fix(grpc): Return proper metadata object instead of list in… (#3205)

* fix(grpc): Return propagate proper metadata object instead of list in client interceptor

Fixes #2509

* fix(grpc): Transform metadata into Metadata object in case it's a tuple

Up until version 1.65.0 of grpcio, the metadata was not guaranteed to
arrive as the type specified in annotations but could be a tuple.
To support versions before that we check and transform it here.

* docs(grpc): Add comment about workaround

---------

Co-authored-by: Anton Pirker <[email protected]>
Co-authored-by: Daniel Szoke <[email protected]>

sentry_sdk/integrations/grpc/aio/client.py

@@ -6,6 +6,7 @@
     ClientCallDetails,
     UnaryUnaryCall,
     UnaryStreamCall,
+    Metadata,
 )
 from google.protobuf.message import Message
 
@@ -19,23 +20,19 @@ class ClientInterceptor:
     def _update_client_call_details_metadata_from_scope(
         client_call_details: ClientCallDetails,
     ) -> ClientCallDetails:
-        metadata = (
-            list(client_call_details.metadata) if client_call_details.metadata else []
-        )
+        if client_call_details.metadata is None:
+            client_call_details = client_call_details._replace(metadata=Metadata())
+        elif not isinstance(client_call_details.metadata, Metadata):
+            # This is a workaround for a GRPC bug, which was fixed in grpcio v1.60.0
+            # See https://github.com/grpc/grpc/issues/34298.
+            client_call_details = client_call_details._replace(
+                metadata=Metadata.from_tuple(client_call_details.metadata)
+            )
         for (
             key,
             value,
         ) in sentry_sdk.get_current_scope().iter_trace_propagation_headers():
-            metadata.append((key, value))
-
-        client_call_details = ClientCallDetails(
-            method=client_call_details.method,
-            timeout=client_call_details.timeout,
-            metadata=metadata,
-            credentials=client_call_details.credentials,
-            wait_for_ready=client_call_details.wait_for_ready,
-        )
-
+            client_call_details.metadata.add(key, value)
         return client_call_details