fix: Prevent crash in case of empty dataclasses (#56)

fix: Prevent crash in case of empty dataclasses

We iterate on `__dataclass_fields__` instead of `__annotations__`
since we already assert its existence.

References: #56

Author: jaredkhan

Diff for: src/pytkdocs/loader.py

@@ -405,14 +405,15 @@ def get_class_documentation(self, node: ObjectNode, select_members=None) -> Clas
             self.select_inherited_members and "__fields__" in all_members
         ):
             root_object.properties = ["dataclass"]
-            for field_name, annotation in all_members["__annotations__"].items():
-                if self.select(field_name, select_members) and (  # type: ignore
+
+            for field in all_members["__dataclass_fields__"].values():
+                if self.select(field.name, select_members) and (  # type: ignore
                     self.select_inherited_members
                     # Same comment as for Pydantic models
-                    or field_name
+                    or field.name
                     not in chain(*(getattr(cls, "__dataclass_fields__", {}).keys() for cls in class_.__mro__[1:-1]))
                 ):
-                    child_node = ObjectNode(obj=annotation, name=field_name, parent=node)
+                    child_node = ObjectNode(obj=field.type, name=field.name, parent=node)
                     root_object.add_child(self.get_annotated_dataclass_field(child_node))
 
         return root_object

Diff for: tests/fixtures/dataclass.py

@@ -8,3 +8,10 @@ class Person:
     name: str
     age: int
     """Field description."""
+
+
+@dataclass
+class Empty:
+    """A dataclass without any fields"""
+
+    pass

Diff for: tests/test_loader.py

@@ -148,6 +148,15 @@ def test_loading_dataclass():
     assert "dataclass" not in not_dataclass.properties
 
 
+def test_loading_empty_dataclass():
+    """Handle empty dataclasses."""
+    loader = Loader()
+    obj = loader.get_object_documentation("tests.fixtures.dataclass.Empty")
+    assert obj.docstring == "A dataclass without any fields"
+    assert len(obj.attributes) == 0
+    assert "dataclass" in obj.properties
+
+
 def test_loading_pydantic_model():
     """Handle Pydantic models."""
     loader = Loader()