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