1 | /**
|
2 | * @fileoverview Rule to flag unnecessary bind calls
|
3 | * @author Bence Dányi <bence@danyi.me>
|
4 | */
|
5 | ;
|
6 |
|
7 | //------------------------------------------------------------------------------
|
8 | // Requirements
|
9 | //------------------------------------------------------------------------------
|
10 |
|
11 | const astUtils = require("./utils/ast-utils");
|
12 |
|
13 | //------------------------------------------------------------------------------
|
14 | // Helpers
|
15 | //------------------------------------------------------------------------------
|
16 |
|
17 | const SIDE_EFFECT_FREE_NODE_TYPES = new Set(["Literal", "Identifier", "ThisExpression", "FunctionExpression"]);
|
18 |
|
19 | //------------------------------------------------------------------------------
|
20 | // Rule Definition
|
21 | //------------------------------------------------------------------------------
|
22 |
|
23 | module.exports = {
|
24 | meta: {
|
25 | type: "suggestion",
|
26 |
|
27 | docs: {
|
28 | description: "disallow unnecessary calls to `.bind()`",
|
29 | category: "Best Practices",
|
30 | recommended: false,
|
31 | url: "https://eslint.org/docs/rules/no-extra-bind"
|
32 | },
|
33 |
|
34 | schema: [],
|
35 | fixable: "code",
|
36 |
|
37 | messages: {
|
38 | unexpected: "The function binding is unnecessary."
|
39 | }
|
40 | },
|
41 |
|
42 | create(context) {
|
43 | const sourceCode = context.getSourceCode();
|
44 | let scopeInfo = null;
|
45 |
|
46 | /**
|
47 | * Checks if a node is free of side effects.
|
48 | *
|
49 | * This check is stricter than it needs to be, in order to keep the implementation simple.
|
50 | * @param {ASTNode} node A node to check.
|
51 | * @returns {boolean} True if the node is known to be side-effect free, false otherwise.
|
52 | */
|
53 | function isSideEffectFree(node) {
|
54 | return SIDE_EFFECT_FREE_NODE_TYPES.has(node.type);
|
55 | }
|
56 |
|
57 | /**
|
58 | * Reports a given function node.
|
59 | * @param {ASTNode} node A node to report. This is a FunctionExpression or
|
60 | * an ArrowFunctionExpression.
|
61 | * @returns {void}
|
62 | */
|
63 | function report(node) {
|
64 | const memberNode = node.parent;
|
65 | const callNode = memberNode.parent.type === "ChainExpression"
|
66 | ? memberNode.parent.parent
|
67 | : memberNode.parent;
|
68 |
|
69 | context.report({
|
70 | node: callNode,
|
71 | messageId: "unexpected",
|
72 | loc: memberNode.property.loc,
|
73 |
|
74 | fix(fixer) {
|
75 | if (!isSideEffectFree(callNode.arguments[0])) {
|
76 | return null;
|
77 | }
|
78 |
|
79 | /*
|
80 | * The list of the first/last token pair of a removal range.
|
81 | * This is two parts because closing parentheses may exist between the method name and arguments.
|
82 | * E.g. `(function(){}.bind ) (obj)`
|
83 | * ^^^^^ ^^^^^ < removal ranges
|
84 | * E.g. `(function(){}?.['bind'] ) ?.(obj)`
|
85 | * ^^^^^^^^^^ ^^^^^^^ < removal ranges
|
86 | */
|
87 | const tokenPairs = [
|
88 | [
|
89 |
|
90 | // `.`, `?.`, or `[` token.
|
91 | sourceCode.getTokenAfter(
|
92 | memberNode.object,
|
93 | astUtils.isNotClosingParenToken
|
94 | ),
|
95 |
|
96 | // property name or `]` token.
|
97 | sourceCode.getLastToken(memberNode)
|
98 | ],
|
99 | [
|
100 |
|
101 | // `?.` or `(` token of arguments.
|
102 | sourceCode.getTokenAfter(
|
103 | memberNode,
|
104 | astUtils.isNotClosingParenToken
|
105 | ),
|
106 |
|
107 | // `)` token of arguments.
|
108 | sourceCode.getLastToken(callNode)
|
109 | ]
|
110 | ];
|
111 | const firstTokenToRemove = tokenPairs[0][0];
|
112 | const lastTokenToRemove = tokenPairs[1][1];
|
113 |
|
114 | if (sourceCode.commentsExistBetween(firstTokenToRemove, lastTokenToRemove)) {
|
115 | return null;
|
116 | }
|
117 |
|
118 | return tokenPairs.map(([start, end]) =>
|
119 | fixer.removeRange([start.range[0], end.range[1]]));
|
120 | }
|
121 | });
|
122 | }
|
123 |
|
124 | /**
|
125 | * Checks whether or not a given function node is the callee of `.bind()`
|
126 | * method.
|
127 | *
|
128 | * e.g. `(function() {}.bind(foo))`
|
129 | * @param {ASTNode} node A node to report. This is a FunctionExpression or
|
130 | * an ArrowFunctionExpression.
|
131 | * @returns {boolean} `true` if the node is the callee of `.bind()` method.
|
132 | */
|
133 | function isCalleeOfBindMethod(node) {
|
134 | if (!astUtils.isSpecificMemberAccess(node.parent, null, "bind")) {
|
135 | return false;
|
136 | }
|
137 |
|
138 | // The node of `*.bind` member access.
|
139 | const bindNode = node.parent.parent.type === "ChainExpression"
|
140 | ? node.parent.parent
|
141 | : node.parent;
|
142 |
|
143 | return (
|
144 | bindNode.parent.type === "CallExpression" &&
|
145 | bindNode.parent.callee === bindNode &&
|
146 | bindNode.parent.arguments.length === 1 &&
|
147 | bindNode.parent.arguments[0].type !== "SpreadElement"
|
148 | );
|
149 | }
|
150 |
|
151 | /**
|
152 | * Adds a scope information object to the stack.
|
153 | * @param {ASTNode} node A node to add. This node is a FunctionExpression
|
154 | * or a FunctionDeclaration node.
|
155 | * @returns {void}
|
156 | */
|
157 | function enterFunction(node) {
|
158 | scopeInfo = {
|
159 | isBound: isCalleeOfBindMethod(node),
|
160 | thisFound: false,
|
161 | upper: scopeInfo
|
162 | };
|
163 | }
|
164 |
|
165 | /**
|
166 | * Removes the scope information object from the top of the stack.
|
167 | * At the same time, this reports the function node if the function has
|
168 | * `.bind()` and the `this` keywords found.
|
169 | * @param {ASTNode} node A node to remove. This node is a
|
170 | * FunctionExpression or a FunctionDeclaration node.
|
171 | * @returns {void}
|
172 | */
|
173 | function exitFunction(node) {
|
174 | if (scopeInfo.isBound && !scopeInfo.thisFound) {
|
175 | report(node);
|
176 | }
|
177 |
|
178 | scopeInfo = scopeInfo.upper;
|
179 | }
|
180 |
|
181 | /**
|
182 | * Reports a given arrow function if the function is callee of `.bind()`
|
183 | * method.
|
184 | * @param {ASTNode} node A node to report. This node is an
|
185 | * ArrowFunctionExpression.
|
186 | * @returns {void}
|
187 | */
|
188 | function exitArrowFunction(node) {
|
189 | if (isCalleeOfBindMethod(node)) {
|
190 | report(node);
|
191 | }
|
192 | }
|
193 |
|
194 | /**
|
195 | * Set the mark as the `this` keyword was found in this scope.
|
196 | * @returns {void}
|
197 | */
|
198 | function markAsThisFound() {
|
199 | if (scopeInfo) {
|
200 | scopeInfo.thisFound = true;
|
201 | }
|
202 | }
|
203 |
|
204 | return {
|
205 | "ArrowFunctionExpression:exit": exitArrowFunction,
|
206 | FunctionDeclaration: enterFunction,
|
207 | "FunctionDeclaration:exit": exitFunction,
|
208 | FunctionExpression: enterFunction,
|
209 | "FunctionExpression:exit": exitFunction,
|
210 | ThisExpression: markAsThisFound
|
211 | };
|
212 | }
|
213 | };
|