fix: Empty sync message causes error in client MessageReceiver (#174)

Author: tommoor

packages/provider/src/MessageReceiver.ts

@@ -43,19 +43,15 @@ export class MessageReceiver {
 
     message.writeVarUint(MessageType.Sync)
 
-    try {
-      const syncMessageType = readSyncMessage(
-        message.decoder,
-        message.encoder,
-        provider.document,
-        provider,
-      )
-
-      if (emitSynced && syncMessageType === messageYjsSyncStep2) {
-        provider.synced = true
-      }
-    } catch (e) {
-      // TODO: That shouldn’t happen … but it does. Remove the try/catch and run the tests.
+    const syncMessageType = readSyncMessage(
+      message.decoder,
+      message.encoder,
+      provider.document,
+      provider,
+    )
+
+    if (emitSynced && syncMessageType === messageYjsSyncStep2) {
+      provider.synced = true
     }
   }
 

packages/server/src/IncomingMessage.ts

@@ -9,6 +9,7 @@ import {
   Encoder,
   toUint8Array,
   writeVarUint,
+  length,
 } from 'lib0/encoding'
 import { MessageType } from './types'
 
@@ -47,4 +48,8 @@ export class IncomingMessage {
   writeVarUint(type: MessageType) {
     writeVarUint(this.encoder, type)
   }
+
+  get length(): number {
+    return length(this.encoder)
+  }
 }

packages/server/src/MessageReceiver.ts

@@ -28,7 +28,10 @@ export class MessageReceiver {
       case MessageType.Sync:
         message.writeVarUint(MessageType.Sync)
         this.readSyncMessage(message, connection)
-        connection.send(message.toUint8Array())
+
+        if (message.length > 1) {
+          connection.send(message.toUint8Array())
+        }
 
         break
       case MessageType.Awareness: