Handle empty strings in sqlcommenter (open-telemetry#3309)

* Handle empty strings

Safer check for a trailing semicolon that could handle
empty strings as well.

* Updated CHANGELOG.md

* Test for empty SQL strings in sqlcommenter

---------

Co-authored-by: Riccardo Magliocchetti <[email protected]>

Author: selcuk

CHANGELOG.md

@@ -46,6 +46,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3249](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3249))
 - `opentelemetry-instrumentation-asyncpg` Fix fallback for empty queries.
   ([#3253](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3253))
+- `opentelemetry-instrumentation` Fix a traceback in sqlcommenter when psycopg connection pooling is enabled.
+  ([#3309](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3309))
 - `opentelemetry-instrumentation-threading` Fix broken context typehints
   ([#3322](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3322))
 - `opentelemetry-instrumentation-requests` always record span status code in duration metric

instrumentation/opentelemetry-instrumentation-django/tests/test_sqlcommenter.py

@@ -146,3 +146,31 @@ def test_multiple_connection_support(self, query_wrapper):
 
         # check if query_wrapper is added to the context for 2 databases
         self.assertEqual(query_wrapper.call_count, 2)
+
+    @patch(
+        "opentelemetry.instrumentation.django.middleware.sqlcommenter_middleware._get_opentelemetry_values"
+    )
+    def test_empty_sql(self, trace_capture):
+        requests_mock = MagicMock()
+        requests_mock.resolver_match.view_name = "view"
+        requests_mock.resolver_match.route = "route"
+        requests_mock.resolver_match.app_name = "app"
+
+        trace_capture.return_value = {
+            "traceparent": "*traceparent='00-000000000000000000000000deadbeef-000000000000beef-00"
+        }
+        qw_instance = _QueryWrapper(requests_mock)
+        execute_mock_obj = MagicMock()
+        qw_instance(
+            execute_mock_obj,
+            "",
+            MagicMock("test"),
+            MagicMock("test1"),
+            MagicMock(),
+        )
+        output_sql = execute_mock_obj.call_args[0][0]
+        self.assertEqual(
+            output_sql,
+            " /*app_name='app',controller='view',route='route',traceparent='%%2Atraceparent%%3D%%2700-0000000"
+            "00000000000000000deadbeef-000000000000beef-00'*/",
+        )

opentelemetry-instrumentation/src/opentelemetry/instrumentation/sqlcommenter_utils.py

@@ -23,7 +23,7 @@ def _add_sql_comment(sql, **meta) -> str:
     meta.update(**_add_framework_tags())
     comment = _generate_sql_comment(**meta)
     sql = sql.rstrip()
-    if sql[-1] == ";":
+    if sql.endswith(";"):
         sql = sql[:-1] + comment + ";"
     else:
         sql = sql + comment