.config/coc/extensions/node_modules/coc-prettier/node_modules/eslint/lib/rules/no-fallthrough.js

   1 /**
   2  * @fileoverview Rule to flag fall-through cases in switch statements.
   3  * @author Matt DuVall <http://mattduvall.com/>
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Requirements
   9 //------------------------------------------------------------------------------
  10
  11 const lodash = require("lodash");
  12
  13 //------------------------------------------------------------------------------
  14 // Helpers
  15 //------------------------------------------------------------------------------
  16
  17 const DEFAULT_FALLTHROUGH_COMMENT = /falls?\s?through/iu;
  18
  19 /**
  20  * Checks whether or not a given node has a fallthrough comment.
  21  * @param {ASTNode} node A SwitchCase node to get comments.
  22  * @param {RuleContext} context A rule context which stores comments.
  23  * @param {RegExp} fallthroughCommentPattern A pattern to match comment to.
  24  * @returns {boolean} `true` if the node has a valid fallthrough comment.
  25  */
  26 function hasFallthroughComment(node, context, fallthroughCommentPattern) {
  27     const sourceCode = context.getSourceCode();
  28     const comment = lodash.last(sourceCode.getCommentsBefore(node));
  29
  30     return Boolean(comment && fallthroughCommentPattern.test(comment.value));
  31 }
  32
  33 /**
  34  * Checks whether or not a given code path segment is reachable.
  35  * @param {CodePathSegment} segment A CodePathSegment to check.
  36  * @returns {boolean} `true` if the segment is reachable.
  37  */
  38 function isReachable(segment) {
  39     return segment.reachable;
  40 }
  41
  42 /**
  43  * Checks whether a node and a token are separated by blank lines
  44  * @param {ASTNode} node The node to check
  45  * @param {Token} token The token to compare against
  46  * @returns {boolean} `true` if there are blank lines between node and token
  47  */
  48 function hasBlankLinesBetween(node, token) {
  49     return token.loc.start.line > node.loc.end.line + 1;
  50 }
  51
  52 //------------------------------------------------------------------------------
  53 // Rule Definition
  54 //------------------------------------------------------------------------------
  55
  56 module.exports = {
  57     meta: {
  58         type: "problem",
  59
  60         docs: {
  61             description: "disallow fallthrough of `case` statements",
  62             category: "Best Practices",
  63             recommended: true,
  64             url: "https://eslint.org/docs/rules/no-fallthrough"
  65         },
  66
  67         schema: [
  68             {
  69                 type: "object",
  70                 properties: {
  71                     commentPattern: {
  72                         type: "string",
  73                         default: ""
  74                     }
  75                 },
  76                 additionalProperties: false
  77             }
  78         ],
  79         messages: {
  80             case: "Expected a 'break' statement before 'case'.",
  81             default: "Expected a 'break' statement before 'default'."
  82         }
  83     },
  84
  85     create(context) {
  86         const options = context.options[0] || {};
  87         let currentCodePath = null;
  88         const sourceCode = context.getSourceCode();
  89
  90         /*
  91          * We need to use leading comments of the next SwitchCase node because
  92          * trailing comments is wrong if semicolons are omitted.
  93          */
  94         let fallthroughCase = null;
  95         let fallthroughCommentPattern = null;
  96
  97         if (options.commentPattern) {
  98             fallthroughCommentPattern = new RegExp(options.commentPattern, "u");
  99         } else {
 100             fallthroughCommentPattern = DEFAULT_FALLTHROUGH_COMMENT;
 101         }
 102
 103         return {
 104             onCodePathStart(codePath) {
 105                 currentCodePath = codePath;
 106             },
 107             onCodePathEnd() {
 108                 currentCodePath = currentCodePath.upper;
 109             },
 110
 111             SwitchCase(node) {
 112
 113                 /*
 114                  * Checks whether or not there is a fallthrough comment.
 115                  * And reports the previous fallthrough node if that does not exist.
 116                  */
 117                 if (fallthroughCase && !hasFallthroughComment(node, context, fallthroughCommentPattern)) {
 118                     context.report({
 119                         messageId: node.test ? "case" : "default",
 120                         node
 121                     });
 122                 }
 123                 fallthroughCase = null;
 124             },
 125
 126             "SwitchCase:exit"(node) {
 127                 const nextToken = sourceCode.getTokenAfter(node);
 128
 129                 /*
 130                  * `reachable` meant fall through because statements preceded by
 131                  * `break`, `return`, or `throw` are unreachable.
 132                  * And allows empty cases and the last case.
 133                  */
 134                 if (currentCodePath.currentSegments.some(isReachable) &&
 135                     (node.consequent.length > 0 || hasBlankLinesBetween(node, nextToken)) &&
 136                     lodash.last(node.parent.cases) !== node) {
 137                     fallthroughCase = node;
 138                 }
 139             }
 140         };
 141     }
 142 };