no-useless-call.js
3.17 KB
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
/**
* @fileoverview A rule to disallow unnecessary `.call()` and `.apply()`.
* @author Toru Nagashima
* @copyright 2015 Toru Nagashima. All rights reserved.
*/
"use strict";
var astUtils = require("../ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether or not a node is a `.call()`/`.apply()`.
* @param {ASTNode} node - A CallExpression node to check.
* @returns {boolean} Whether or not the node is a `.call()`/`.apply()`.
*/
function isCallOrNonVariadicApply(node) {
return (
node.callee.type === "MemberExpression" &&
node.callee.property.type === "Identifier" &&
node.callee.computed === false &&
(
(node.callee.property.name === "call" && node.arguments.length >= 1) ||
(node.callee.property.name === "apply" && node.arguments.length === 2 && node.arguments[1].type === "ArrayExpression")
)
);
}
/**
* Checks whether or not the tokens of two given nodes are same.
* @param {ASTNode} left - A node 1 to compare.
* @param {ASTNode} right - A node 2 to compare.
* @param {RuleContext} context - The ESLint rule context object.
* @returns {boolean} the source code for the given node.
*/
function equalTokens(left, right, context) {
var tokensL = context.getTokens(left);
var tokensR = context.getTokens(right);
if (tokensL.length !== tokensR.length) {
return false;
}
for (var i = 0; i < tokensL.length; ++i) {
if (tokensL[i].type !== tokensR[i].type ||
tokensL[i].value !== tokensR[i].value
) {
return false;
}
}
return true;
}
/**
* Checks whether or not `thisArg` is not changed by `.call()`/`.apply()`.
* @param {ASTNode|null} expectedThis - The node that is the owner of the applied function.
* @param {ASTNode} thisArg - The node that is given to the first argument of the `.call()`/`.apply()`.
* @param {RuleContext} context - The ESLint rule context object.
* @returns {boolean} Whether or not `thisArg` is not changed by `.call()`/`.apply()`.
*/
function isValidThisArg(expectedThis, thisArg, context) {
if (!expectedThis) {
return astUtils.isNullOrUndefined(thisArg);
}
return equalTokens(expectedThis, thisArg, context);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = function(context) {
return {
"CallExpression": function(node) {
if (!isCallOrNonVariadicApply(node)) {
return;
}
var applied = node.callee.object;
var expectedThis = (applied.type === "MemberExpression") ? applied.object : null;
var thisArg = node.arguments[0];
if (isValidThisArg(expectedThis, thisArg, context)) {
context.report(
node,
"unnecessary \".{{name}}()\".",
{name: node.callee.property.name});
}
}
};
};
module.exports.schema = [];