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qwen/nodejs/node_modules/eslint/lib/rules/vars-on-top.js

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+/**
+ * @fileoverview Rule to enforce var declarations are only at the top of a function.
+ * @author Danny Fritz
+ * @author Gyandeep Singh
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "Require `var` declarations be placed at the top of their containing scope",
+            recommended: false,
+            url: "https://eslint.org/docs/latest/rules/vars-on-top"
+        },
+
+        schema: [],
+        messages: {
+            top: "All 'var' declarations must be at the top of the function scope."
+        }
+    },
+
+    create(context) {
+
+        //--------------------------------------------------------------------------
+        // Helpers
+        //--------------------------------------------------------------------------
+
+        /**
+         * Has AST suggesting a directive.
+         * @param {ASTNode} node any node
+         * @returns {boolean} whether the given node structurally represents a directive
+         */
+        function looksLikeDirective(node) {
+            return node.type === "ExpressionStatement" &&
+                node.expression.type === "Literal" && typeof node.expression.value === "string";
+        }
+
+        /**
+         * Check to see if its a ES6 import declaration
+         * @param {ASTNode} node any node
+         * @returns {boolean} whether the given node represents a import declaration
+         */
+        function looksLikeImport(node) {
+            return node.type === "ImportDeclaration" || node.type === "ImportSpecifier" ||
+                node.type === "ImportDefaultSpecifier" || node.type === "ImportNamespaceSpecifier";
+        }
+
+        /**
+         * Checks whether a given node is a variable declaration or not.
+         * @param {ASTNode} node any node
+         * @returns {boolean} `true` if the node is a variable declaration.
+         */
+        function isVariableDeclaration(node) {
+            return (
+                node.type === "VariableDeclaration" ||
+                (
+                    node.type === "ExportNamedDeclaration" &&
+                    node.declaration &&
+                    node.declaration.type === "VariableDeclaration"
+                )
+            );
+        }
+
+        /**
+         * Checks whether this variable is on top of the block body
+         * @param {ASTNode} node The node to check
+         * @param {ASTNode[]} statements collection of ASTNodes for the parent node block
+         * @returns {boolean} True if var is on top otherwise false
+         */
+        function isVarOnTop(node, statements) {
+            const l = statements.length;
+            let i = 0;
+
+            // Skip over directives and imports. Static blocks don't have either.
+            if (node.parent.type !== "StaticBlock") {
+                for (; i < l; ++i) {
+                    if (!looksLikeDirective(statements[i]) && !looksLikeImport(statements[i])) {
+                        break;
+                    }
+                }
+            }
+
+            for (; i < l; ++i) {
+                if (!isVariableDeclaration(statements[i])) {
+                    return false;
+                }
+                if (statements[i] === node) {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        /**
+         * Checks whether variable is on top at the global level
+         * @param {ASTNode} node The node to check
+         * @param {ASTNode} parent Parent of the node
+         * @returns {void}
+         */
+        function globalVarCheck(node, parent) {
+            if (!isVarOnTop(node, parent.body)) {
+                context.report({ node, messageId: "top" });
+            }
+        }
+
+        /**
+         * Checks whether variable is on top at functional block scope level
+         * @param {ASTNode} node The node to check
+         * @returns {void}
+         */
+        function blockScopeVarCheck(node) {
+            const { parent } = node;
+
+            if (
+                parent.type === "BlockStatement" &&
+                /Function/u.test(parent.parent.type) &&
+                isVarOnTop(node, parent.body)
+            ) {
+                return;
+            }
+
+            if (
+                parent.type === "StaticBlock" &&
+                isVarOnTop(node, parent.body)
+            ) {
+                return;
+            }
+
+            context.report({ node, messageId: "top" });
+        }
+
+        //--------------------------------------------------------------------------
+        // Public API
+        //--------------------------------------------------------------------------
+
+        return {
+            "VariableDeclaration[kind='var']"(node) {
+                if (node.parent.type === "ExportNamedDeclaration") {
+                    globalVarCheck(node.parent, node.parent.parent);
+                } else if (node.parent.type === "Program") {
+                    globalVarCheck(node, node.parent);
+                } else {
+                    blockScopeVarCheck(node);
+                }
+            }
+        };
+
+    }
+};