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