assembly: improve element auto naming

If a new element is created pointing to a named element, it will
inherit its name. If not, then check to see if the element is pointing
to an origin feature or datum, and inherit its name if so.

freecad/asm3/assembly.py

@@ -964,6 +964,7 @@ class AsmElement(AsmBase):
 
             elements = group.Proxy.getAssembly().getElementGroup()
             idx = -1
+            newElement = False
             if not element:
                 if not allowDuplicate:
                     # try to search the element group for an existing element
@@ -976,6 +977,7 @@ class AsmElement(AsmBase):
                         r = getattr(e,'Radius',None)
                         if (not radius and not r) or radius==r:
                             return e
+                newElement = True
                 element = AsmElement.create(name,elements)
                 if radius:
                     element.addProperty('App::PropertyFloat','Radius','','')
@@ -986,6 +988,31 @@ class AsmElement(AsmBase):
                 elements.cacheChildLabel()
 
             element.setLink(sobj,subname[dot+1:])
+            if newElement:
+                linked = element.LinkedObject
+                objPath = None
+                if isinstance(linked,tuple):
+                    objPath = logger.catchDebug('', linked[0].getSubObjectList, linked[1])
+                if objPath and len(objPath)>2 \
+                           and isTypeOf(objPath[2], AsmElement) \
+                           and objPath[2].Label != objPath[2].Name \
+                           and objPath[2].Label != '_' + objPath[2].Name:
+                    assembly = objPath[2].Proxy.getAssembly().Object
+                    label = objPath[2].Label
+                    idx = label.rfind('@')
+                    if idx > 0:
+                        label = label[:idx]
+                    element.Label = label + '@' + assembly.Label
+                else:
+                    target = element.getLinkedObject(True)
+                    if target and (target.isDerivedFrom('App::OriginFeature') \
+                                    or target.isDerivedFrom('Part::Datum')):
+                        label = target.Label
+                        parent = target.getParentGeoFeatureGroup()
+                        if parent:
+                            label += '@' + parent.Label
+                        element.Label = label
+
             element.recompute()
             if undo:
                 FreeCAD.closeActiveTransaction()