Fixed the FOBS lazy loading issue (#3121)

* Fixed the FOBS lazy loading issue

* Fixed format

* Added check for builtins without module name

nvflare/fuel/utils/fobs/fobs.py

@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import builtins
 import importlib
 import inspect
 import logging
@@ -66,15 +67,12 @@ def _get_type_name(cls: Type) -> str:
 
 def _load_class(type_name: str):
     try:
-        parts = type_name.split(".")
-        if len(parts) == 1:
-            parts = ["builtins", type_name]
-
-        mod = __import__(parts[0])
-        for comp in parts[1:]:
-            mod = getattr(mod, comp)
-
-        return mod
+        if "." in type_name:
+            module_name, class_name = type_name.rsplit(".", 1)
+            module = importlib.import_module(module_name)
+            return getattr(module, class_name)
+        else:
+            return getattr(builtins, type_name)
     except Exception as ex:
         raise TypeError(f"Can't load class {type_name}: {ex}")
 

tests/unit_test/fuel/utils/fobs/fobs_test.py

@@ -28,14 +28,15 @@ class TestFobs:
     NUMBER = 123456
     FLOAT = 123.456
     NAME = "FOBS Test"
+    SET = {4, 5, 6}
     NOW = datetime.now()
 
     test_data = {
         "str": "Test string",
         "number": NUMBER,
         "float": FLOAT,
         "list": [7, 8, 9],
-        "set": {4, 5, 6},
+        "set": SET,
         "tuple": ("abc", "xyz"),
         "time": NOW,
     }
@@ -44,11 +45,7 @@ def test_builtin(self):
         buf = fobs.dumps(TestFobs.test_data)
         data = fobs.loads(buf)
         assert data["number"] == TestFobs.NUMBER
-
-    def test_aliases(self):
-        buf = fobs.dumps(TestFobs.test_data)
-        data = fobs.loads(buf)
-        assert data["number"] == TestFobs.NUMBER
+        assert data["set"] == TestFobs.SET
 
     def test_unsupported_classes(self):
         with pytest.raises(TypeError):