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eb39fafa DC |
1 | /** |
2 | * @fileoverview Rule to disallow uses of await inside of loops. | |
3 | * @author Nat Mote (nmote) | |
4 | */ | |
5 | "use strict"; | |
6 | ||
7 | /** | |
8 | * Check whether it should stop traversing ancestors at the given node. | |
9 | * @param {ASTNode} node A node to check. | |
10 | * @returns {boolean} `true` if it should stop traversing. | |
11 | */ | |
12 | function isBoundary(node) { | |
13 | const t = node.type; | |
14 | ||
15 | return ( | |
16 | t === "FunctionDeclaration" || | |
17 | t === "FunctionExpression" || | |
18 | t === "ArrowFunctionExpression" || | |
19 | ||
20 | /* | |
21 | * Don't report the await expressions on for-await-of loop since it's | |
22 | * asynchronous iteration intentionally. | |
23 | */ | |
24 | (t === "ForOfStatement" && node.await === true) | |
25 | ); | |
26 | } | |
27 | ||
28 | /** | |
29 | * Check whether the given node is in loop. | |
30 | * @param {ASTNode} node A node to check. | |
31 | * @param {ASTNode} parent A parent node to check. | |
32 | * @returns {boolean} `true` if the node is in loop. | |
33 | */ | |
34 | function isLooped(node, parent) { | |
35 | switch (parent.type) { | |
36 | case "ForStatement": | |
37 | return ( | |
38 | node === parent.test || | |
39 | node === parent.update || | |
40 | node === parent.body | |
41 | ); | |
42 | ||
43 | case "ForOfStatement": | |
44 | case "ForInStatement": | |
45 | return node === parent.body; | |
46 | ||
47 | case "WhileStatement": | |
48 | case "DoWhileStatement": | |
49 | return node === parent.test || node === parent.body; | |
50 | ||
51 | default: | |
52 | return false; | |
53 | } | |
54 | } | |
55 | ||
34eeec05 | 56 | /** @type {import('../shared/types').Rule} */ |
eb39fafa DC |
57 | module.exports = { |
58 | meta: { | |
59 | type: "problem", | |
60 | ||
61 | docs: { | |
8f9d1d4d | 62 | description: "Disallow `await` inside of loops", |
eb39fafa | 63 | recommended: false, |
f2a92ac6 | 64 | url: "https://eslint.org/docs/latest/rules/no-await-in-loop" |
eb39fafa DC |
65 | }, |
66 | ||
67 | schema: [], | |
68 | ||
69 | messages: { | |
70 | unexpectedAwait: "Unexpected `await` inside a loop." | |
71 | } | |
72 | }, | |
73 | create(context) { | |
74 | ||
75 | /** | |
76 | * Validate an await expression. | |
77 | * @param {ASTNode} awaitNode An AwaitExpression or ForOfStatement node to validate. | |
78 | * @returns {void} | |
79 | */ | |
80 | function validate(awaitNode) { | |
81 | if (awaitNode.type === "ForOfStatement" && !awaitNode.await) { | |
82 | return; | |
83 | } | |
84 | ||
85 | let node = awaitNode; | |
86 | let parent = node.parent; | |
87 | ||
88 | while (parent && !isBoundary(parent)) { | |
89 | if (isLooped(node, parent)) { | |
90 | context.report({ | |
91 | node: awaitNode, | |
92 | messageId: "unexpectedAwait" | |
93 | }); | |
94 | return; | |
95 | } | |
96 | node = parent; | |
97 | parent = parent.parent; | |
98 | } | |
99 | } | |
100 | ||
101 | return { | |
102 | AwaitExpression: validate, | |
103 | ForOfStatement: validate | |
104 | }; | |
105 | } | |
106 | }; |