eslint/lib/rules/no-dupe-class-members.js

   1 /**
   2  * @fileoverview A rule to disallow duplicate name in class members.
   3  * @author Toru Nagashima
   4  */
   5
   6 "use strict";
   7
   8 const astUtils = require("./utils/ast-utils");
   9
  10 //------------------------------------------------------------------------------
  11 // Rule Definition
  12 //------------------------------------------------------------------------------
  13
  14 /** @type {import('../shared/types').Rule} */
  15 module.exports = {
  16     meta: {
  17         type: "problem",
  18
  19         docs: {
  20             description: "disallow duplicate class members",
  21             recommended: true,
  22             url: "https://eslint.org/docs/rules/no-dupe-class-members"
  23         },
  24
  25         schema: [],
  26
  27         messages: {
  28             unexpected: "Duplicate name '{{name}}'."
  29         }
  30     },
  31
  32     create(context) {
  33         let stack = [];
  34
  35         /**
  36          * Gets state of a given member name.
  37          * @param {string} name A name of a member.
  38          * @param {boolean} isStatic A flag which specifies that is a static member.
  39          * @returns {Object} A state of a given member name.
  40          *   - retv.init {boolean} A flag which shows the name is declared as normal member.
  41          *   - retv.get {boolean} A flag which shows the name is declared as getter.
  42          *   - retv.set {boolean} A flag which shows the name is declared as setter.
  43          */
  44         function getState(name, isStatic) {
  45             const stateMap = stack[stack.length - 1];
  46             const key = `$${name}`; // to avoid "__proto__".
  47
  48             if (!stateMap[key]) {
  49                 stateMap[key] = {
  50                     nonStatic: { init: false, get: false, set: false },
  51                     static: { init: false, get: false, set: false }
  52                 };
  53             }
  54
  55             return stateMap[key][isStatic ? "static" : "nonStatic"];
  56         }
  57
  58         return {
  59
  60             // Initializes the stack of state of member declarations.
  61             Program() {
  62                 stack = [];
  63             },
  64
  65             // Initializes state of member declarations for the class.
  66             ClassBody() {
  67                 stack.push(Object.create(null));
  68             },
  69
  70             // Disposes the state for the class.
  71             "ClassBody:exit"() {
  72                 stack.pop();
  73             },
  74
  75             // Reports the node if its name has been declared already.
  76             "MethodDefinition, PropertyDefinition"(node) {
  77                 const name = astUtils.getStaticPropertyName(node);
  78                 const kind = node.type === "MethodDefinition" ? node.kind : "field";
  79
  80                 if (name === null || kind === "constructor") {
  81                     return;
  82                 }
  83
  84                 const state = getState(name, node.static);
  85                 let isDuplicate = false;
  86
  87                 if (kind === "get") {
  88                     isDuplicate = (state.init || state.get);
  89                     state.get = true;
  90                 } else if (kind === "set") {
  91                     isDuplicate = (state.init || state.set);
  92                     state.set = true;
  93                 } else {
  94                     isDuplicate = (state.init || state.get || state.set);
  95                     state.init = true;
  96                 }
  97
  98                 if (isDuplicate) {
  99                     context.report({ node, messageId: "unexpected", data: { name } });
 100                 }
 101             }
 102         };
 103     }
 104 };