eslint/lib/rules/new-parens.js

   1 /**
   2  * @fileoverview Rule to flag when using constructor without parentheses
   3  * @author Ilya Volodin
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const astUtils = require("./utils/ast-utils");
  13
  14 //------------------------------------------------------------------------------
  15 // Helpers
  16 //------------------------------------------------------------------------------
  17
  18 //------------------------------------------------------------------------------
  19 // Rule Definition
  20 //------------------------------------------------------------------------------
  21
  22 /** @type {import('../shared/types').Rule} */
  23 module.exports = {
  24     meta: {
  25         type: "layout",
  26
  27         docs: {
  28             description: "Enforce or disallow parentheses when invoking a constructor with no arguments",
  29             recommended: false,
  30             url: "https://eslint.org/docs/latest/rules/new-parens"
  31         },
  32
  33         fixable: "code",
  34         schema: [
  35             {
  36                 enum: ["always", "never"]
  37             }
  38         ],
  39         messages: {
  40             missing: "Missing '()' invoking a constructor.",
  41             unnecessary: "Unnecessary '()' invoking a constructor with no arguments."
  42         }
  43     },
  44
  45     create(context) {
  46         const options = context.options;
  47         const always = options[0] !== "never"; // Default is always
  48
  49         const sourceCode = context.sourceCode;
  50
  51         return {
  52             NewExpression(node) {
  53                 if (node.arguments.length !== 0) {
  54                     return; // if there are arguments, there have to be parens
  55                 }
  56
  57                 const lastToken = sourceCode.getLastToken(node);
  58                 const hasLastParen = lastToken && astUtils.isClosingParenToken(lastToken);
  59
  60                 // `hasParens` is true only if the new expression ends with its own parens, e.g., new new foo() does not end with its own parens
  61                 const hasParens = hasLastParen &&
  62                     astUtils.isOpeningParenToken(sourceCode.getTokenBefore(lastToken)) &&
  63                     node.callee.range[1] < node.range[1];
  64
  65                 if (always) {
  66                     if (!hasParens) {
  67                         context.report({
  68                             node,
  69                             messageId: "missing",
  70                             fix: fixer => fixer.insertTextAfter(node, "()")
  71                         });
  72                     }
  73                 } else {
  74                     if (hasParens) {
  75                         context.report({
  76                             node,
  77                             messageId: "unnecessary",
  78                             fix: fixer => [
  79                                 fixer.remove(sourceCode.getTokenBefore(lastToken)),
  80                                 fixer.remove(lastToken),
  81                                 fixer.insertTextBefore(node, "("),
  82                                 fixer.insertTextAfter(node, ")")
  83                             ]
  84                         });
  85                     }
  86                 }
  87             }
  88         };
  89     }
  90 };