146 lines
4.6 KiB
JavaScript
146 lines
4.6 KiB
JavaScript
/**
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* @fileoverview Rule to flag unnecessary bind calls
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* @author Bence Dányi <bence@danyi.me>
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const astUtils = require("../ast-utils");
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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docs: {
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description: "disallow unnecessary calls to `.bind()`",
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category: "Best Practices",
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recommended: false
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},
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schema: [],
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fixable: "code"
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},
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create(context) {
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let scopeInfo = null;
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/**
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* Reports a given function node.
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*
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* @param {ASTNode} node - A node to report. This is a FunctionExpression or
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* an ArrowFunctionExpression.
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* @returns {void}
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*/
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function report(node) {
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context.report({
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node: node.parent.parent,
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message: "The function binding is unnecessary.",
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loc: node.parent.property.loc.start,
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fix(fixer) {
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const firstTokenToRemove = context.getSourceCode()
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.getFirstTokenBetween(node.parent.object, node.parent.property, astUtils.isNotClosingParenToken);
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return fixer.removeRange([firstTokenToRemove.range[0], node.parent.parent.range[1]]);
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}
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});
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}
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/**
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* Checks whether or not a given function node is the callee of `.bind()`
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* method.
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*
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* e.g. `(function() {}.bind(foo))`
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*
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* @param {ASTNode} node - A node to report. This is a FunctionExpression or
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* an ArrowFunctionExpression.
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* @returns {boolean} `true` if the node is the callee of `.bind()` method.
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*/
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function isCalleeOfBindMethod(node) {
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const parent = node.parent;
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const grandparent = parent.parent;
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return (
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grandparent &&
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grandparent.type === "CallExpression" &&
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grandparent.callee === parent &&
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grandparent.arguments.length === 1 &&
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parent.type === "MemberExpression" &&
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parent.object === node &&
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astUtils.getStaticPropertyName(parent) === "bind"
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);
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}
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/**
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* Adds a scope information object to the stack.
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*
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* @param {ASTNode} node - A node to add. This node is a FunctionExpression
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* or a FunctionDeclaration node.
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* @returns {void}
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*/
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function enterFunction(node) {
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scopeInfo = {
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isBound: isCalleeOfBindMethod(node),
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thisFound: false,
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upper: scopeInfo
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};
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}
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/**
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* Removes the scope information object from the top of the stack.
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* At the same time, this reports the function node if the function has
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* `.bind()` and the `this` keywords found.
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*
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* @param {ASTNode} node - A node to remove. This node is a
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* FunctionExpression or a FunctionDeclaration node.
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* @returns {void}
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*/
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function exitFunction(node) {
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if (scopeInfo.isBound && !scopeInfo.thisFound) {
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report(node);
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}
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scopeInfo = scopeInfo.upper;
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}
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/**
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* Reports a given arrow function if the function is callee of `.bind()`
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* method.
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*
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* @param {ASTNode} node - A node to report. This node is an
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* ArrowFunctionExpression.
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* @returns {void}
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*/
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function exitArrowFunction(node) {
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if (isCalleeOfBindMethod(node)) {
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report(node);
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}
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}
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/**
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* Set the mark as the `this` keyword was found in this scope.
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*
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* @returns {void}
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*/
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function markAsThisFound() {
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if (scopeInfo) {
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scopeInfo.thisFound = true;
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}
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}
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return {
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"ArrowFunctionExpression:exit": exitArrowFunction,
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FunctionDeclaration: enterFunction,
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"FunctionDeclaration:exit": exitFunction,
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FunctionExpression: enterFunction,
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"FunctionExpression:exit": exitFunction,
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ThisExpression: markAsThisFound
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};
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}
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};
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