Recover from malformed JSON

Summary: Following up on D34787674 (f85def32fb).

Reviewed By: aigoncharov

Differential Revision: D34930249

fbshipit-source-id: f209a638c1281957fd2b03b6fc50389bd98bc5f6

desktop/flipper-common/src/transport.tsx

@@ -14,6 +14,11 @@ type GenericWebSocketMessage<E = string, T = unknown> = {
   payload: T;
 };
 
+export type GenericWebSocketError = GenericWebSocketMessage<
+  'error',
+  {message: string}
+>;
+
 export type ExecWebSocketMessage = GenericWebSocketMessage<
   'exec',
   {

desktop/flipper-server/src/startSocketServer.tsx

@@ -13,6 +13,7 @@ import {
   ExecResponseWebSocketMessage,
   ExecResponseErrorWebSocketMessage,
   ServerEventWebSocketMessage,
+  GenericWebSocketError,
 } from 'flipper-common';
 import {FlipperServerImpl} from 'flipper-server-core';
 import {WebSocketServer} from 'ws';
@@ -42,9 +43,23 @@ export function startSocketServer(
     flipperServer.onAny(onServerEvent);
 
     client.on('message', (data) => {
-      const {event, payload} = JSON.parse(
-        data.toString(),
-      ) as ClientWebSocketMessage;
+      let [event, payload]: [event: string | null, payload: any | null] = [
+        null,
+        null,
+      ];
+      try {
+        ({event, payload} = JSON.parse(
+          data.toString(),
+        ) as ClientWebSocketMessage);
+      } catch (err) {
+        console.warn('flipperServer -> onMessage: failed to parse JSON', err);
+        const response: GenericWebSocketError = {
+          event: 'error',
+          payload: {message: `Failed to parse JSON request: ${err}`},
+        };
+        client.send(JSON.stringify(response));
+        return;
+      }
 
       switch (event) {
         case 'exec': {