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
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
|
/**
* @fileoverview Rule to enforce return statements in callbacks of array's methods
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const lodash = require("lodash");
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const TARGET_NODE_TYPE = /^(?:Arrow)?FunctionExpression$/u;
const TARGET_METHODS = /^(?:every|filter|find(?:Index)?|map|reduce(?:Right)?|some|sort)$/u;
/**
* Checks a given code path segment is reachable.
* @param {CodePathSegment} segment A segment to check.
* @returns {boolean} `true` if the segment is reachable.
*/
function isReachable(segment) {
return segment.reachable;
}
/**
* Gets a readable location.
*
* - FunctionExpression -> the function name or `function` keyword.
* - ArrowFunctionExpression -> `=>` token.
* @param {ASTNode} node A function node to get.
* @param {SourceCode} sourceCode A source code to get tokens.
* @returns {ASTNode|Token} The node or the token of a location.
*/
function getLocation(node, sourceCode) {
if (node.type === "ArrowFunctionExpression") {
return sourceCode.getTokenBefore(node.body);
}
return node.id || node;
}
/**
* Checks a given node is a MemberExpression node which has the specified name's
* property.
* @param {ASTNode} node A node to check.
* @returns {boolean} `true` if the node is a MemberExpression node which has
* the specified name's property
*/
function isTargetMethod(node) {
return (
node.type === "MemberExpression" &&
TARGET_METHODS.test(astUtils.getStaticPropertyName(node) || "")
);
}
/**
* Checks whether or not a given node is a function expression which is the
* callback of an array method.
* @param {ASTNode} node A node to check. This is one of
* FunctionExpression or ArrowFunctionExpression.
* @returns {boolean} `true` if the node is the callback of an array method.
*/
function isCallbackOfArrayMethod(node) {
let currentNode = node;
while (currentNode) {
const parent = currentNode.parent;
switch (parent.type) {
/*
* Looks up the destination. e.g.,
* foo.every(nativeFoo || function foo() { ... });
*/
case "LogicalExpression":
case "ConditionalExpression":
currentNode = parent;
break;
/*
* If the upper function is IIFE, checks the destination of the return value.
* e.g.
* foo.every((function() {
* // setup...
* return function callback() { ... };
* })());
*/
case "ReturnStatement": {
const func = astUtils.getUpperFunction(parent);
if (func === null || !astUtils.isCallee(func)) {
return false;
}
currentNode = func.parent;
break;
}
/*
* e.g.
* Array.from([], function() {});
* list.every(function() {});
*/
case "CallExpression":
if (astUtils.isArrayFromMethod(parent.callee)) {
return (
parent.arguments.length >= 2 &&
parent.arguments[1] === currentNode
);
}
if (isTargetMethod(parent.callee)) {
return (
parent.arguments.length >= 1 &&
parent.arguments[0] === currentNode
);
}
return false;
// Otherwise this node is not target.
default:
return false;
}
}
/* istanbul ignore next: unreachable */
return false;
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "problem",
docs: {
description: "enforce `return` statements in callbacks of array methods",
category: "Best Practices",
recommended: false,
url: "https://eslint.org/docs/rules/array-callback-return"
},
schema: [
{
type: "object",
properties: {
allowImplicit: {
type: "boolean",
default: false
}
},
additionalProperties: false
}
],
messages: {
expectedAtEnd: "Expected to return a value at the end of {{name}}.",
expectedInside: "Expected to return a value in {{name}}.",
expectedReturnValue: "{{name}} expected a return value."
}
},
create(context) {
const options = context.options[0] || { allowImplicit: false };
let funcInfo = {
upper: null,
codePath: null,
hasReturn: false,
shouldCheck: false,
node: null
};
/**
* Checks whether or not the last code path segment is reachable.
* Then reports this function if the segment is reachable.
*
* If the last code path segment is reachable, there are paths which are not
* returned or thrown.
* @param {ASTNode} node A node to check.
* @returns {void}
*/
function checkLastSegment(node) {
if (funcInfo.shouldCheck &&
funcInfo.codePath.currentSegments.some(isReachable)
) {
context.report({
node,
loc: getLocation(node, context.getSourceCode()).loc.start,
messageId: funcInfo.hasReturn
? "expectedAtEnd"
: "expectedInside",
data: {
name: astUtils.getFunctionNameWithKind(funcInfo.node)
}
});
}
}
return {
// Stacks this function's information.
onCodePathStart(codePath, node) {
funcInfo = {
upper: funcInfo,
codePath,
hasReturn: false,
shouldCheck:
TARGET_NODE_TYPE.test(node.type) &&
node.body.type === "BlockStatement" &&
isCallbackOfArrayMethod(node) &&
!node.async &&
!node.generator,
node
};
},
// Pops this function's information.
onCodePathEnd() {
funcInfo = funcInfo.upper;
},
// Checks the return statement is valid.
ReturnStatement(node) {
if (funcInfo.shouldCheck) {
funcInfo.hasReturn = true;
// if allowImplicit: false, should also check node.argument
if (!options.allowImplicit && !node.argument) {
context.report({
node,
messageId: "expectedReturnValue",
data: {
name: lodash.upperFirst(astUtils.getFunctionNameWithKind(funcInfo.node))
}
});
}
}
},
// Reports a given function if the last path is reachable.
"FunctionExpression:exit": checkLastSegment,
"ArrowFunctionExpression:exit": checkLastSegment
};
}
};
|
