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

Author: ota-meshi

docs/rules/README.md

@@ -164,6 +164,7 @@ For example:
 | [vue/no-restricted-syntax](./no-restricted-syntax.md) | disallow specified syntax |  |
 | [vue/no-static-inline-styles](./no-static-inline-styles.md) | disallow static inline `style` attributes |  |
 | [vue/no-unsupported-features](./no-unsupported-features.md) | disallow unsupported Vue.js syntax on the specified version | :wrench: |
+| [vue/no-watch-after-await](./no-watch-after-await.md) | disallow asynchronously registered `watch` |  |
 | [vue/object-curly-spacing](./object-curly-spacing.md) | enforce consistent spacing inside braces | :wrench: |
 | [vue/padding-line-between-blocks](./padding-line-between-blocks.md) | require or disallow padding lines between blocks | :wrench: |
 | [vue/require-direct-export](./require-direct-export.md) | require the component to be directly exported |  |

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

@@ -0,0 +1,47 @@
+---
+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`
+
+## :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(() => { /* ... */ })
+
+    await doSomething()
+
+    /* ✗ BAD */
+    watch(() => { /* ... */ })
+  }
+}
+</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)
+
+## :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/index.js

@@ -63,6 +63,7 @@ module.exports = {
     'no-unused-vars': require('./rules/no-unused-vars'),
     '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-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 +1,107 @@
+/**
+ * @author Yosuke Ota
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+const { ReferenceTracker } = require('eslint-utils')
+const utils = require('../utils')
+
+module.exports = {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description: 'disallow asynchronously registered `watch`',
+      category: undefined,
+      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
+              }
+            }
+          }
+
+          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)) {
+            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'
+            })
+          }
+        }
+      })
+    )
+  }
+}

package.json

@@ -8,6 +8,7 @@
     "test:base": "mocha \"tests/lib/**/*.js\" --reporter dot",
     "test": "nyc npm run test:base -- \"tests/integrations/*.js\" --timeout 60000",
     "debug": "mocha --inspect-brk \"tests/lib/**/*.js\" --reporter dot --timeout 60000",
+    "cover:report": "nyc report --reporter=html",
     "lint": "eslint . --rulesdir eslint-internal-rules",
     "pretest": "npm run lint",
     "preversion": "npm test && npm run update && git add .",
@@ -47,9 +48,10 @@
     "eslint": "^5.0.0 || ^6.0.0"
   },
   "dependencies": {
+    "eslint-utils": "^2.0.0",
     "natural-compare": "^1.4.0",
-    "vue-eslint-parser": "^7.0.0",
-    "semver": "^5.6.0"
+    "semver": "^5.6.0",
+    "vue-eslint-parser": "^7.0.0"
   },
   "devDependencies": {
     "@types/node": "^4.2.16",

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

@@ -0,0 +1,115 @@
+/**
+ * @author Yosuke Ota
+ */
+'use strict'
+
+const RuleTester = require('eslint').RuleTester
+const rule = require('../../../lib/rules/no-watch-after-await')
+
+const tester = new RuleTester({
+  parser: require.resolve('vue-eslint-parser'),
+  parserOptions: { ecmaVersion: 2019, sourceType: 'module' }
+})
+
+tester.run('no-watch-after-await', rule, {
+  valid: [
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      import {watch} from 'vue'
+      export default {
+        async setup() {
+          watch(() => { /* ... */ }) // ok
+
+          await doSomething()
+        }
+      }
+      </script>
+      `
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      import {watch} from 'vue'
+      export default {
+        async setup() {
+          watch(() => { /* ... */ })
+        }
+      }
+      </script>
+      `
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      import {onMounted} from 'vue'
+      export default {
+        async _setup() {
+          await doSomething()
+
+          onMounted(() => { /* ... */ }) // error
+        }
+      }
+      </script>
+      `
+    }
+  ],
+  invalid: [
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      import {watch} from 'vue'
+      export default {
+        async setup() {
+          await doSomething()
+
+          watch(() => { /* ... */ }) // error
+        }
+      }
+      </script>
+      `,
+      errors: [
+        {
+          message: 'The `watch` after `await` expression are forbidden.',
+          line: 8,
+          column: 11,
+          endLine: 8,
+          endColumn: 37
+        }
+      ]
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      import {watch} from 'vue'
+      export default {
+        async setup() {
+          await doSomething()
+
+          watch(() => { /* ... */ })
+
+          await doSomething()
+
+          watch(() => { /* ... */ })
+        }
+      }
+      </script>
+      `,
+      errors: [
+        {
+          messageId: 'forbidden',
+          line: 8
+        },
+        {
+          messageId: 'forbidden',
+          line: 12
+        }
+      ]
+    }
+  ]
+})