chore(spanner): Issue1178# [spanner_dbapi] While running a query that…

… contains just comment, it causes an IndexError exception (#1181)

- returned ProgrammingError - Invalid statement

google/cloud/spanner_dbapi/cursor.py

@@ -251,6 +251,9 @@ def _execute(self, sql, args=None, call_from_execute_many=False):
         exception = None
         try:
             self._parsed_statement = parse_utils.classify_statement(sql, args)
+            if self._parsed_statement is None:
+                raise ProgrammingError("Invalid Statement.")
+
             if self._parsed_statement.statement_type == StatementType.CLIENT_SIDE:
                 self._result_set = client_side_statement_executor.execute(
                     self, self._parsed_statement

google/cloud/spanner_dbapi/parse_utils.py

@@ -226,6 +226,8 @@ def classify_statement(query, args=None):
     # PostgreSQL dollar quoted comments are not
     # supported and will not be stripped.
     query = sqlparse.format(query, strip_comments=True).strip()
+    if query == "":
+        return None
     parsed_statement: ParsedStatement = client_side_statement_parser.parse_stmt(query)
     if parsed_statement is not None:
         return parsed_statement

tests/system/test_dbapi.py

@@ -1598,3 +1598,7 @@ def test_list_tables(self, include_views):
             assert "contacts_emails" in table_names
         else:  # if not include_views:
             assert "contacts_emails" not in table_names
+
+    def test_invalid_statement_error(self):
+        with pytest.raises(ProgrammingError):
+            self._cursor.execute("-- comment only")