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qwen/nodejs/node_modules/eslint/lib/rules/eqeqeq.js

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+/**
+ * @fileoverview Rule to flag statements that use != and == instead of !== and ===
+ * @author Nicholas C. Zakas
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "Require the use of `===` and `!==`",
+            recommended: false,
+            url: "https://eslint.org/docs/latest/rules/eqeqeq"
+        },
+
+        schema: {
+            anyOf: [
+                {
+                    type: "array",
+                    items: [
+                        {
+                            enum: ["always"]
+                        },
+                        {
+                            type: "object",
+                            properties: {
+                                null: {
+                                    enum: ["always", "never", "ignore"]
+                                }
+                            },
+                            additionalProperties: false
+                        }
+                    ],
+                    additionalItems: false
+                },
+                {
+                    type: "array",
+                    items: [
+                        {
+                            enum: ["smart", "allow-null"]
+                        }
+                    ],
+                    additionalItems: false
+                }
+            ]
+        },
+
+        fixable: "code",
+
+        messages: {
+            unexpected: "Expected '{{expectedOperator}}' and instead saw '{{actualOperator}}'."
+        }
+    },
+
+    create(context) {
+        const config = context.options[0] || "always";
+        const options = context.options[1] || {};
+        const sourceCode = context.sourceCode;
+
+        const nullOption = (config === "always")
+            ? options.null || "always"
+            : "ignore";
+        const enforceRuleForNull = (nullOption === "always");
+        const enforceInverseRuleForNull = (nullOption === "never");
+
+        /**
+         * Checks if an expression is a typeof expression
+         * @param {ASTNode} node The node to check
+         * @returns {boolean} if the node is a typeof expression
+         */
+        function isTypeOf(node) {
+            return node.type === "UnaryExpression" && node.operator === "typeof";
+        }
+
+        /**
+         * Checks if either operand of a binary expression is a typeof operation
+         * @param {ASTNode} node The node to check
+         * @returns {boolean} if one of the operands is typeof
+         * @private
+         */
+        function isTypeOfBinary(node) {
+            return isTypeOf(node.left) || isTypeOf(node.right);
+        }
+
+        /**
+         * Checks if operands are literals of the same type (via typeof)
+         * @param {ASTNode} node The node to check
+         * @returns {boolean} if operands are of same type
+         * @private
+         */
+        function areLiteralsAndSameType(node) {
+            return node.left.type === "Literal" && node.right.type === "Literal" &&
+                    typeof node.left.value === typeof node.right.value;
+        }
+
+        /**
+         * Checks if one of the operands is a literal null
+         * @param {ASTNode} node The node to check
+         * @returns {boolean} if operands are null
+         * @private
+         */
+        function isNullCheck(node) {
+            return astUtils.isNullLiteral(node.right) || astUtils.isNullLiteral(node.left);
+        }
+
+        /**
+         * Reports a message for this rule.
+         * @param {ASTNode} node The binary expression node that was checked
+         * @param {string} expectedOperator The operator that was expected (either '==', '!=', '===', or '!==')
+         * @returns {void}
+         * @private
+         */
+        function report(node, expectedOperator) {
+            const operatorToken = sourceCode.getFirstTokenBetween(
+                node.left,
+                node.right,
+                token => token.value === node.operator
+            );
+
+            context.report({
+                node,
+                loc: operatorToken.loc,
+                messageId: "unexpected",
+                data: { expectedOperator, actualOperator: node.operator },
+                fix(fixer) {
+
+                    // If the comparison is a `typeof` comparison or both sides are literals with the same type, then it's safe to fix.
+                    if (isTypeOfBinary(node) || areLiteralsAndSameType(node)) {
+                        return fixer.replaceText(operatorToken, expectedOperator);
+                    }
+                    return null;
+                }
+            });
+        }
+
+        return {
+            BinaryExpression(node) {
+                const isNull = isNullCheck(node);
+
+                if (node.operator !== "==" && node.operator !== "!=") {
+                    if (enforceInverseRuleForNull && isNull) {
+                        report(node, node.operator.slice(0, -1));
+                    }
+                    return;
+                }
+
+                if (config === "smart" && (isTypeOfBinary(node) ||
+                        areLiteralsAndSameType(node) || isNull)) {
+                    return;
+                }
+
+                if (!enforceRuleForNull && isNull) {
+                    return;
+                }
+
+                report(node, `${node.operator}=`);
+            }
+        };
+
+    }
+};