fix(assembly): extend findPlacement() datum and origin handling (#55)

Add support for missing datum and origin object types in the Assembly
solver's findPlacement() function:

- App::Plane: handle XY/XZ/YZ origin planes with correct rotations
- App::Point: handle origin point (identity placement)
- PartDesign::Line: extract edge midpoint and direction from shape
- PartDesign::Point: extract vertex position from shape geometry
  instead of returning raw obj.Placement
- Add obj.Shape.isNull() validation to all PartDesign datum branches
- PartDesign::Plane falls back to obj.Placement on invalid shape
  instead of falling through to App.Placement()

Closes #55

src/Mod/Assembly/UtilsAssembly.py

@@ -49,7 +49,9 @@ def activePartOrAssembly():
 
 def activeAssembly():
     active_assembly = activePartOrAssembly()
-    if active_assembly is not None and active_assembly.isDerivedFrom("Assembly::AssemblyObject"):
+    if active_assembly is not None and active_assembly.isDerivedFrom(
+        "Assembly::AssemblyObject"
+    ):
         if active_assembly.ViewObject.isInEditMode():
             return active_assembly
 
@@ -59,7 +61,9 @@ def activeAssembly():
 def activePart():
     active_part = activePartOrAssembly()
 
-    if active_part is not None and not active_part.isDerivedFrom("Assembly::AssemblyObject"):
+    if active_part is not None and not active_part.isDerivedFrom(
+        "Assembly::AssemblyObject"
+    ):
         return active_part
 
     return None
@@ -120,7 +124,9 @@ def number_of_components_in(assembly):
 def isLink(obj):
     # If element count is not 0, then its a link group in which case the Link
     # is a container and it's the LinkElement that is linking to external doc.
-    return (obj.TypeId == "App::Link" and obj.ElementCount == 0) or obj.TypeId == "App::LinkElement"
+    return (
+        obj.TypeId == "App::Link" and obj.ElementCount == 0
+    ) or obj.TypeId == "App::LinkElement"
 
 
 def isLinkGroup(obj):
@@ -375,7 +381,9 @@ def getGlobalPlacement(ref, targetObj=None):
     if not isRefValid(ref, 1):
         return App.Placement()
 
-    if targetObj is None:  # If no targetObj is given, we consider it's the getObject(ref)
+    if (
+        targetObj is None
+    ):  # If no targetObj is given, we consider it's the getObject(ref)
         targetObj = getObject(ref)
         if targetObj is None:
             return App.Placement()
@@ -520,11 +528,17 @@ def findElementClosestVertex(ref, mousePos):
 
         for i, edge in enumerate(edges):
             curve = edge.Curve
-            if curve.TypeId == "Part::GeomCircle" or curve.TypeId == "Part::GeomEllipse":
+            if (
+                curve.TypeId == "Part::GeomCircle"
+                or curve.TypeId == "Part::GeomEllipse"
+            ):
                 center_points.append(curve.Location)
                 center_points_edge_indexes.append(i)
 
-            elif _type == "Part::GeomCylinder" and curve.TypeId == "Part::GeomBSplineCurve":
+            elif (
+                _type == "Part::GeomCylinder"
+                and curve.TypeId == "Part::GeomBSplineCurve"
+            ):
                 # handle special case of 2 cylinder intersecting.
                 for j, facej in enumerate(obj.Shape.Faces):
                     surfacej = facej.Surface
@@ -553,7 +567,9 @@ def findElementClosestVertex(ref, mousePos):
         if _type == "Part::GeomCylinder" or _type == "Part::GeomCone":
             centerOfG = face.CenterOfGravity - surface.Center
             centerPoint = surface.Center + centerOfG
-            centerPoint = centerPoint + App.Vector().projectToLine(centerOfG, surface.Axis)
+            centerPoint = centerPoint + App.Vector().projectToLine(
+                centerOfG, surface.Axis
+            )
             face_points.append(centerPoint)
         else:
             face_points.append(face.CenterOfGravity)
@@ -623,7 +639,8 @@ def color_from_unsigned(c):
 
 def getJointsOfType(asm, jointTypes):
     if not (
-        asm.isDerivedFrom("Assembly::AssemblyObject") or asm.isDerivedFrom("Assembly::AssemblyLink")
+        asm.isDerivedFrom("Assembly::AssemblyObject")
+        or asm.isDerivedFrom("Assembly::AssemblyLink")
     ):
         return []
 
@@ -763,7 +780,9 @@ def getSubMovingParts(obj, partsAsSolid):
 
     if isLink(obj):
         linked_obj = obj.getLinkedObject()
-        if linked_obj.isDerivedFrom("App::Part") or linked_obj.isDerivedFrom("Part::Feature"):
+        if linked_obj.isDerivedFrom("App::Part") or linked_obj.isDerivedFrom(
+            "Part::Feature"
+        ):
             return [obj]
 
     return []
@@ -996,7 +1015,7 @@ def findPlacement(ref, ignoreVertex=False):
     vtx = getElementName(ref[1][1])
 
     if not elt or not vtx:
-        # case of whole parts such as PartDesign::Body or App/PartDesign::CordinateSystem/Point/Line/Plane.
+        # Origin objects (App::Line, App::Plane, App::Point)
         if obj.TypeId == "App::Line":
             if obj.Role == "X_Axis":
                 return App.Placement(App.Vector(), App.Rotation(0.5, 0.5, 0.5, 0.5))
@@ -1005,9 +1024,25 @@ def findPlacement(ref, ignoreVertex=False):
             if obj.Role == "Z_Axis":
                 return App.Placement(App.Vector(), App.Rotation(-0.5, 0.5, -0.5, 0.5))
 
-        # PartDesign datum planes (including ZTools datums like ZPlane_Mid, ZPlane_Offset)
+        if obj.TypeId == "App::Plane":
+            if obj.Role == "XY_Plane":
+                return App.Placement()
+            if obj.Role == "XZ_Plane":
+                return App.Placement(
+                    App.Vector(), App.Rotation(App.Vector(1, 0, 0), -90)
+                )
+            if obj.Role == "YZ_Plane":
+                return App.Placement(
+                    App.Vector(), App.Rotation(App.Vector(0, 1, 0), 90)
+                )
+            return App.Placement()
+
+        if obj.TypeId == "App::Point":
+            return App.Placement()
+
+        # PartDesign datum planes
         if obj.isDerivedFrom("PartDesign::Plane"):
-            if hasattr(obj, "Shape") and obj.Shape.Faces:
+            if hasattr(obj, "Shape") and not obj.Shape.isNull() and obj.Shape.Faces:
                 face = obj.Shape.Faces[0]
                 surface = face.Surface
                 plc = App.Placement()
@@ -1015,9 +1050,28 @@ def findPlacement(ref, ignoreVertex=False):
                 if hasattr(surface, "Rotation") and surface.Rotation is not None:
                     plc.Rotation = App.Rotation(surface.Rotation)
                 return obj.Placement.inverse() * plc
+            return obj.Placement
+
+        # PartDesign datum lines
+        if obj.isDerivedFrom("PartDesign::Line"):
+            if hasattr(obj, "Shape") and not obj.Shape.isNull() and obj.Shape.Edges:
+                edge = obj.Shape.Edges[0]
+                points = getPointsFromVertexes(edge.Vertexes)
+                mid = (points[0] + points[1]) * 0.5
+                direction = round_vector(edge.Curve.Direction)
+                plane = Part.Plane(App.Vector(), direction)
+                plc = App.Placement()
+                plc.Base = mid
+                plc.Rotation = App.Rotation(plane.Rotation)
+                return obj.Placement.inverse() * plc
+            return obj.Placement
 
         # PartDesign datum points
         if obj.isDerivedFrom("PartDesign::Point"):
+            if hasattr(obj, "Shape") and not obj.Shape.isNull() and obj.Shape.Vertexes:
+                plc = App.Placement()
+                plc.Base = obj.Shape.Vertexes[0].Point
+                return obj.Placement.inverse() * plc
             return obj.Placement
 
         return App.Placement()
@@ -1080,9 +1134,14 @@ def findPlacement(ref, ignoreVertex=False):
             if surface.TypeId == "Part::GeomCylinder":
                 centerOfG = face.CenterOfGravity - surface.Center
                 centerPoint = surface.Center + centerOfG
-                centerPoint = centerPoint + App.Vector().projectToLine(centerOfG, surface.Axis)
+                centerPoint = centerPoint + App.Vector().projectToLine(
+                    centerOfG, surface.Axis
+                )
                 plc.Base = centerPoint
-            elif surface.TypeId == "Part::GeomTorus" or surface.TypeId == "Part::GeomSphere":
+            elif (
+                surface.TypeId == "Part::GeomTorus"
+                or surface.TypeId == "Part::GeomSphere"
+            ):
                 plc.Base = surface.Center
             elif surface.TypeId == "Part::GeomCone":
                 plc.Base = surface.Apex
@@ -1100,7 +1159,8 @@ def findPlacement(ref, ignoreVertex=False):
                 plc.Base = (center_point.x, center_point.y, center_point.z)
 
             elif (
-                surface.TypeId == "Part::GeomCylinder" and curve.TypeId == "Part::GeomBSplineCurve"
+                surface.TypeId == "Part::GeomCylinder"
+                and curve.TypeId == "Part::GeomBSplineCurve"
             ):
                 # handle special case of 2 cylinder intersecting.
                 plc.Base = findCylindersIntersection(obj, surface, edge, elt_index)
@@ -1394,13 +1454,16 @@ def generatePropertySettings(documentObject):
             commands.append(f"obj.{propertyName} = {propertyValue:.5f}")
         elif propertyType == "App::PropertyInt" or propertyType == "App::PropertyBool":
             commands.append(f"obj.{propertyName} = {propertyValue}")
-        elif propertyType == "App::PropertyString" or propertyType == "App::PropertyEnumeration":
+        elif (
+            propertyType == "App::PropertyString"
+            or propertyType == "App::PropertyEnumeration"
+        ):
             commands.append(f'obj.{propertyName} = "{propertyValue}"')
         elif propertyType == "App::PropertyPlacement":
             commands.append(
                 f"obj.{propertyName} = App.Placement("
                 f"App.Vector({propertyValue.Base.x:.5f},{propertyValue.Base.y:.5f},{propertyValue.Base.z:.5f}),"
-                f"App.Rotation(*{[round(n,5) for n in propertyValue.Rotation.getYawPitchRoll()]}))"
+                f"App.Rotation(*{[round(n, 5) for n in propertyValue.Rotation.getYawPitchRoll()]}))"
             )
         elif propertyType == "App::PropertyXLinkSubHidden":
             commands.append(