fix: sqlalchemy server version info without request

lib/dl_sqlalchemy_postgres/dl_sqlalchemy_postgres/base.py

@@ -122,6 +122,17 @@ def __init__(self, enforce_collate=None, **kwargs):
     type_compiler = BICustomPGTypeCompiler
     statement_compiler = BIPGCompilerBasic
     ischema_names = bi_pg_ischema_names
+    forced_server_version_string: str | None = None
+
+    def connect(self, *cargs, **cparams):
+        self.forced_server_version_string = cparams.pop("server_version", self.forced_server_version_string)
+        return super().connect(*cargs, **cparams)
+
+    def _get_server_version_info(self, connection) -> tuple[int, ...]:
+        if self.forced_server_version_string is not None:
+            return tuple(int(part) for part in self.forced_server_version_string.split("."))
+
+        return super()._get_server_version_info(connection)
 
 
 class BIPGDialect(BIPGDialectBasic):

lib/dl_sqlalchemy_postgres/dl_sqlalchemy_postgres_tests/unit/test_server_version.py

@@ -0,0 +1,16 @@
+import sqlalchemy
+import sqlalchemy.orm as sqlalchemy_orm
+
+
+SERVER_VERSION_INFO = (123, 45, 67, 89)
+SERVER_VERSION = ".".join(map(str, SERVER_VERSION_INFO))
+
+
+def test_server_version(engine_url: str):
+    engine = sqlalchemy.create_engine(engine_url, connect_args=dict(server_version=SERVER_VERSION))
+    session_maker = sqlalchemy_orm.sessionmaker(bind=engine)
+    engine_session = session_maker()
+    # Connection and version get initialized on first query:
+    engine_session.scalar("select 1")
+    ver = engine_session.get_bind().dialect.server_version_info
+    assert ver == SERVER_VERSION_INFO