eslint/lib/rules/no-labels.js

   1 /**
   2  * @fileoverview Disallow Labeled Statements
   3  * @author Nicholas C. Zakas
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Requirements
   9 //------------------------------------------------------------------------------
  10
  11 const astUtils = require("./utils/ast-utils");
  12
  13 //------------------------------------------------------------------------------
  14 // Rule Definition
  15 //------------------------------------------------------------------------------
  16
  17 /** @type {import('../shared/types').Rule} */
  18 module.exports = {
  19     meta: {
  20         type: "suggestion",
  21
  22         docs: {
  23             description: "Disallow labeled statements",
  24             recommended: false,
  25             url: "https://eslint.org/docs/rules/no-labels"
  26         },
  27
  28         schema: [
  29             {
  30                 type: "object",
  31                 properties: {
  32                     allowLoop: {
  33                         type: "boolean",
  34                         default: false
  35                     },
  36                     allowSwitch: {
  37                         type: "boolean",
  38                         default: false
  39                     }
  40                 },
  41                 additionalProperties: false
  42             }
  43         ],
  44
  45         messages: {
  46             unexpectedLabel: "Unexpected labeled statement.",
  47             unexpectedLabelInBreak: "Unexpected label in break statement.",
  48             unexpectedLabelInContinue: "Unexpected label in continue statement."
  49         }
  50     },
  51
  52     create(context) {
  53         const options = context.options[0];
  54         const allowLoop = options && options.allowLoop;
  55         const allowSwitch = options && options.allowSwitch;
  56         let scopeInfo = null;
  57
  58         /**
  59          * Gets the kind of a given node.
  60          * @param {ASTNode} node A node to get.
  61          * @returns {string} The kind of the node.
  62          */
  63         function getBodyKind(node) {
  64             if (astUtils.isLoop(node)) {
  65                 return "loop";
  66             }
  67             if (node.type === "SwitchStatement") {
  68                 return "switch";
  69             }
  70             return "other";
  71         }
  72
  73         /**
  74          * Checks whether the label of a given kind is allowed or not.
  75          * @param {string} kind A kind to check.
  76          * @returns {boolean} `true` if the kind is allowed.
  77          */
  78         function isAllowed(kind) {
  79             switch (kind) {
  80                 case "loop": return allowLoop;
  81                 case "switch": return allowSwitch;
  82                 default: return false;
  83             }
  84         }
  85
  86         /**
  87          * Checks whether a given name is a label of a loop or not.
  88          * @param {string} label A name of a label to check.
  89          * @returns {boolean} `true` if the name is a label of a loop.
  90          */
  91         function getKind(label) {
  92             let info = scopeInfo;
  93
  94             while (info) {
  95                 if (info.label === label) {
  96                     return info.kind;
  97                 }
  98                 info = info.upper;
  99             }
 100
 101             /* c8 ignore next */
 102             return "other";
 103         }
 104
 105         //--------------------------------------------------------------------------
 106         // Public
 107         //--------------------------------------------------------------------------
 108
 109         return {
 110             LabeledStatement(node) {
 111                 scopeInfo = {
 112                     label: node.label.name,
 113                     kind: getBodyKind(node.body),
 114                     upper: scopeInfo
 115                 };
 116             },
 117
 118             "LabeledStatement:exit"(node) {
 119                 if (!isAllowed(scopeInfo.kind)) {
 120                     context.report({
 121                         node,
 122                         messageId: "unexpectedLabel"
 123                     });
 124                 }
 125
 126                 scopeInfo = scopeInfo.upper;
 127             },
 128
 129             BreakStatement(node) {
 130                 if (node.label && !isAllowed(getKind(node.label.name))) {
 131                     context.report({
 132                         node,
 133                         messageId: "unexpectedLabelInBreak"
 134                     });
 135                 }
 136             },
 137
 138             ContinueStatement(node) {
 139                 if (node.label && !isAllowed(getKind(node.label.name))) {
 140                     context.report({
 141                         node,
 142                         messageId: "unexpectedLabelInContinue"
 143                     });
 144                 }
 145             }
 146         };
 147
 148     }
 149 };