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node_modules/eslint/lib/rules/no-extra-bind.js

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+/**
+ * @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) {
+        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) {
+            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 = sourceCode
+                        .getFirstTokenBetween(node.parent.object, node.parent.property, astUtils.isNotClosingParenToken);
+                    const lastTokenToRemove = sourceCode.getLastToken(node.parent.parent);
+
+                    if (sourceCode.commentsExistBetween(firstTokenToRemove, lastTokenToRemove)) {
+                        return null;
+                    }
+
+                    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 &&
+                grandparent.arguments[0].type !== "SpreadElement" &&
+                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
+        };
+    }
+};