From bc88aa57f55b2c3605cbb9c66f2e66daa695c20c Mon Sep 17 00:00:00 2001
From: Siddharth Agrawal <siddag@google.com>
Date: Mon, 30 Oct 2023 20:25:42 -0700
Subject: [PATCH] feat: add support for proto3 optional tag (#2295)

---
 .../bigquery/storage/v1/ProtoSchemaConverter.java     | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/ProtoSchemaConverter.java b/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/ProtoSchemaConverter.java
index c55d4181a5..16e8e3425d 100644
--- a/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/ProtoSchemaConverter.java
+++ b/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/ProtoSchemaConverter.java
@@ -102,6 +102,17 @@ private static ProtoSchema convertInternal(
           enumTypes.add(enumFullName);
         }
       }
+      // The protobuf payload will be decoded as proto2 on the server side. The schema is also
+      // specified as proto2. Hence we must clear proto3-only features. This works since proto2 and
+      // proto3 are binary-compatible.
+      if (resultField.hasProto3Optional()) {
+        // Clear proto3-only features
+        resultField.clearProto3Optional();
+      }
+      if (resultField.hasOneofIndex()) {
+        // Clear proto3-only features
+        resultField.clearOneofIndex();
+      }
       resultProto.addField(resultField);
     }
     structTypes.add(protoFullName);