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 module.exports = {
  23     meta: {
  24         type: "layout",
  25
  26         docs: {
  27             description: "enforce or disallow parentheses when invoking a constructor with no arguments",
  28             recommended: false,
  29             url: "https://eslint.org/docs/rules/new-parens"
  30         },
  31
  32         fixable: "code",
  33         schema: {
  34             anyOf: [
  35                 {
  36                     type: "array",
  37                     items: [
  38                         {
  39                             enum: ["always", "never"]
  40                         }
  41                     ],
  42                     minItems: 0,
  43                     maxItems: 1
  44                 }
  45             ]
  46         },
  47         messages: {
  48             missing: "Missing '()' invoking a constructor.",
  49             unnecessary: "Unnecessary '()' invoking a constructor with no arguments."
  50         }
  51     },
  52
  53     create(context) {
  54         const options = context.options;
  55         const always = options[0] !== "never"; // Default is always
  56
  57         const sourceCode = context.getSourceCode();
  58
  59         return {
  60             NewExpression(node) {
  61                 if (node.arguments.length !== 0) {
  62                     return; // if there are arguments, there have to be parens
  63                 }
  64
  65                 const lastToken = sourceCode.getLastToken(node);
  66                 const hasLastParen = lastToken && astUtils.isClosingParenToken(lastToken);
  67
  68                 // `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
  69                 const hasParens = hasLastParen &&
  70                     astUtils.isOpeningParenToken(sourceCode.getTokenBefore(lastToken)) &&
  71                     node.callee.range[1] < node.range[1];
  72
  73                 if (always) {
  74                     if (!hasParens) {
  75                         context.report({
  76                             node,
  77                             messageId: "missing",
  78                             fix: fixer => fixer.insertTextAfter(node, "()")
  79                         });
  80                     }
  81                 } else {
  82                     if (hasParens) {
  83                         context.report({
  84                             node,
  85                             messageId: "unnecessary",
  86                             fix: fixer => [
  87                                 fixer.remove(sourceCode.getTokenBefore(lastToken)),
  88                                 fixer.remove(lastToken),
  89                                 fixer.insertTextBefore(node, "("),
  90                                 fixer.insertTextAfter(node, ")")
  91                             ]
  92                         });
  93                     }
  94                 }
  95             }
  96         };
  97     }
  98 };