First Pass

src/specklepy/objects/graph_traversal/default_traversal.py

@@ -0,0 +1,28 @@
+from specklepy.objects.base import Base
+from specklepy.objects.graph_traversal.traversal import GraphTraversal, TraversalRule
+
+DISPLAY_VALUE_PROPERTY_ALIASES = {"displayValue", "@displayValue"}
+ELEMENTS_PROPERTY_ALIASES = {"elements", "@elements"}
+
+
+def has_display_value(x: Base):
+    return any(hasattr(x, alias) for alias in DISPLAY_VALUE_PROPERTY_ALIASES)
+
+
+def create_default_traversal_function() -> GraphTraversal:
+    """
+    Traversal func for traversing the root object of a Speckle Model
+    """
+
+    convertible_rule = TraversalRule(
+        [lambda b: b.speckle_type != "Base", has_display_value],
+        lambda _: ELEMENTS_PROPERTY_ALIASES,
+    )
+
+    default_rule = TraversalRule(
+        [lambda _: True],
+        lambda o: o.get_member_names(),  # NOTE: Unlike the C# implementation, this does not ignore Obsolete members
+        False,
+    )
+
+    return GraphTraversal([convertible_rule, default_rule])

src/specklepy/objects/graph_traversal/traversal.py

@@ -7,6 +7,11 @@
 
 
 class ITraversalRule(Protocol):
+
+    @property
+    def should_return(self) -> bool:
+        pass
+
     def get_members_to_traverse(self, o: Base) -> Set[str]:
         """Get the members to traverse."""
         pass
@@ -50,10 +55,13 @@ def traverse(self, root: Base) -> Iterator[TraversalContext]:
 
         while len(stack) > 0:
             head = stack.pop()
-            yield head
 
             current = head.current
             active_rule = self._get_active_rule_or_default_rule(current)
+
+            if active_rule.should_return:
+                yield head
+
             members_to_traverse = active_rule.get_members_to_traverse(current)
             for child_prop in members_to_traverse:
                 try:
@@ -114,6 +122,11 @@ def _get_active_rule(self, o: Base) -> Optional[ITraversalRule]:
 class TraversalRule:
     _conditions: Collection[Callable[[Base], bool]]
     _members_to_traverse: Callable[[Base], Iterable[str]]
+    _should_return_to_output: bool = True
+
+    @property
+    def should_return(self) -> bool:
+        return self._should_return_to_output
 
     def get_members_to_traverse(self, o: Base) -> Set[str]:
         return set(self._members_to_traverse(o))