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 module.exports = {
  29     meta: {
  30         type: "suggestion",
  31
  32         docs: {
  33             description: "disallow arrow functions where they could be confused with comparisons",
  34             recommended: false,
  35             url: "https://eslint.org/docs/rules/no-confusing-arrow"
  36         },
  37
  38         fixable: "code",
  39
  40         schema: [{
  41             type: "object",
  42             properties: {
  43                 allowParens: { type: "boolean", default: true }
  44             },
  45             additionalProperties: false
  46         }],
  47
  48         messages: {
  49             confusing: "Arrow function used ambiguously with a conditional expression."
  50         }
  51     },
  52
  53     create(context) {
  54         const config = context.options[0] || {};
  55         const allowParens = config.allowParens || (config.allowParens === void 0);
  56         const sourceCode = context.getSourceCode();
  57
  58
  59         /**
  60          * Reports if an arrow function contains an ambiguous conditional.
  61          * @param {ASTNode} node A node to check and report.
  62          * @returns {void}
  63          */
  64         function checkArrowFunc(node) {
  65             const body = node.body;
  66
  67             if (isConditional(body) && !(allowParens && astUtils.isParenthesised(sourceCode, body))) {
  68                 context.report({
  69                     node,
  70                     messageId: "confusing",
  71                     fix(fixer) {
  72
  73                         // if `allowParens` is not set to true don't bother wrapping in parens
  74                         return allowParens && fixer.replaceText(node.body, `(${sourceCode.getText(node.body)})`);
  75                     }
  76                 });
  77             }
  78         }
  79
  80         return {
  81             ArrowFunctionExpression: checkArrowFunc
  82         };
  83     }
  84 };