eslint/lib/rules/no-dupe-args.js

   1 /**
   2  * @fileoverview Rule to flag duplicate arguments
   3  * @author Jamund Ferguson
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Rule Definition
  10 //------------------------------------------------------------------------------
  11
  12 /** @type {import('../shared/types').Rule} */
  13 module.exports = {
  14     meta: {
  15         type: "problem",
  16
  17         docs: {
  18             description: "Disallow duplicate arguments in `function` definitions",
  19             recommended: true,
  20             url: "https://eslint.org/docs/latest/rules/no-dupe-args"
  21         },
  22
  23         schema: [],
  24
  25         messages: {
  26             unexpected: "Duplicate param '{{name}}'."
  27         }
  28     },
  29
  30     create(context) {
  31
  32         const sourceCode = context.sourceCode;
  33
  34         //--------------------------------------------------------------------------
  35         // Helpers
  36         //--------------------------------------------------------------------------
  37
  38         /**
  39          * Checks whether or not a given definition is a parameter's.
  40          * @param {eslint-scope.DefEntry} def A definition to check.
  41          * @returns {boolean} `true` if the definition is a parameter's.
  42          */
  43         function isParameter(def) {
  44             return def.type === "Parameter";
  45         }
  46
  47         /**
  48          * Determines if a given node has duplicate parameters.
  49          * @param {ASTNode} node The node to check.
  50          * @returns {void}
  51          * @private
  52          */
  53         function checkParams(node) {
  54             const variables = sourceCode.getDeclaredVariables(node);
  55
  56             for (let i = 0; i < variables.length; ++i) {
  57                 const variable = variables[i];
  58
  59                 // Checks and reports duplications.
  60                 const defs = variable.defs.filter(isParameter);
  61
  62                 if (defs.length >= 2) {
  63                     context.report({
  64                         node,
  65                         messageId: "unexpected",
  66                         data: { name: variable.name }
  67                     });
  68                 }
  69             }
  70         }
  71
  72         //--------------------------------------------------------------------------
  73         // Public API
  74         //--------------------------------------------------------------------------
  75
  76         return {
  77             FunctionDeclaration: checkParams,
  78             FunctionExpression: checkParams
  79         };
  80
  81     }
  82 };