tdf#130857 ui-rules-enforcer: Check column doesn't have multiple same renderers

Add a check to the UI rules enforcer that checks that
no column (GtkTreeViewColumn) contains multiple
renderers of the same type, e.g. no 2 GtkCellRendererToggle.

This wouldn't work at least with the qt weld implementation
as that one maps the different types of renderers to a
role, but setting/displaying multiple different values for the
same role in the same column isn't possible.

All previously detected occurences (that had dummy
columns for other reasons) were addressed in previous
commits, so there is currently no such issue left.
Adding the check can help to identify/avoid new
issues in the future.

Change-Id: I637e50477ce41a7ceca8f9cf5830e383b5393c69
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/207309
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

bin/ui-rules-enforcer.py

@@ -664,6 +664,11 @@ def enforce_treeview_column_rules(current):
   if len(columns[0]) >= 2 and columns[0][0] == "GtkCellRendererPixbuf" and columns[0][1] == "GtkCellRendererToggle":
     raise Exception(sys.argv[1] + ": treeview has special toggle and pixbuf columns/renderers in wrong order: ", current.attrib.get("id"))
 
+  # ensure that column don't contain multiple cell renderers of the same type
+  for col in columns:
+    if len(col) != len(set(col)):
+      raise Exception(sys.argv[1] + ": Multiple cell renderers of the same type not supported in one column: ", current.attrib.get("id"))
+
 with open(sys.argv[1], encoding="utf-8") as f:
   header = f.readline()
   f.seek(0)