From 83bccf9c49056de775324e1c580391b59525397f Mon Sep 17 00:00:00 2001
From: Boyuan Zhang <boyuanz@google.com>
Date: Mon, 24 May 2021 11:01:59 -0700
Subject: [PATCH] [BEAM-12384] Infer typeDescriptor from coder if
 typeDescriptor is not set explicitly.

---
 .../main/java/org/apache/beam/sdk/values/PCollection.java | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sdks/java/core/src/main/java/org/apache/beam/sdk/values/PCollection.java b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/PCollection.java
index a637951ff1d8..5e85eb8c4adb 100644
--- a/sdks/java/core/src/main/java/org/apache/beam/sdk/values/PCollection.java
+++ b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/PCollection.java
@@ -124,7 +124,13 @@ public void finishSpecifying(PInput input, PTransform<?, ?> transform) {
    * override this to enable better {@code Coder} inference.
    */
   public @Nullable TypeDescriptor<T> getTypeDescriptor() {
-    return typeDescriptor;
+    if (typeDescriptor != null) {
+      return typeDescriptor;
+    }
+    if (coderOrFailure.coder != null) {
+      return coderOrFailure.coder.getEncodedTypeDescriptor();
+    }
+    return null;
   }
 
   /**