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eb39fafa DC |
1 | /** |
2 | * @fileoverview A rule to suggest using of the spread operator instead of `.apply()`. | |
3 | * @author Toru Nagashima | |
4 | */ | |
5 | ||
6 | "use strict"; | |
7 | ||
8 | const astUtils = require("./utils/ast-utils"); | |
9 | ||
10 | //------------------------------------------------------------------------------ | |
11 | // Helpers | |
12 | //------------------------------------------------------------------------------ | |
13 | ||
14 | /** | |
15 | * Checks whether or not a node is a `.apply()` for variadic. | |
16 | * @param {ASTNode} node A CallExpression node to check. | |
17 | * @returns {boolean} Whether or not the node is a `.apply()` for variadic. | |
18 | */ | |
19 | function isVariadicApplyCalling(node) { | |
20 | return ( | |
6f036462 | 21 | astUtils.isSpecificMemberAccess(node.callee, null, "apply") && |
eb39fafa DC |
22 | node.arguments.length === 2 && |
23 | node.arguments[1].type !== "ArrayExpression" && | |
24 | node.arguments[1].type !== "SpreadElement" | |
25 | ); | |
26 | } | |
27 | ||
eb39fafa DC |
28 | /** |
29 | * Checks whether or not `thisArg` is not changed by `.apply()`. | |
30 | * @param {ASTNode|null} expectedThis The node that is the owner of the applied function. | |
31 | * @param {ASTNode} thisArg The node that is given to the first argument of the `.apply()`. | |
32 | * @param {RuleContext} context The ESLint rule context object. | |
33 | * @returns {boolean} Whether or not `thisArg` is not changed by `.apply()`. | |
34 | */ | |
35 | function isValidThisArg(expectedThis, thisArg, context) { | |
36 | if (!expectedThis) { | |
37 | return astUtils.isNullOrUndefined(thisArg); | |
38 | } | |
39 | return astUtils.equalTokens(expectedThis, thisArg, context); | |
40 | } | |
41 | ||
42 | //------------------------------------------------------------------------------ | |
43 | // Rule Definition | |
44 | //------------------------------------------------------------------------------ | |
45 | ||
46 | module.exports = { | |
47 | meta: { | |
48 | type: "suggestion", | |
49 | ||
50 | docs: { | |
51 | description: "require spread operators instead of `.apply()`", | |
eb39fafa DC |
52 | recommended: false, |
53 | url: "https://eslint.org/docs/rules/prefer-spread" | |
54 | }, | |
55 | ||
56 | schema: [], | |
57 | fixable: null, | |
58 | ||
59 | messages: { | |
60 | preferSpread: "Use the spread operator instead of '.apply()'." | |
61 | } | |
62 | }, | |
63 | ||
64 | create(context) { | |
65 | const sourceCode = context.getSourceCode(); | |
66 | ||
67 | return { | |
68 | CallExpression(node) { | |
69 | if (!isVariadicApplyCalling(node)) { | |
70 | return; | |
71 | } | |
72 | ||
6f036462 | 73 | const applied = astUtils.skipChainExpression(astUtils.skipChainExpression(node.callee).object); |
eb39fafa DC |
74 | const expectedThis = (applied.type === "MemberExpression") ? applied.object : null; |
75 | const thisArg = node.arguments[0]; | |
76 | ||
77 | if (isValidThisArg(expectedThis, thisArg, sourceCode)) { | |
78 | context.report({ | |
79 | node, | |
80 | messageId: "preferSpread" | |
81 | }); | |
82 | } | |
83 | } | |
84 | }; | |
85 | } | |
86 | }; |