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qwen/nodejs/node_modules/eslint/lib/rules/no-lone-blocks.js

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+/**
+ * @fileoverview Rule to flag blocks with no reason to exist
+ * @author Brandon Mills
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "Disallow unnecessary nested blocks",
+            recommended: false,
+            url: "https://eslint.org/docs/latest/rules/no-lone-blocks"
+        },
+
+        schema: [],
+
+        messages: {
+            redundantBlock: "Block is redundant.",
+            redundantNestedBlock: "Nested block is redundant."
+        }
+    },
+
+    create(context) {
+
+        // A stack of lone blocks to be checked for block-level bindings
+        const loneBlocks = [];
+        let ruleDef;
+        const sourceCode = context.sourceCode;
+
+        /**
+         * Reports a node as invalid.
+         * @param {ASTNode} node The node to be reported.
+         * @returns {void}
+         */
+        function report(node) {
+            const messageId = node.parent.type === "BlockStatement" || node.parent.type === "StaticBlock"
+                ? "redundantNestedBlock"
+                : "redundantBlock";
+
+            context.report({
+                node,
+                messageId
+            });
+        }
+
+        /**
+         * Checks for any occurrence of a BlockStatement in a place where lists of statements can appear
+         * @param {ASTNode} node The node to check
+         * @returns {boolean} True if the node is a lone block.
+         */
+        function isLoneBlock(node) {
+            return node.parent.type === "BlockStatement" ||
+                node.parent.type === "StaticBlock" ||
+                node.parent.type === "Program" ||
+
+                // Don't report blocks in switch cases if the block is the only statement of the case.
+                node.parent.type === "SwitchCase" && !(node.parent.consequent[0] === node && node.parent.consequent.length === 1);
+        }
+
+        /**
+         * Checks the enclosing block of the current node for block-level bindings,
+         * and "marks it" as valid if any.
+         * @param {ASTNode} node The current node to check.
+         * @returns {void}
+         */
+        function markLoneBlock(node) {
+            if (loneBlocks.length === 0) {
+                return;
+            }
+
+            const block = node.parent;
+
+            if (loneBlocks[loneBlocks.length - 1] === block) {
+                loneBlocks.pop();
+            }
+        }
+
+        // Default rule definition: report all lone blocks
+        ruleDef = {
+            BlockStatement(node) {
+                if (isLoneBlock(node)) {
+                    report(node);
+                }
+            }
+        };
+
+        // ES6: report blocks without block-level bindings, or that's only child of another block
+        if (context.languageOptions.ecmaVersion >= 2015) {
+            ruleDef = {
+                BlockStatement(node) {
+                    if (isLoneBlock(node)) {
+                        loneBlocks.push(node);
+                    }
+                },
+                "BlockStatement:exit"(node) {
+                    if (loneBlocks.length > 0 && loneBlocks[loneBlocks.length - 1] === node) {
+                        loneBlocks.pop();
+                        report(node);
+                    } else if (
+                        (
+                            node.parent.type === "BlockStatement" ||
+                            node.parent.type === "StaticBlock"
+                        ) &&
+                        node.parent.body.length === 1
+                    ) {
+                        report(node);
+                    }
+                }
+            };
+
+            ruleDef.VariableDeclaration = function(node) {
+                if (node.kind === "let" || node.kind === "const") {
+                    markLoneBlock(node);
+                }
+            };
+
+            ruleDef.FunctionDeclaration = function(node) {
+                if (sourceCode.getScope(node).isStrict) {
+                    markLoneBlock(node);
+                }
+            };
+
+            ruleDef.ClassDeclaration = markLoneBlock;
+        }
+
+        return ruleDef;
+    }
+};