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qwen/nodejs/node_modules/eslint/lib/rules/no-unused-labels.js

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+/**
+ * @fileoverview Rule to disallow unused labels.
+ * @author Toru Nagashima
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "Disallow unused labels",
+            recommended: true,
+            url: "https://eslint.org/docs/latest/rules/no-unused-labels"
+        },
+
+        schema: [],
+
+        fixable: "code",
+
+        messages: {
+            unused: "'{{name}}:' is defined but never used."
+        }
+    },
+
+    create(context) {
+        const sourceCode = context.sourceCode;
+        let scopeInfo = null;
+
+        /**
+         * Adds a scope info to the stack.
+         * @param {ASTNode} node A node to add. This is a LabeledStatement.
+         * @returns {void}
+         */
+        function enterLabeledScope(node) {
+            scopeInfo = {
+                label: node.label.name,
+                used: false,
+                upper: scopeInfo
+            };
+        }
+
+        /**
+         * Checks if a `LabeledStatement` node is fixable.
+         * For a node to be fixable, there must be no comments between the label and the body.
+         * Furthermore, is must be possible to remove the label without turning the body statement into a
+         * directive after other fixes are applied.
+         * @param {ASTNode} node The node to evaluate.
+         * @returns {boolean} Whether or not the node is fixable.
+         */
+        function isFixable(node) {
+
+            /*
+             * Only perform a fix if there are no comments between the label and the body. This will be the case
+             * when there is exactly one token/comment (the ":") between the label and the body.
+             */
+            if (sourceCode.getTokenAfter(node.label, { includeComments: true }) !==
+                sourceCode.getTokenBefore(node.body, { includeComments: true })) {
+                return false;
+            }
+
+            // Looking for the node's deepest ancestor which is not a `LabeledStatement`.
+            let ancestor = node.parent;
+
+            while (ancestor.type === "LabeledStatement") {
+                ancestor = ancestor.parent;
+            }
+
+            if (ancestor.type === "Program" ||
+                (ancestor.type === "BlockStatement" && astUtils.isFunction(ancestor.parent))) {
+                const { body } = node;
+
+                if (body.type === "ExpressionStatement" &&
+                    ((body.expression.type === "Literal" && typeof body.expression.value === "string") ||
+                    astUtils.isStaticTemplateLiteral(body.expression))) {
+                    return false; // potential directive
+                }
+            }
+            return true;
+        }
+
+        /**
+         * Removes the top of the stack.
+         * At the same time, this reports the label if it's never used.
+         * @param {ASTNode} node A node to report. This is a LabeledStatement.
+         * @returns {void}
+         */
+        function exitLabeledScope(node) {
+            if (!scopeInfo.used) {
+                context.report({
+                    node: node.label,
+                    messageId: "unused",
+                    data: node.label,
+                    fix: isFixable(node) ? fixer => fixer.removeRange([node.range[0], node.body.range[0]]) : null
+                });
+            }
+
+            scopeInfo = scopeInfo.upper;
+        }
+
+        /**
+         * Marks the label of a given node as used.
+         * @param {ASTNode} node A node to mark. This is a BreakStatement or
+         *      ContinueStatement.
+         * @returns {void}
+         */
+        function markAsUsed(node) {
+            if (!node.label) {
+                return;
+            }
+
+            const label = node.label.name;
+            let info = scopeInfo;
+
+            while (info) {
+                if (info.label === label) {
+                    info.used = true;
+                    break;
+                }
+                info = info.upper;
+            }
+        }
+
+        return {
+            LabeledStatement: enterLabeledScope,
+            "LabeledStatement:exit": exitLabeledScope,
+            BreakStatement: markAsUsed,
+            ContinueStatement: markAsUsed
+        };
+    }
+};