Fix bug in device ID collision handling, add tests (#45010)

Summary:
Pull Request resolved: #45010

D46482492 added logic for handing off state across "device" connections that have the same ID. This logic currently has no test coverage. It also contains a bug whereby the new device's pages are removed from the target listing endpoint (`/json`) when the *old* device's socket is closed.

This diff adds tests and fixes the bug.

Changelog: [General][Fixed] inspector-proxy no longer accidentally detaches connected devices.

## Next steps

It seems that the device ID handoff logic exists to paper over a deeper problem with the inspector proxy protocol (or its implementation in React Native): The React Native runtime should not routinely be creating new "device" connections without tearing down previous ones.

In followup diffs, I'll explore changing this behaviour for Fusebox, based on the new test coverage.

Reviewed By: robhogan

Differential Revision: D51013056

fbshipit-source-id: e0c17678cc747366a3b75cef18ca2a722fc93acd

Author: motiz88

packages/dev-middleware/src/__tests__/InspectorDeviceUtils.js

@@ -20,6 +20,7 @@ import type {
   WrappedEvent,
 } from '../inspector-proxy/types';
 
+import nullthrows from 'nullthrows';
 import WebSocket from 'ws';
 
 export class DeviceAgent {
@@ -82,6 +83,11 @@ export class DeviceAgent {
       },
     });
   }
+
+  // $FlowIgnore[unsafe-getters-setters]
+  get socket(): WebSocket {
+    return nullthrows(this.#ws);
+  }
 }
 
 export class DeviceMock extends DeviceAgent {

packages/dev-middleware/src/__tests__/InspectorProtocolUtils.js

@@ -126,12 +126,15 @@ export async function createAndConnectTarget(
   }>,
   signal: AbortSignal,
   page: PageFromDevice,
+  deviceId: ?string = null,
 ): Promise<{device: DeviceMock, debugger_: DebuggerMock}> {
   let device;
   let debugger_;
   try {
     device = await createDeviceMock(
-      `${serverRef.serverBaseWsUrl}/inspector/device?device=device&name=foo&app=bar`,
+      `${serverRef.serverBaseWsUrl}/inspector/device?device=${
+        deviceId ?? 'device' + Date.now()
+      }&name=foo&app=bar`,
       signal,
     );
     device.getPages.mockImplementation(() => [page]);

packages/dev-middleware/src/__tests__/InspectorProxyCdpTransport-test.js

@@ -9,7 +9,10 @@
  * @oncall react_native
  */
 
-import type {PageDescription} from '../inspector-proxy/types';
+import type {
+  JsonPagesListResponse,
+  PageDescription,
+} from '../inspector-proxy/types';
 
 import {fetchJson} from './FetchUtils';
 import {createDebuggerMock} from './InspectorDebuggerUtils';
@@ -51,7 +54,7 @@ describe.each(['HTTP', 'HTTPS'])(
           },
         ]);
 
-        let pageList: Array<PageDescription> = [];
+        let pageList: JsonPagesListResponse = [];
         await until(async () => {
           pageList = (await fetchJson(
             `${serverRef.serverBaseUrl}/json`,