Index: openacs-4/packages/acs-tcl/tcl/object-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/object-procs.tcl,v
diff -u -r1.14.2.5 -r1.14.2.6
--- openacs-4/packages/acs-tcl/tcl/object-procs.tcl	6 Mar 2021 16:58:14 -0000	1.14.2.5
+++ openacs-4/packages/acs-tcl/tcl/object-procs.tcl	14 Jul 2022 16:55:16 -0000	1.14.2.6
@@ -179,6 +179,38 @@
     return [db_string object_exists {} -default 0]
 }
 
+ad_proc -private acs_object::is_type_p {
+    -object_id:required
+    -object_types:required
+    -no_hierarchy:boolean
+} {
+    Returns whether an object is of a given object type.
+} {
+    set object_types [ns_dbquotelist $object_types]
+    set no_hierarchy_p [expr {$no_hierarchy_p ? "t" : "f"}]
+    return [db_0or1row check_types [subst -nocommands {
+        with recursive hierarchy as
+        (
+         select o.object_type, t.supertype
+         from acs_objects o, acs_object_types t
+         where o.object_id = :object_id
+           and o.object_type = t.object_type
+
+         union
+
+         select t.object_type, t.supertype
+         from acs_object_types t,
+              hierarchy h
+         where :no_hierarchy_p = 'f'
+           and t.object_type = h.supertype
+           and h.object_type not in ($object_types)
+         )
+        select 1 from hierarchy
+        where object_type in ($object_types)
+        fetch first 1 rows only
+    }]]
+}
+
 ad_proc -public acs_object::set_context_id {
     {-object_id:required}
     {-context_id:required}
Index: openacs-4/packages/acs-tcl/tcl/tcl-documentation-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/tcl-documentation-procs.tcl,v
diff -u -r1.61.2.25 -r1.61.2.26
--- openacs-4/packages/acs-tcl/tcl/tcl-documentation-procs.tcl	14 Jul 2022 15:17:09 -0000	1.61.2.25
+++ openacs-4/packages/acs-tcl/tcl/tcl-documentation-procs.tcl	14 Jul 2022 16:55:16 -0000	1.61.2.26
@@ -1831,7 +1831,31 @@
     return 0
 }
 
+ad_page_contract_filter object_type { name object_id types } {
 
+    Checks whether the supplied object_id is an acs_object of one of
+    the types specified in the flag parameters.
+
+    The check will take the object_type hierarchy into account
+    e.g. will always succeed if one of the types is "acs_object". In
+    this case the filter will just behave as an existance check.
+
+} {
+    # First make sure the object_id formally correct
+    if { ![ad_page_contract_filter_proc_object_id $name object_id] } {
+        return 0
+    }
+
+    if { ![acs_object::is_type_p \
+               -object_id $object_id \
+               -object_types $types] } {
+        ad_complain [_ acs-tcl.lt_invalid_object_type]
+        return 0
+    }
+
+    return 1
+}
+
 ad_page_contract_filter range { name value range } {
     Checks whether the value falls between the specified range.
     Range must be a list of two elements: min and max.