eslint/lib/rules/multiline-ternary.js

   1 /**
   2  * @fileoverview Enforce newlines between operands of ternary expressions
   3  * @author Kai Cataldo
   4  */
   5
   6 "use strict";
   7
   8 const astUtils = require("./utils/ast-utils");
   9
  10 //------------------------------------------------------------------------------
  11 // Rule Definition
  12 //------------------------------------------------------------------------------
  13
  14 module.exports = {
  15     meta: {
  16         type: "layout",
  17
  18         docs: {
  19             description: "enforce newlines between operands of ternary expressions",
  20             category: "Stylistic Issues",
  21             recommended: false,
  22             url: "https://eslint.org/docs/rules/multiline-ternary"
  23         },
  24
  25         schema: [
  26             {
  27                 enum: ["always", "always-multiline", "never"]
  28             }
  29         ],
  30         messages: {
  31             expectedTestCons: "Expected newline between test and consequent of ternary expression.",
  32             expectedConsAlt: "Expected newline between consequent and alternate of ternary expression.",
  33             unexpectedTestCons: "Unexpected newline between test and consequent of ternary expression.",
  34             unexpectedConsAlt: "Unexpected newline between consequent and alternate of ternary expression."
  35         }
  36     },
  37
  38     create(context) {
  39         const option = context.options[0];
  40         const multiline = option !== "never";
  41         const allowSingleLine = option === "always-multiline";
  42
  43         //--------------------------------------------------------------------------
  44         // Helpers
  45         //--------------------------------------------------------------------------
  46
  47         /**
  48          * Tests whether node is preceded by supplied tokens
  49          * @param {ASTNode} node node to check
  50          * @param {ASTNode} parentNode parent of node to report
  51          * @param {boolean} expected whether newline was expected or not
  52          * @returns {void}
  53          * @private
  54          */
  55         function reportError(node, parentNode, expected) {
  56             context.report({
  57                 node,
  58                 messageId: `${expected ? "expected" : "unexpected"}${node === parentNode.test ? "TestCons" : "ConsAlt"}`
  59             });
  60         }
  61
  62         //--------------------------------------------------------------------------
  63         // Public
  64         //--------------------------------------------------------------------------
  65
  66         return {
  67             ConditionalExpression(node) {
  68                 const areTestAndConsequentOnSameLine = astUtils.isTokenOnSameLine(node.test, node.consequent);
  69                 const areConsequentAndAlternateOnSameLine = astUtils.isTokenOnSameLine(node.consequent, node.alternate);
  70
  71                 if (!multiline) {
  72                     if (!areTestAndConsequentOnSameLine) {
  73                         reportError(node.test, node, false);
  74                     }
  75
  76                     if (!areConsequentAndAlternateOnSameLine) {
  77                         reportError(node.consequent, node, false);
  78                     }
  79                 } else {
  80                     if (allowSingleLine && node.loc.start.line === node.loc.end.line) {
  81                         return;
  82                     }
  83
  84                     if (areTestAndConsequentOnSameLine) {
  85                         reportError(node.test, node, true);
  86                     }
  87
  88                     if (areConsequentAndAlternateOnSameLine) {
  89                         reportError(node.consequent, node, true);
  90                     }
  91                 }
  92             }
  93         };
  94     }
  95 };