[Identity] Fix TypeError in certain Entra responses

Signed-off-by: Paul Van Eck <paulvaneck@microsoft.com>

Author: pvaneck

sdk/identity/azure-identity/CHANGELOG.md

@@ -12,6 +12,8 @@
 
 ### Bugs Fixed
 
+- Fixed an issue where an unhelpful TypeError was raised during Entra ID token requests that returned certain non-JSON responses. Now, a ClientAuthenticationError is raised with the full response for better troubleshooting. ([#44258](https://github.com/Azure/azure-sdk-for-python/pull/44258))
+
 ### Other Changes
 
 ## 1.26.0b1 (2025-11-07)

sdk/identity/azure-identity/azure/identity/_internal/aad_client_base.py

@@ -139,6 +139,11 @@ def _process_response(self, response: PipelineResponse, request_time: int, **kwa
             ContentDecodePolicy.CONTEXT_NAME
         ) or ContentDecodePolicy.deserialize_from_http_generics(response.http_response)
 
+        if not content:
+            raise ClientAuthenticationError(
+                message="No response content from Microsoft Entra ID", response=response.http_response
+            )
+
         cache = self._get_cache(**kwargs)
         if response.http_request.body.get("grant_type") == "refresh_token":
             if content.get("error") == "invalid_grant":

sdk/identity/azure-identity/tests/test_aad_client.py

@@ -51,6 +51,29 @@ def test_error_reporting():
         transport.send.reset_mock()
 
 
+def test_none_content_handling():
+    """Test that _process_response handles None content without raising TypeError"""
+    http_response = mock_response(status_code=200)
+    http_response.text = Mock(return_value="")
+
+    # Create a mock PipelineResponse with empty context
+    mock_pipeline_response = Mock()
+    mock_pipeline_response.context = {}
+    mock_pipeline_response.http_response = http_response
+    mock_pipeline_response.http_request = Mock()
+    mock_pipeline_response.http_request.body = {}
+
+    with patch("azure.identity._internal.aad_client_base.ContentDecodePolicy") as mock_policy:
+        mock_policy.CONTEXT_NAME = "content_decode_policy"
+        mock_policy.deserialize_from_http_generics = Mock(return_value=None)
+
+        transport = Mock()
+        client = AadClient("tenant id", "client id", transport=transport)
+
+        with pytest.raises(ClientAuthenticationError):
+            client._process_response(mock_pipeline_response, int(1234567890))
+
+
 @pytest.mark.skip(reason="Adding body to HttpResponseError str. Not an issue bc we don't automatically log errors")
 def test_exceptions_do_not_expose_secrets():
     secret = "secret"