refactor: implement PR suggestions

Author: betinacosta

src/sap_cloud_sdk/core/protocol/http/models.py

@@ -12,6 +12,7 @@
 
 import requests
 from oauthlib.oauth2 import BackendApplicationClient
+from oauthlib.oauth2.rfc6749.errors import FatalClientError
 from requests_oauthlib import OAuth2Session
 
 from sap_cloud_sdk.core._tenant import (
@@ -136,6 +137,8 @@ def _fetch_token(self, tenant_subdomain: Optional[str]) -> OAuth2Session:
                 )
                 last_exc = None
                 break
+            except FatalClientError:
+                raise
             except Exception as exc:
                 last_exc = exc
                 if attempt < _TOKEN_FETCH_MAX_ATTEMPTS - 1:

tests/core/unit/test_http_client.py

@@ -2,6 +2,8 @@
 
 from unittest.mock import MagicMock, call, patch
 
+from oauthlib.oauth2.rfc6749.errors import InvalidClientError
+
 import pytest
 import requests
 
@@ -382,3 +384,16 @@ def test_no_sleep_after_final_attempt(self):
             with pytest.raises(RuntimeError):
                 provider._fetch_token(None)
         assert mock_sleep.call_count == 2  # only after attempts 1 and 2, not 3
+
+    def test_fatal_client_error_raises_immediately_without_retry(self):
+        provider = self._make_provider()
+        fatal = InvalidClientError()
+        with patch("sap_cloud_sdk.core.protocol.http.models.OAuth2Session") as mock_cls, \
+             patch("sap_cloud_sdk.core.protocol.http.models.time.sleep") as mock_sleep:
+            mock_session = MagicMock()
+            mock_cls.return_value = mock_session
+            mock_session.fetch_token.side_effect = fatal
+            with pytest.raises(InvalidClientError):
+                provider._fetch_token(None)
+        assert mock_session.fetch_token.call_count == 1
+        mock_sleep.assert_not_called()