Add vue/no-computed-properties-in-data rule

docs/rules/README.md

@@ -300,6 +300,7 @@ For example:
 | [vue/next-tick-style](./next-tick-style.md) | enforce Promise or callback style in `nextTick` | :wrench: |
 | [vue/no-bare-strings-in-template](./no-bare-strings-in-template.md) | disallow the use of bare strings in `<template>` |  |
 | [vue/no-boolean-default](./no-boolean-default.md) | disallow boolean defaults | :wrench: |
+| [vue/no-computed-properties-in-data](./no-computed-properties-in-data.md) | disallow accessing computed properties in `data`. |  |
 | [vue/no-deprecated-v-is](./no-deprecated-v-is.md) | disallow deprecated `v-is` directive (in Vue.js 3.1.0+) | :wrench: |
 | [vue/no-duplicate-attr-inheritance](./no-duplicate-attr-inheritance.md) | enforce `inheritAttrs` to be set to `false` when using `v-bind="$attrs"` |  |
 | [vue/no-empty-component-block](./no-empty-component-block.md) | disallow the `<template>` `<script>` `<style>` block to be empty |  |

docs/rules/no-computed-properties-in-data.md

@@ -0,0 +1,45 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/no-computed-properties-in-data
+description: disallow accessing computed properties in `data`.
+---
+# vue/no-computed-properties-in-data
+
+> disallow accessing computed properties in `data`.
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+
+## :book: Rule Details
+
+This rule disallow accessing computed properties in `data()`.  
+The computed property cannot be accessed in `data()` because is before initialization.
+
+<eslint-code-block :rules="{'vue/no-computed-properties-in-data': ['error']}">
+
+```vue
+<script>
+export default {
+  data() {
+    return  {
+      /* ✗ BAD */
+      bar: this.foo
+    }
+  },
+  computed: {
+    foo () {}
+  }
+}
+</script>
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/no-computed-properties-in-data.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/no-computed-properties-in-data.js)

lib/index.js

@@ -56,6 +56,7 @@ module.exports = {
     'no-async-in-computed-properties': require('./rules/no-async-in-computed-properties'),
     'no-bare-strings-in-template': require('./rules/no-bare-strings-in-template'),
     'no-boolean-default': require('./rules/no-boolean-default'),
+    'no-computed-properties-in-data': require('./rules/no-computed-properties-in-data'),
     'no-confusing-v-for-v-if': require('./rules/no-confusing-v-for-v-if'),
     'no-constant-condition': require('./rules/no-constant-condition'),
     'no-custom-modifiers-on-v-model': require('./rules/no-custom-modifiers-on-v-model'),

lib/rules/no-computed-properties-in-data.js

@@ -0,0 +1,108 @@
+/**
+ * @author  Yosuke Ota
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const utils = require('../utils')
+
+/**
+ * @typedef {import('../utils').VueObjectData} VueObjectData
+ */
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow accessing computed properties in `data`.',
+      categories: undefined,
+      url: 'https://eslint.vuejs.org/rules/no-computed-properties-in-data.html'
+    },
+    fixable: null,
+    schema: [],
+    messages: {
+      cannotBeUsed:
+        'The computed property cannot be used in `data()` because it is before initialization.'
+    }
+  },
+  /** @param {RuleContext} context */
+  create(context) {
+    /** @type {Map<ObjectExpression, {data: FunctionExpression | ArrowFunctionExpression, computedNames:Set<string>}>} */
+    const contextMap = new Map()
+
+    /**
+     * @typedef {object} ScopeStack
+     * @property {ScopeStack | null} upper
+     * @property {FunctionExpression | FunctionDeclaration | ArrowFunctionExpression} node
+     */
+    /** @type {ScopeStack | null} */
+    let scopeStack = null
+
+    return utils.compositingVisitors(
+      {
+        /**
+         * @param {FunctionExpression | FunctionDeclaration | ArrowFunctionExpression} node
+         */
+        ':function'(node) {
+          scopeStack = {
+            upper: scopeStack,
+            node
+          }
+        },
+        ':function:exit'() {
+          scopeStack = scopeStack && scopeStack.upper
+        }
+      },
+      utils.defineVueVisitor(context, {
+        onVueObjectEnter(node) {
+          const dataProperty = utils.findProperty(node, 'data')
+          if (
+            !dataProperty ||
+            (dataProperty.value.type !== 'FunctionExpression' &&
+              dataProperty.value.type !== 'ArrowFunctionExpression')
+          ) {
+            return
+          }
+          const computedNames = new Set()
+          for (const computed of utils.iterateProperties(
+            node,
+            new Set(['computed'])
+          )) {
+            computedNames.add(computed.name)
+          }
+
+          contextMap.set(node, { data: dataProperty.value, computedNames })
+        },
+        /**
+         * @param {MemberExpression} node
+         * @param {VueObjectData} vueData
+         */
+        MemberExpression(node, vueData) {
+          if (!scopeStack || !utils.isThis(node.object, context)) {
+            return
+          }
+          const ctx = contextMap.get(vueData.node)
+          if (!ctx || ctx.data !== scopeStack.node) {
+            return
+          }
+          const name = utils.getStaticPropertyName(node)
+          if (!name || !ctx.computedNames.has(name)) {
+            return
+          }
+          context.report({
+            node,
+            messageId: 'cannotBeUsed'
+          })
+        }
+      })
+    )
+  }
+}

tests/lib/rules/no-computed-properties-in-data.js

@@ -0,0 +1,130 @@
+/**
+ * @author  Yosuke Ota
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+const RuleTester = require('eslint').RuleTester
+const rule = require('../../../lib/rules/no-computed-properties-in-data')
+
+const tester = new RuleTester({
+  parser: require.resolve('vue-eslint-parser'),
+  parserOptions: {
+    ecmaVersion: 2020,
+    sourceType: 'module'
+  }
+})
+
+tester.run('no-computed-properties-in-data', rule, {
+  valid: [
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      export default {
+        data() {
+          const foo = this.foo
+          return {}
+        }
+      }
+      </script>
+      `
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      export default {
+        data() {
+          const foo = this.foo()
+          return {}
+        },
+        methods: {
+          foo() {}
+        }
+      }
+      </script>
+      `
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      export default {
+        props: ['foo'],
+        data() {
+          const foo = this.foo
+          return {}
+        },
+      }
+      </script>
+      `
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      export default {
+        data: {
+          foo: this.foo
+        },
+        computed: {
+          foo () {}
+        }
+      }
+      </script>
+      `
+    }
+  ],
+  invalid: [
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      export default {
+        data() {
+          const foo = this.foo
+          return  {}
+        },
+        computed: {
+          foo () {}
+        }
+      }
+      </script>
+      `,
+      errors: [
+        {
+          message:
+            'The computed property cannot be used in `data()` because it is before initialization.',
+          line: 5,
+          column: 23
+        }
+      ]
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+      export default {
+        data() {
+          const vm = this
+          const foo = vm.foo
+          return  {}
+        },
+        computed: {
+          foo () {}
+        }
+      }
+      </script>
+      `,
+      errors: [
+        {
+          message:
+            'The computed property cannot be used in `data()` because it is before initialization.',
+          line: 6,
+          column: 23
+        }
+      ]
+    }
+  ]
+})

tools/new-rule.js

@@ -32,7 +32,7 @@ const logger = console
 // Requirements
 // ------------------------------------------------------------------------------
 
-// ...
+const utils = require('../utils')
 
 // ------------------------------------------------------------------------------
 // Helpers