Current File : /var/www/html/node_modules/eslint/lib/rules/no-extra-bind.js
/**
* @fileoverview Rule to flag unnecessary bind calls
* @author Bence Dányi <bence@danyi.me>
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const SIDE_EFFECT_FREE_NODE_TYPES = new Set(["Literal", "Identifier", "ThisExpression", "FunctionExpression"]);
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "disallow unnecessary calls to `.bind()`",
recommended: false,
url: "https://eslint.org/docs/rules/no-extra-bind"
},
schema: [],
fixable: "code",
messages: {
unexpected: "The function binding is unnecessary."
}
},
create(context) {
const sourceCode = context.getSourceCode();
let scopeInfo = null;
/**
* Checks if a node is free of side effects.
*
* This check is stricter than it needs to be, in order to keep the implementation simple.
* @param {ASTNode} node A node to check.
* @returns {boolean} True if the node is known to be side-effect free, false otherwise.
*/
function isSideEffectFree(node) {
return SIDE_EFFECT_FREE_NODE_TYPES.has(node.type);
}
/**
* Reports a given function node.
* @param {ASTNode} node A node to report. This is a FunctionExpression or
* an ArrowFunctionExpression.
* @returns {void}
*/
function report(node) {
const memberNode = node.parent;
const callNode = memberNode.parent.type === "ChainExpression"
? memberNode.parent.parent
: memberNode.parent;
context.report({
node: callNode,
messageId: "unexpected",
loc: memberNode.property.loc,
fix(fixer) {
if (!isSideEffectFree(callNode.arguments[0])) {
return null;
}
/*
* The list of the first/last token pair of a removal range.
* This is two parts because closing parentheses may exist between the method name and arguments.
* E.g. `(function(){}.bind ) (obj)`
* ^^^^^ ^^^^^ < removal ranges
* E.g. `(function(){}?.['bind'] ) ?.(obj)`
* ^^^^^^^^^^ ^^^^^^^ < removal ranges
*/
const tokenPairs = [
[
// `.`, `?.`, or `[` token.
sourceCode.getTokenAfter(
memberNode.object,
astUtils.isNotClosingParenToken
),
// property name or `]` token.
sourceCode.getLastToken(memberNode)
],
[
// `?.` or `(` token of arguments.
sourceCode.getTokenAfter(
memberNode,
astUtils.isNotClosingParenToken
),
// `)` token of arguments.
sourceCode.getLastToken(callNode)
]
];
const firstTokenToRemove = tokenPairs[0][0];
const lastTokenToRemove = tokenPairs[1][1];
if (sourceCode.commentsExistBetween(firstTokenToRemove, lastTokenToRemove)) {
return null;
}
return tokenPairs.map(([start, end]) =>
fixer.removeRange([start.range[0], end.range[1]]));
}
});
}
/**
* Checks whether or not a given function node is the callee of `.bind()`
* method.
*
* e.g. `(function() {}.bind(foo))`
* @param {ASTNode} node A node to report. This is a FunctionExpression or
* an ArrowFunctionExpression.
* @returns {boolean} `true` if the node is the callee of `.bind()` method.
*/
function isCalleeOfBindMethod(node) {
if (!astUtils.isSpecificMemberAccess(node.parent, null, "bind")) {
return false;
}
// The node of `*.bind` member access.
const bindNode = node.parent.parent.type === "ChainExpression"
? node.parent.parent
: node.parent;
return (
bindNode.parent.type === "CallExpression" &&
bindNode.parent.callee === bindNode &&
bindNode.parent.arguments.length === 1 &&
bindNode.parent.arguments[0].type !== "SpreadElement"
);
}
/**
* Adds a scope information object to the stack.
* @param {ASTNode} node A node to add. This node is a FunctionExpression
* or a FunctionDeclaration node.
* @returns {void}
*/
function enterFunction(node) {
scopeInfo = {
isBound: isCalleeOfBindMethod(node),
thisFound: false,
upper: scopeInfo
};
}
/**
* Removes the scope information object from the top of the stack.
* At the same time, this reports the function node if the function has
* `.bind()` and the `this` keywords found.
* @param {ASTNode} node A node to remove. This node is a
* FunctionExpression or a FunctionDeclaration node.
* @returns {void}
*/
function exitFunction(node) {
if (scopeInfo.isBound && !scopeInfo.thisFound) {
report(node);
}
scopeInfo = scopeInfo.upper;
}
/**
* Reports a given arrow function if the function is callee of `.bind()`
* method.
* @param {ASTNode} node A node to report. This node is an
* ArrowFunctionExpression.
* @returns {void}
*/
function exitArrowFunction(node) {
if (isCalleeOfBindMethod(node)) {
report(node);
}
}
/**
* Set the mark as the `this` keyword was found in this scope.
* @returns {void}
*/
function markAsThisFound() {
if (scopeInfo) {
scopeInfo.thisFound = true;
}
}
return {
"ArrowFunctionExpression:exit": exitArrowFunction,
FunctionDeclaration: enterFunction,
"FunctionDeclaration:exit": exitFunction,
FunctionExpression: enterFunction,
"FunctionExpression:exit": exitFunction,
ThisExpression: markAsThisFound
};
}
};
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