misc: override |default_if_none for lazy variables (#77947)

tests/test_formdata.py

@@ -2033,6 +2033,9 @@ def test_lazy_variables_missing(pub, variable_test_data):
         with pytest.raises(KeyError):
             assert context['form_var_foo_foo_xxx'] == 'bar'
 
+        tmpl = Template('{{form_var_foo_foo_baz_baz|default_if_none:"XXX"}}')
+        assert tmpl.render(context) == 'XXX'
+
 
 def test_lazy_variables_length(pub, variable_test_data):
     formdef = FormDef.select()[0]

wcs/qommon/templatetags/qommon.py

@@ -1104,3 +1104,11 @@ def translate(string, context=None):
     if string is None:
         return None
     return get_publisher().translate(string, context=context, register=True)
+
+
+@register.filter(is_safe=False)
+def default_if_none(value, arg):
+    value = unlazy(value)
+    if value is None:
+        return arg
+    return value