/
no-useless-undefined.js
169 lines (146 loc) · 3.89 KB
/
no-useless-undefined.js
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
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
'use strict';
const {isCommaToken} = require('eslint-utils');
const getDocumentationUrl = require('./utils/get-documentation-url');
const messageId = 'no-useless-undefined';
const messages = {
[messageId]: 'Do not use useless `undefined`.'
};
const getSelector = (parent, property) =>
`${parent} > Identifier.${property}[name="undefined"]`;
// `return undefined`
const returnSelector = getSelector('ReturnStatement', 'argument');
// `yield undefined`
const yieldSelector = getSelector('YieldExpression[delegate=false]', 'argument');
// `() => undefined`
const arrowFunctionSelector = getSelector('ArrowFunctionExpression', 'body');
// `let foo = undefined` / `var foo = undefined`
const variableInitSelector = getSelector(
[
'VariableDeclaration',
'[kind!="const"]',
'>',
'VariableDeclarator'
].join(''),
'init'
);
// `const {foo = undefined} = {}`
const assignmentPatternSelector = getSelector('AssignmentPattern', 'right');
const isUndefined = node => node && node.type === 'Identifier' && node.name === 'undefined';
const compareFunctionNames = new Set([
'is',
'equal',
'notEqual',
'strictEqual',
'notStrictEqual',
'propertyVal',
'notPropertyVal',
'not',
'include',
'property',
'toBe',
'toHaveBeenCalledWith',
'toContain',
'toContainEqual',
'toEqual',
'same',
'notSame',
'strictSame',
'strictNotSame'
]);
const isCompareFunction = node => {
let name;
if (node.type === 'Identifier') {
name = node.name;
} else if (
node.type === 'MemberExpression' &&
node.computed === false &&
node.property &&
node.property.type === 'Identifier'
) {
name = node.property.name;
}
return compareFunctionNames.has(name);
};
const create = context => {
const listener = fix => node => {
context.report({
node,
messageId,
fix: fixer => fix(node, fixer)
});
};
const code = context.getSourceCode().text;
const removeNodeAndLeadingSpace = (node, fixer) => {
const textBefore = code.slice(0, node.range[0]);
return fixer.removeRange([
node.range[0] - (textBefore.length - textBefore.trim().length),
node.range[1]
]);
};
return {
[returnSelector]: listener(removeNodeAndLeadingSpace),
[yieldSelector]: listener(removeNodeAndLeadingSpace),
[arrowFunctionSelector]: listener(
(node, fixer) => fixer.replaceText(node, '{}')
),
[variableInitSelector]: listener(
(node, fixer) => fixer.removeRange([node.parent.id.range[1], node.range[1]])
),
[assignmentPatternSelector]: listener(
(node, fixer) => fixer.removeRange([node.parent.left.range[1], node.range[1]])
),
CallExpression: node => {
if (isCompareFunction(node.callee)) {
return;
}
const argumentNodes = node.arguments;
const undefinedArguments = [];
for (let index = argumentNodes.length - 1; index >= 0; index--) {
const node = argumentNodes[index];
if (isUndefined(node)) {
undefinedArguments.unshift(node);
} else {
break;
}
}
if (undefinedArguments.length === 0) {
return;
}
const firstUndefined = undefinedArguments[0];
const lastUndefined = undefinedArguments[undefinedArguments.length - 1];
context.report({
messageId,
loc: {
start: firstUndefined.loc.start,
end: lastUndefined.loc.end
},
fix: fixer => {
let start = firstUndefined.range[0];
let end = lastUndefined.range[1];
const previousArgument = argumentNodes[argumentNodes.length - undefinedArguments.length - 1];
if (previousArgument) {
start = previousArgument.range[1];
} else {
// If all arguments removed, and there is trailing comma, we need remove it.
const tokenAfter = context.getTokenAfter(lastUndefined);
if (isCommaToken(tokenAfter)) {
end = tokenAfter.range[1];
}
}
return fixer.removeRange([start, end]);
}
});
}
};
};
module.exports = {
create,
meta: {
type: 'suggestion',
docs: {
url: getDocumentationUrl(__filename)
},
messages,
fixable: 'code'
}
};