fix: better normalisation of group names

Author: yt-ms

src/structurizr/model/groupable_element.py

@@ -28,23 +28,26 @@ class GroupableElementIO(ElementIO, ABC):
     Define a superclass for all elements that can be included in a group.
 
     Attributes:
-        group (str): The name of thegroup in which this element should be included.
+        group (str): The name of thegroup in which this element should be included, or
+            None if no group.
     """
 
-    group: Optional[str] = ""
+    group: Optional[str]
 
 
 class GroupableElement(Element, ABC):
     """
     Define a superclass for all elements that can be included in a group.
 
     Attributes:
-        group (str): The name of thegroup in which this element should be included.
+        group (str): The name of thegroup in which this element should be included, or
+            None if no group.
     """
 
-    def __init__(self, *, group: str = "", **kwargs):
+    def __init__(self, *, group: Optional[str] = None, **kwargs):
         """Initialise a GroupableElement."""
         super().__init__(**kwargs)
+        group = group.strip() or None if group else None
         self.group = group
 
     @classmethod

tests/unit/model/test_groupable_element.py

@@ -23,6 +23,15 @@ class ConcreteElement(ChildlessMixin, GroupableElement):
     pass
 
 
+def test_group_name_normalisation():
+    """Test that empty group names are normalised to None."""
+    assert ConcreteElement(name="Name").group is None
+    assert ConcreteElement(name="Name", group=None).group is None
+    assert ConcreteElement(name="Name", group="").group is None
+    assert ConcreteElement(name="Name", group=" ").group is None
+    assert ConcreteElement(name="Name", group=" g1 ").group == "g1"
+
+
 def test_group_in_json():
     """Test the group field is output to JSON."""
     element = ConcreteElement(name="Name", group="Group 1")