1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
/**
* @fileoverview Rule to flag fall-through cases in switch statements.
* @author Matt DuVall <http://mattduvall.com/>
*/
"use strict";
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const DEFAULT_FALLTHROUGH_COMMENT = /falls?\s?through/iu;
/**
* Checks whether or not a given case has a fallthrough comment.
* @param {ASTNode} caseWhichFallsThrough SwitchCase node which falls through.
* @param {ASTNode} subsequentCase The case after caseWhichFallsThrough.
* @param {RuleContext} context A rule context which stores comments.
* @param {RegExp} fallthroughCommentPattern A pattern to match comment to.
* @returns {boolean} `true` if the case has a valid fallthrough comment.
*/
function hasFallthroughComment(caseWhichFallsThrough, subsequentCase, context, fallthroughCommentPattern) {
const sourceCode = context.getSourceCode();
if (caseWhichFallsThrough.consequent.length === 1 && caseWhichFallsThrough.consequent[0].type === "BlockStatement") {
const trailingCloseBrace = sourceCode.getLastToken(caseWhichFallsThrough.consequent[0]);
const commentInBlock = sourceCode.getCommentsBefore(trailingCloseBrace).pop();
if (commentInBlock && fallthroughCommentPattern.test(commentInBlock.value)) {
return true;
}
}
const comment = sourceCode.getCommentsBefore(subsequentCase).pop();
return Boolean(comment && fallthroughCommentPattern.test(comment.value));
}
/**
* Checks whether or not a given code path segment is reachable.
* @param {CodePathSegment} segment A CodePathSegment to check.
* @returns {boolean} `true` if the segment is reachable.
*/
function isReachable(segment) {
return segment.reachable;
}
/**
* Checks whether a node and a token are separated by blank lines
* @param {ASTNode} node The node to check
* @param {Token} token The token to compare against
* @returns {boolean} `true` if there are blank lines between node and token
*/
function hasBlankLinesBetween(node, token) {
return token.loc.start.line > node.loc.end.line + 1;
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "problem",
docs: {
description: "Disallow fallthrough of `case` statements",
recommended: true,
url: "https://eslint.org/docs/rules/no-fallthrough"
},
schema: [
{
type: "object",
properties: {
commentPattern: {
type: "string",
default: ""
},
allowEmptyCase: {
type: "boolean",
default: false
}
},
additionalProperties: false
}
],
messages: {
case: "Expected a 'break' statement before 'case'.",
default: "Expected a 'break' statement before 'default'."
}
},
create(context) {
const options = context.options[0] || {};
let currentCodePath = null;
const sourceCode = context.getSourceCode();
const allowEmptyCase = options.allowEmptyCase || false;
/*
* We need to use leading comments of the next SwitchCase node because
* trailing comments is wrong if semicolons are omitted.
*/
let fallthroughCase = null;
let fallthroughCommentPattern = null;
if (options.commentPattern) {
fallthroughCommentPattern = new RegExp(options.commentPattern, "u");
} else {
fallthroughCommentPattern = DEFAULT_FALLTHROUGH_COMMENT;
}
return {
onCodePathStart(codePath) {
currentCodePath = codePath;
},
onCodePathEnd() {
currentCodePath = currentCodePath.upper;
},
SwitchCase(node) {
/*
* Checks whether or not there is a fallthrough comment.
* And reports the previous fallthrough node if that does not exist.
*/
if (fallthroughCase && (!hasFallthroughComment(fallthroughCase, node, context, fallthroughCommentPattern))) {
context.report({
messageId: node.test ? "case" : "default",
node
});
}
fallthroughCase = null;
},
"SwitchCase:exit"(node) {
const nextToken = sourceCode.getTokenAfter(node);
/*
* `reachable` meant fall through because statements preceded by
* `break`, `return`, or `throw` are unreachable.
* And allows empty cases and the last case.
*/
if (currentCodePath.currentSegments.some(isReachable) &&
(node.consequent.length > 0 || (!allowEmptyCase && hasBlankLinesBetween(node, nextToken))) &&
node.parent.cases[node.parent.cases.length - 1] !== node) {
fallthroughCase = node;
}
}
};
}
};
|
