chore: import upstream snapshot with attribution

packages/core/src/v3/locals/index.ts

@@ -0,0 +1,45 @@
+const API_NAME = "locals";
+
+import { getGlobal, registerGlobal, unregisterGlobal } from "../utils/globals.js";
+import { NoopLocalsManager } from "./manager.js";
+import { type LocalsKey, type LocalsManager } from "./types.js";
+
+const NOOP_LOCALS_MANAGER = new NoopLocalsManager();
+
+export class LocalsAPI implements LocalsManager {
+  private static _instance?: LocalsAPI;
+
+  private constructor() {}
+
+  public static getInstance(): LocalsAPI {
+    if (!this._instance) {
+      this._instance = new LocalsAPI();
+    }
+
+    return this._instance;
+  }
+
+  public setGlobalLocalsManager(localsManager: LocalsManager): boolean {
+    return registerGlobal(API_NAME, localsManager);
+  }
+
+  public disable() {
+    unregisterGlobal(API_NAME);
+  }
+
+  public createLocal<T>(id: string): LocalsKey<T> {
+    return this.#getManager().createLocal(id);
+  }
+
+  public getLocal<T>(key: LocalsKey<T>): T | undefined {
+    return this.#getManager().getLocal(key);
+  }
+
+  public setLocal<T>(key: LocalsKey<T>, value: T): void {
+    return this.#getManager().setLocal(key, value);
+  }
+
+  #getManager(): LocalsManager {
+    return getGlobal(API_NAME) ?? NOOP_LOCALS_MANAGER;
+  }
+}