2 * @fileoverview Rule to flag unnecessary bind calls
3 * @author Bence Dányi <bence@danyi.me>
7 //------------------------------------------------------------------------------
9 //------------------------------------------------------------------------------
11 const astUtils
= require("./utils/ast-utils");
13 //------------------------------------------------------------------------------
15 //------------------------------------------------------------------------------
17 const SIDE_EFFECT_FREE_NODE_TYPES
= new Set(["Literal", "Identifier", "ThisExpression", "FunctionExpression"]);
19 //------------------------------------------------------------------------------
21 //------------------------------------------------------------------------------
23 /** @type {import('../shared/types').Rule} */
29 description
: "Disallow unnecessary calls to `.bind()`",
31 url
: "https://eslint.org/docs/rules/no-extra-bind"
38 unexpected
: "The function binding is unnecessary."
43 const sourceCode
= context
.getSourceCode();
47 * Checks if a node is free of side effects.
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.
53 function isSideEffectFree(node
) {
54 return SIDE_EFFECT_FREE_NODE_TYPES
.has(node
.type
);
58 * Reports a given function node.
59 * @param {ASTNode} node A node to report. This is a FunctionExpression or
60 * an ArrowFunctionExpression.
63 function report(node
) {
64 const memberNode
= node
.parent
;
65 const callNode
= memberNode
.parent
.type
=== "ChainExpression"
66 ? memberNode
.parent
.parent
71 messageId
: "unexpected",
72 loc
: memberNode
.property
.loc
,
75 if (!isSideEffectFree(callNode
.arguments
[0])) {
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
90 // `.`, `?.`, or `[` token.
91 sourceCode
.getTokenAfter(
93 astUtils
.isNotClosingParenToken
96 // property name or `]` token.
97 sourceCode
.getLastToken(memberNode
)
101 // `?.` or `(` token of arguments.
102 sourceCode
.getTokenAfter(
104 astUtils
.isNotClosingParenToken
107 // `)` token of arguments.
108 sourceCode
.getLastToken(callNode
)
111 const firstTokenToRemove
= tokenPairs
[0][0];
112 const lastTokenToRemove
= tokenPairs
[1][1];
114 if (sourceCode
.commentsExistBetween(firstTokenToRemove
, lastTokenToRemove
)) {
118 return tokenPairs
.map(([start
, end
]) =>
119 fixer
.removeRange([start
.range
[0], end
.range
[1]]));
125 * Checks whether or not a given function node is the callee of `.bind()`
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.
133 function isCalleeOfBindMethod(node
) {
134 if (!astUtils
.isSpecificMemberAccess(node
.parent
, null, "bind")) {
138 // The node of `*.bind` member access.
139 const bindNode
= node
.parent
.parent
.type
=== "ChainExpression"
144 bindNode
.parent
.type
=== "CallExpression" &&
145 bindNode
.parent
.callee
=== bindNode
&&
146 bindNode
.parent
.arguments
.length
=== 1 &&
147 bindNode
.parent
.arguments
[0].type
!== "SpreadElement"
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.
157 function enterFunction(node
) {
159 isBound
: isCalleeOfBindMethod(node
),
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.
173 function exitFunction(node
) {
174 if (scopeInfo
.isBound
&& !scopeInfo
.thisFound
) {
178 scopeInfo
= scopeInfo
.upper
;
182 * Reports a given arrow function if the function is callee of `.bind()`
184 * @param {ASTNode} node A node to report. This node is an
185 * ArrowFunctionExpression.
188 function exitArrowFunction(node
) {
189 if (isCalleeOfBindMethod(node
)) {
195 * Set the mark as the `this` keyword was found in this scope.
198 function markAsThisFound() {
200 scopeInfo
.thisFound
= true;
205 "ArrowFunctionExpression:exit": exitArrowFunction
,
206 FunctionDeclaration
: enterFunction
,
207 "FunctionDeclaration:exit": exitFunction
,
208 FunctionExpression
: enterFunction
,
209 "FunctionExpression:exit": exitFunction
,
210 ThisExpression
: markAsThisFound