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+/**
+ * @fileoverview Rule to prevent duplicate keys in JSON.
+ * @author Nicholas C. Zakas
+ */
+//-----------------------------------------------------------------------------
+// Imports
+//-----------------------------------------------------------------------------
+import { getKey, getRawKey } from "../util.js";
+//-----------------------------------------------------------------------------
+// Type Definitions
+//-----------------------------------------------------------------------------
+/**
+ * @import { MemberNode } from "@humanwhocodes/momoa";
+ * @import { JSONRuleDefinition } from "../types.js";
+ * @typedef {"duplicateKey"} NoDuplicateKeysMessageIds
+ * @typedef {JSONRuleDefinition<{ MessageIds: NoDuplicateKeysMessageIds }>} NoDuplicateKeysRuleDefinition
+ */
+//-----------------------------------------------------------------------------
+// Rule Definition
+//-----------------------------------------------------------------------------
+/** @type {NoDuplicateKeysRuleDefinition} */
+const rule = {
+    meta: {
+        type: "problem",
+        languages: ["json/json", "json/jsonc", "json/json5"],
+        docs: {
+            recommended: true,
+            description: "Disallow duplicate keys in JSON objects",
+            dialects: ["JSON", "JSONC", "JSON5"],
+            url: "https://github.com/eslint/json/tree/main/docs/rules/no-duplicate-keys.md",
+        },
+        messages: {
+            duplicateKey: 'Duplicate key "{{key}}" found.',
+        },
+    },
+    create(context) {
+        /** @type {Array<Map<string, MemberNode>|undefined>} */
+        const objectKeys = [];
+        /** @type {Map<string, MemberNode>|undefined} */
+        let keys;
+        return {
+            Object() {
+                objectKeys.push(keys);
+                keys = new Map();
+            },
+            Member(node) {
+                const key = getKey(node);
+                const rawKey = getRawKey(node, context.sourceCode);
+                if (keys.has(key)) {
+                    context.report({
+                        loc: node.name.loc,
+                        messageId: "duplicateKey",
+                        data: {
+                            key: rawKey,
+                        },
+                    });
+                }
+                else {
+                    keys.set(key, node);
+                }
+            },
+            "Object:exit"() {
+                keys = objectKeys.pop();
+            },
+        };
+    },
+};
+export default rule;