      categories: ['vue3-essential'],
+      url: 'https://eslint.vuejs.org/rules/no-watch-after-await.html'
+    },
+    fixable: null,
+    schema: [],
+    messages: {
+      forbidden: 'The `watch` after `await` expression are forbidden.'
+    }
+  },
+  create (context) {
+    const watchCallNodes = new Set()
+    const setupFunctions = new Map()
+    const forbiddenNodes = new Map()
+
+    function addForbiddenNode (property, node) {
+      let list = forbiddenNodes.get(property)
+      if (!list) {
+        list = []
+        forbiddenNodes.set(property, list)
+      }
+      list.push(node)
+    }
+
+    let scopeStack = { upper: null, functionNode: null }
+
+    return Object.assign(
+      {
+        'Program' () {
+          const tracker = new ReferenceTracker(context.getScope())
+          const traceMap = {
+            vue: {
+              [ReferenceTracker.ESM]: true,
+              watch: {
+                [ReferenceTracker.CALL]: true
+              },
+              watchEffect: {
+                [ReferenceTracker.CALL]: true
+              }
+            }
+          }
+
+          for (const { node } of tracker.iterateEsmReferences(traceMap)) {
+            watchCallNodes.add(node)
+          }
+        },
+        'Property[value.type=/^(Arrow)?FunctionExpression$/]' (node) {
+          if (utils.getStaticPropertyName(node) !== 'setup') {
+            return
+          }
+
+          setupFunctions.set(node.value, {
+            setupProperty: node,
+            afterAwait: false
+          })
+        },
+        ':function' (node) {
+          scopeStack = { upper: scopeStack, functionNode: node }
+        },
+        'AwaitExpression' () {
+          const setupFunctionData = setupFunctions.get(scopeStack.functionNode)
+          if (!setupFunctionData) {
+            return
+          }
+          setupFunctionData.afterAwait = true
+        },
+        'CallExpression' (node) {
+          const setupFunctionData = setupFunctions.get(scopeStack.functionNode)
+          if (!setupFunctionData || !setupFunctionData.afterAwait) {
+            return
+          }
+
+          if (watchCallNodes.has(node) && !isMaybeUsedStopHandle(node)) {
+            addForbiddenNode(setupFunctionData.setupProperty, node)
+          }
+        },
+        ':function:exit' (node) {
+          scopeStack = scopeStack.upper
+
+          setupFunctions.delete(node)
+        }
+      },
+      utils.executeOnVue(context, obj => {
+        const reportsList = obj.properties
+          .map(item => forbiddenNodes.get(item))
+          .filter(reports => !!reports)
+        for (const reports of reportsList) {
+          for (const node of reports) {
+            context.report({
+              node,
+              messageId: 'forbidden'
+            })
+          }
+        }
+      })
+    )
+  }
+}