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