[GitHub] [beam] TheNeuralBit commented on a change in pull request #11314: [BEAM-9562] Send Timers over Data Channel as Elements

[GitBox <gi...@apache.org>]

TheNeuralBit commented on a change in pull request #11314: [BEAM-9562] Send Timers over Data Channel as Elements
URL: https://github.com/apache/beam/pull/11314#discussion_r405831920
 
 

 ##########
 File path: runners/core-construction-java/src/main/java/org/apache/beam/runners/core/construction/ParDoTranslation.java
 ##########
 @@ -257,6 +230,19 @@ public static ParDoPayload translateParDo(
       restrictionCoderId = "";
     }
 
+    Coder<BoundedWindow> windowCoder =
+        (Coder<BoundedWindow>) mainInput.getWindowingStrategy().getWindowFn().windowCoder();
+    Coder<?> keyCoder;
+    if (signature.usesState() || signature.usesTimers()) {
+      checkArgument(
+          mainInput.getCoder() instanceof KvCoder,
+          "DoFn's that use state or timers must have an input PCollection with a KvCoder but received %s",
+          mainInput.getCoder());
 
 Review comment:
   Just curious: did we not have this check before, and just failed when attempting to cast to KVCoder  (in the removed block from `translate` above)?

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