Also shorten unused IDs when --shorten-ids is specified

scour/scour.py

@@ -663,6 +663,9 @@ def shortenIDs(doc, prefix, unprotectedElements=None):
    idList.sort(reverse=True)
    idList = [rid for count, rid in idList]
    
+   # Add unreferenced IDs to end of idList in arbitrary order
+   idList.extend([rid for rid in unprotectedElements if not rid in idList])
+
    curIdNum = 1
 
    for rid in idList:
@@ -712,8 +715,11 @@ def renameID(doc, idFrom, idTo, identifiedElements, referencedIDs):
    definingNode.setAttribute("id", idTo)
    del identifiedElements[idFrom]
    identifiedElements[idTo] = definingNode
+   num += len(idFrom) - len(idTo)
 
-   referringNodes = referencedIDs[idFrom]
+   # Update references to renamed node
+   referringNodes = referencedIDs.get(idFrom)
+   if referringNodes is not None:
 
       # Look for the idFrom ID name in each of the referencing elements,
       # exactly like findReferencedElements would.