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eb39fafa DC |
1 | /** |
2 | * @fileoverview Rule to disallow a negated condition | |
3 | * @author Alberto RodrÃguez | |
4 | */ | |
5 | "use strict"; | |
6 | ||
7 | //------------------------------------------------------------------------------ | |
8 | // Rule Definition | |
9 | //------------------------------------------------------------------------------ | |
10 | ||
34eeec05 | 11 | /** @type {import('../shared/types').Rule} */ |
eb39fafa DC |
12 | module.exports = { |
13 | meta: { | |
14 | type: "suggestion", | |
15 | ||
16 | docs: { | |
17 | description: "disallow negated conditions", | |
eb39fafa DC |
18 | recommended: false, |
19 | url: "https://eslint.org/docs/rules/no-negated-condition" | |
20 | }, | |
21 | ||
22 | schema: [], | |
23 | ||
24 | messages: { | |
25 | unexpectedNegated: "Unexpected negated condition." | |
26 | } | |
27 | }, | |
28 | ||
29 | create(context) { | |
30 | ||
31 | /** | |
32 | * Determines if a given node is an if-else without a condition on the else | |
33 | * @param {ASTNode} node The node to check. | |
34 | * @returns {boolean} True if the node has an else without an if. | |
35 | * @private | |
36 | */ | |
37 | function hasElseWithoutCondition(node) { | |
38 | return node.alternate && node.alternate.type !== "IfStatement"; | |
39 | } | |
40 | ||
41 | /** | |
42 | * Determines if a given node is a negated unary expression | |
43 | * @param {Object} test The test object to check. | |
44 | * @returns {boolean} True if the node is a negated unary expression. | |
45 | * @private | |
46 | */ | |
47 | function isNegatedUnaryExpression(test) { | |
48 | return test.type === "UnaryExpression" && test.operator === "!"; | |
49 | } | |
50 | ||
51 | /** | |
52 | * Determines if a given node is a negated binary expression | |
53 | * @param {Test} test The test to check. | |
54 | * @returns {boolean} True if the node is a negated binary expression. | |
55 | * @private | |
56 | */ | |
57 | function isNegatedBinaryExpression(test) { | |
58 | return test.type === "BinaryExpression" && | |
59 | (test.operator === "!=" || test.operator === "!=="); | |
60 | } | |
61 | ||
62 | /** | |
63 | * Determines if a given node has a negated if expression | |
64 | * @param {ASTNode} node The node to check. | |
65 | * @returns {boolean} True if the node has a negated if expression. | |
66 | * @private | |
67 | */ | |
68 | function isNegatedIf(node) { | |
69 | return isNegatedUnaryExpression(node.test) || isNegatedBinaryExpression(node.test); | |
70 | } | |
71 | ||
72 | return { | |
73 | IfStatement(node) { | |
74 | if (!hasElseWithoutCondition(node)) { | |
75 | return; | |
76 | } | |
77 | ||
78 | if (isNegatedIf(node)) { | |
79 | context.report({ | |
80 | node, | |
81 | messageId: "unexpectedNegated" | |
82 | }); | |
83 | } | |
84 | }, | |
85 | ConditionalExpression(node) { | |
86 | if (isNegatedIf(node)) { | |
87 | context.report({ | |
88 | node, | |
89 | messageId: "unexpectedNegated" | |
90 | }); | |
91 | } | |
92 | } | |
93 | }; | |
94 | } | |
95 | }; |