2/node_modules/eslint-plugin-vue/lib/rules/no-computed-properties-in-data.js

/**
 * @author  Yosuke Ota
 * See LICENSE file in root directory for full license.
 */
'use strict'

const utils = require('../utils')

/**
 * @typedef {import('../utils').VueObjectData} VueObjectData
 */

module.exports = {
  meta: {
    type: 'problem',
    docs: {
      description: 'disallow accessing computed properties in `data`',
      categories: ['vue3-essential', 'vue2-essential'],
      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'
          })
        }
      })
    )
  }
}