fix(client-presence): LatestValueManager with array comes across as object (#23662)

## Bug Description
[ADO Bug
29110](https://dev.azure.com/fluidframework/internal/_workitems/edit/29110)

Using an array (at least using `string[]`) as the type for `Latest`
(`LatestValueManager`) appears to rehydrate as object rather than array.
Example result:
```JSON
{
   "0": "foo"
}
```

Repro branch:
https://github.com/jason-ha/FluidExamples/tree/presence_Latest_array
Repro: connect two clients; make selection in one
Expected: selection shows in other
Actual: runtime error `indexOf` is not a member of ...

## Solution
When we create a LatestValueManager with an`initialValue`, we make a
shallow copy by doing `{ ..initialValue}`. So if `initialValue` is an
array we're transforming it into an object. To avoid this we can check
if it's an array first and maintain array.
Was able to solve the repro with this fix.

Author: WillieHabi

packages/common/core-utils/src/index.ts

@@ -17,6 +17,7 @@ export { Lazy, LazyPromise } from "./lazy.js";
 export type { PromiseCacheExpiry, PromiseCacheOptions } from "./promiseCache.js";
 export { PromiseCache } from "./promiseCache.js";
 export { Deferred } from "./promises.js";
+export { shallowCloneObject } from "./shallowClone.js";
 export type { IPromiseTimer, IPromiseTimerResult, ITimer } from "./timer.js";
 export { PromiseTimer, setLongTimeout, Timer } from "./timer.js";
 export { unreachableCase } from "./unreachable.js";

packages/common/core-utils/src/shallowClone.ts

@@ -0,0 +1,18 @@
+/*!
+ * Copyright (c) Microsoft Corporation and contributors. All rights reserved.
+ * Licensed under the MIT License.
+ */
+
+/**
+ * Shallow clone an object.
+ *
+ * @param value - The object to clone
+ * @returns A shallow clone of the input value
+ * @internal
+ */
+export function shallowCloneObject<T extends object>(value: T): T {
+	if (Array.isArray(value)) {
+		return [...value] as T;
+	}
+	return { ...value };
+}

packages/framework/presence/src/latestValueManager.ts

@@ -5,6 +5,7 @@
 
 import { createEmitter } from "@fluid-internal/client-utils";
 import type { Listenable } from "@fluidframework/core-interfaces";
+import { shallowCloneObject } from "@fluidframework/core-utils/internal";
 
 import type { BroadcastControls, BroadcastControlSettings } from "./broadcastControls.js";
 import { OptionalBroadcastControl } from "./broadcastControls.js";
@@ -178,7 +179,7 @@ export function Latest<T extends object, Key extends string = string>(
 	const value: InternalTypes.ValueRequiredState<T> = {
 		rev: 0,
 		timestamp: Date.now(),
-		value: { ...initialValue },
+		value: shallowCloneObject(initialValue),
 	};
 	const factory = (
 		key: Key,

packages/framework/presence/src/test/latestValueManager.spec.ts

@@ -3,7 +3,12 @@
  * Licensed under the MIT License.
  */
 
+import { strict as assert } from "node:assert";
+
+import { createPresenceManager } from "../presenceManager.js";
+
 import { addControlsTests } from "./broadcastControlsTests.js";
+import { MockEphemeralRuntime } from "./mockEphemeralRuntime.js";
 
 import type {
 	BroadcastControlSettings,
@@ -12,12 +17,14 @@ import type {
 } from "@fluidframework/presence/alpha";
 import { Latest } from "@fluidframework/presence/alpha";
 
+const testWorkspaceName = "name:testWorkspaceA";
+
 // eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 function createLatestManager(
 	presence: IPresence,
 	valueControlSettings?: BroadcastControlSettings,
 ) {
-	const states = presence.getStates("name:testWorkspaceA", {
+	const states = presence.getStates(testWorkspaceName, {
 		camera: Latest({ x: 0, y: 0, z: 0 }, valueControlSettings),
 	});
 	return states.props.camera;
@@ -30,6 +37,42 @@ describe("Presence", () => {
 		 */
 		it("API use compiles", () => {});
 
+		describe("when initialized", () => {
+			let presence: IPresence;
+
+			beforeEach(() => {
+				presence = createPresenceManager(new MockEphemeralRuntime());
+			});
+
+			it("can set and get empty object as initial value", () => {
+				const states = presence.getStates(testWorkspaceName, {
+					obj: Latest({}),
+				});
+				assert.deepStrictEqual(states.props.obj.local, {});
+			});
+
+			it("can set and get object with properties as initial value", () => {
+				const states = presence.getStates(testWorkspaceName, {
+					obj: Latest({ x: 0, y: 0, z: 0 }),
+				});
+				assert.deepStrictEqual(states.props.obj.local, { x: 0, y: 0, z: 0 });
+			});
+
+			it("can set and get empty array as initial value", () => {
+				const states = presence.getStates(testWorkspaceName, {
+					arr: Latest([]),
+				});
+				assert.deepStrictEqual(states.props.arr.local, []);
+			});
+
+			it("can set and get array with elements as initial value", () => {
+				const states = presence.getStates(testWorkspaceName, {
+					arr: Latest([1, 2, 3]),
+				});
+				assert.deepStrictEqual(states.props.arr.local, [1, 2, 3]);
+			});
+		});
+
 		addControlsTests(createLatestManager);
 	});
 });