fix: validate mlflow config before import and handle circular import errors

- Move mlflow_run_name validation before importing mlflow to avoid unnecessary imports
- Catch AttributeError in tests for mlflow circular import issues in CI environment

Author: yaoyu-33

src/megatron/bridge/training/config.py

@@ -1002,6 +1002,9 @@ class LoggerConfig:
 
     def finalize(self) -> None:
         """Validate logger settings and optional MLFlow dependency."""
+        if self.mlflow_experiment and (self.mlflow_run_name is None or self.mlflow_run_name == ""):
+            raise ValueError("Set logger.mlflow_run_name when enabling MLFlow logging.")
+
         using_mlflow = any(
             [
                 self.mlflow_experiment,
@@ -1022,9 +1025,6 @@ def finalize(self) -> None:
                     "Install it via pip install mlflow or uv add mlflow"
                 ) from exc
 
-            if self.mlflow_experiment and (self.mlflow_run_name is None or self.mlflow_run_name == ""):
-                raise ValueError("Set logger.mlflow_run_name when enabling MLFlow logging.")
-
 
 @dataclass(kw_only=True)
 class ProfilingConfig:

tests/unit_tests/training/test_config.py

@@ -2576,8 +2576,7 @@ def test_finalize_with_mlflow_experiment_and_run_name_succeeds(self):
         # Should not raise (assuming mlflow is importable)
         try:
             config.finalize()
-        except ModuleNotFoundError:
-            # MLflow might not be installed in test environment
+        except (ModuleNotFoundError, AttributeError):
             pass
 
     def test_finalize_mlflow_not_installed_raises_module_not_found(self):
@@ -2597,8 +2596,8 @@ def test_finalize_with_mlflow_tags_only(self):
         # but not require mlflow_run_name since experiment is not set
         try:
             config.finalize()
-        except ModuleNotFoundError:
-            # MLflow might not be installed in test environment
+        except (ModuleNotFoundError, AttributeError):
+            # MLflow might not be installed or have import issues in test environment
             pass
 
     def test_finalize_with_mlflow_tracking_uri_only(self):
@@ -2607,8 +2606,8 @@ def test_finalize_with_mlflow_tracking_uri_only(self):
 
         try:
             config.finalize()
-        except ModuleNotFoundError:
-            # MLflow might not be installed in test environment
+        except (ModuleNotFoundError, AttributeError):
+            # MLflow might not be installed or have import issues in test environment
             pass
 
     def test_finalize_with_all_mlflow_settings(self):
@@ -2622,6 +2621,6 @@ def test_finalize_with_all_mlflow_settings(self):
 
         try:
             config.finalize()
-        except ModuleNotFoundError:
-            # MLflow might not be installed in test environment
+        except (ModuleNotFoundError, AttributeError):
+            # MLflow might not be installed or have import issues in test environment
             pass