Run Gateway token renewers even if the auth token is empty. (#1340)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: ojarjur

jupyter_server/gateway/gateway_client.py

@@ -601,7 +601,7 @@ def load_connection_args(self, **kwargs):
 
         # Give token renewal a shot at renewing the token
         prev_auth_token = self.auth_token
-        if self.auth_token:
+        if self.auth_token is not None:
             try:
                 self.auth_token = self.gateway_token_renewer.get_token(
                     self.auth_header_key, self.auth_scheme, self.auth_token

tests/test_gateway.py

@@ -303,13 +303,19 @@ def test_gateway_cli_options(jp_configurable_serverapp, capsys):
     GatewayClient.clear_instance()
 
 
-@pytest.mark.parametrize("renewer_type", ["default", "custom"])
-def test_token_renewer_config(jp_server_config, jp_configurable_serverapp, renewer_type):
+@pytest.mark.parametrize(
+    "renewer_type,initial_auth_token", [("default", ""), ("custom", None), ("custom", "")]
+)
+def test_token_renewer_config(
+    jp_server_config, jp_configurable_serverapp, renewer_type, initial_auth_token
+):
     argv = ["--gateway-url=" + mock_gateway_url]
     if renewer_type == "custom":
         argv.append(
             "--GatewayClient.gateway_token_renewer_class=tests.test_gateway.CustomTestTokenRenewer"
         )
+    if initial_auth_token is None:
+        argv.append("--GatewayClient.auth_token=None")
 
     GatewayClient.clear_instance()
     app = jp_configurable_serverapp(argv=argv)
@@ -331,6 +337,11 @@ def test_token_renewer_config(jp_server_config, jp_configurable_serverapp, renew
             gw_client.auth_header_key, gw_client.auth_scheme, gw_client.auth_token or ""
         )
         assert token == CustomTestTokenRenewer.TEST_EXPECTED_TOKEN_VALUE
+    gw_client.load_connection_args()
+    if renewer_type == "default" or initial_auth_token is None:
+        assert gw_client.auth_token == initial_auth_token
+    else:
+        assert gw_client.auth_token == CustomTestTokenRenewer.TEST_EXPECTED_TOKEN_VALUE
 
 
 @pytest.mark.parametrize(