| /** |
| * @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 |
| //------------------------------------------------------------------------------ |
| |
| module.exports = { |
| meta: { |
| type: "suggestion", |
| |
| docs: { |
| description: "disallow unnecessary calls to `.bind()`", |
| category: "Best Practices", |
| recommended: false, |
| url: "https://eslint.org/docs/rules/no-extra-bind" |
| }, |
| |
| schema: [], |
| fixable: "code", |
| |
| messages: { |
| unexpected: "The function binding is unnecessary." |
| } |
| }, |
| |
| create(context) { |
| 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) { |
| context.report({ |
| node: node.parent.parent, |
| messageId: "unexpected", |
| loc: node.parent.property.loc.start, |
| fix(fixer) { |
| if (node.parent.parent.arguments.length && !isSideEffectFree(node.parent.parent.arguments[0])) { |
| return null; |
| } |
| |
| const firstTokenToRemove = context.getSourceCode() |
| .getFirstTokenBetween(node.parent.object, node.parent.property, astUtils.isNotClosingParenToken); |
| |
| return fixer.removeRange([firstTokenToRemove.range[0], node.parent.parent.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) { |
| const parent = node.parent; |
| const grandparent = parent.parent; |
| |
| return ( |
| grandparent && |
| grandparent.type === "CallExpression" && |
| grandparent.callee === parent && |
| grandparent.arguments.length === 1 && |
| parent.type === "MemberExpression" && |
| parent.object === node && |
| astUtils.getStaticPropertyName(parent) === "bind" |
| ); |
| } |
| |
| /** |
| * 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 |
| }; |
| } |
| }; |