fix: E2E tracing metadata append issue (#1357)

Author: surbhigarg92

google/cloud/spanner_v1/_helpers.py

@@ -603,7 +603,7 @@ def _metadata_with_span_context(metadata: List[Tuple[str, str]], **kw) -> None:
     Returns:
         None
     """
-    if HAS_OPENTELEMETRY_INSTALLED:
+    if HAS_OPENTELEMETRY_INSTALLED and metadata is not None:
         metadata.append(("x-goog-spanner-end-to-end-tracing", "true"))
         inject(setter=OpenTelemetryContextSetter(), carrier=metadata)
 

tests/unit/test_database.py

@@ -1401,7 +1401,7 @@ def test_run_in_transaction_wo_args(self):
         import datetime
 
         NOW = datetime.datetime.now()
-        client = _Client()
+        client = _Client(observability_options=dict(enable_end_to_end_tracing=True))
         instance = _Instance(self.INSTANCE_NAME, client=client)
         pool = _Pool()
         session = _Session()
@@ -3121,6 +3121,7 @@ def __init__(
         route_to_leader_enabled=True,
         directed_read_options=None,
         default_transaction_options=DefaultTransactionOptions(),
+        observability_options=None,
     ):
         from google.cloud.spanner_v1 import ExecuteSqlRequest
 
@@ -3135,6 +3136,7 @@ def __init__(
         self.route_to_leader_enabled = route_to_leader_enabled
         self.directed_read_options = directed_read_options
         self.default_transaction_options = default_transaction_options
+        self.observability_options = observability_options
 
 
 class _Instance(object):