eslint/lib/rules/no-confusing-arrow.js

   1 /**
   2  * @fileoverview A rule to warn against using arrow functions when they could be
   3  * confused with comparisons
   4  * @author Jxck <https://github.com/Jxck>
   5  */
   6
   7 "use strict";
   8
   9 const astUtils = require("./utils/ast-utils.js");
  10
  11 //------------------------------------------------------------------------------
  12 // Helpers
  13 //------------------------------------------------------------------------------
  14
  15 /**
  16  * Checks whether or not a node is a conditional expression.
  17  * @param {ASTNode} node node to test
  18  * @returns {boolean} `true` if the node is a conditional expression.
  19  */
  20 function isConditional(node) {
  21     return node && node.type === "ConditionalExpression";
  22 }
  23
  24 //------------------------------------------------------------------------------
  25 // Rule Definition
  26 //------------------------------------------------------------------------------
  27
  28 /** @type {import('../shared/types').Rule} */
  29 module.exports = {
  30     meta: {
  31         type: "suggestion",
  32
  33         docs: {
  34             description: "Disallow arrow functions where they could be confused with comparisons",
  35             recommended: false,
  36             url: "https://eslint.org/docs/rules/no-confusing-arrow"
  37         },
  38
  39         fixable: "code",
  40
  41         schema: [{
  42             type: "object",
  43             properties: {
  44                 allowParens: { type: "boolean", default: true },
  45                 onlyOneSimpleParam: { type: "boolean", default: false }
  46             },
  47             additionalProperties: false
  48         }],
  49
  50         messages: {
  51             confusing: "Arrow function used ambiguously with a conditional expression."
  52         }
  53     },
  54
  55     create(context) {
  56         const config = context.options[0] || {};
  57         const allowParens = config.allowParens || (config.allowParens === void 0);
  58         const onlyOneSimpleParam = config.onlyOneSimpleParam;
  59         const sourceCode = context.getSourceCode();
  60
  61
  62         /**
  63          * Reports if an arrow function contains an ambiguous conditional.
  64          * @param {ASTNode} node A node to check and report.
  65          * @returns {void}
  66          */
  67         function checkArrowFunc(node) {
  68             const body = node.body;
  69
  70             if (isConditional(body) &&
  71                 !(allowParens && astUtils.isParenthesised(sourceCode, body)) &&
  72                 !(onlyOneSimpleParam && !(node.params.length === 1 && node.params[0].type === "Identifier"))) {
  73                 context.report({
  74                     node,
  75                     messageId: "confusing",
  76                     fix(fixer) {
  77
  78                         // if `allowParens` is not set to true don't bother wrapping in parens
  79                         return allowParens && fixer.replaceText(node.body, `(${sourceCode.getText(node.body)})`);
  80                     }
  81                 });
  82             }
  83         }
  84
  85         return {
  86             ArrowFunctionExpression: checkArrowFunc
  87         };
  88     }
  89 };