fix: correct "empty option" behavior for ObjectRef schema type

src/wuttaweb/forms/schema.py

@@ -207,6 +207,11 @@ class ObjectRef(colander.SchemaType):
 
     def serialize(self, node, appstruct):
         """ """
+        # nb. normalize to empty option if no object ref, so that
+        # works as expected
+        if self.empty_option and not appstruct:
+            return self.empty_option[0]
+
         if appstruct is colander.null:
             return colander.null
 

src/wuttaweb/forms/widgets.py

@@ -102,7 +102,7 @@ class ObjectRefWidget(SelectWidget):
         # add url, only if rendering readonly
         readonly = kw.get('readonly', self.readonly)
         if readonly:
-            if 'url' not in values and self.url and field.schema.model_instance:
+            if 'url' not in values and self.url and hasattr(field.schema, 'model_instance'):
                 values['url'] = self.url(field.schema.model_instance)
 
         return values

src/wuttaweb/templates/deform/readonly/objectref.pt

@@ -4,6 +4,6 @@
     ${str(field.schema.model_instance or '')}
   </a>
   <span tal:condition="not url">
-    ${str(field.schema.model_instance or '')}
+    ${str(getattr(field.schema, 'model_instance', None) or '')}
   </span>
 </tal:omit>

tests/forms/test_schema.py

@@ -102,6 +102,11 @@ class TestObjectRef(DataTestCase):
         value = typ.serialize(node, person)
         self.assertEqual(value, person.uuid.hex)
 
+        # null w/ empty option
+        typ = mod.ObjectRef(self.request, empty_option=('bad', 'BAD'))
+        value = typ.serialize(node, colander.null)
+        self.assertEqual(value, 'bad')
+
     def test_deserialize(self):
         model = self.app.model
         node = colander.SchemaNode(colander.String())

tests/forms/test_widgets.py

@@ -61,6 +61,7 @@ class TestObjectRefWidget(WebTestCase):
         self.session.add(person)
         self.session.commit()
 
+        # standard
         node = colander.SchemaNode(PersonRef(self.request, session=self.session))
         widget = self.make_widget()
         field = self.make_field(node)
@@ -68,6 +69,15 @@ class TestObjectRefWidget(WebTestCase):
         self.assertIn('cstruct', values)
         self.assertNotIn('url', values)
 
+        # readonly w/ empty option
+        node = colander.SchemaNode(PersonRef(self.request, session=self.session,
+                                             empty_option=('_empty_', '(empty)')))
+        widget = self.make_widget(readonly=True, url=lambda obj: '/foo')
+        field = self.make_field(node)
+        values = widget.get_template_values(field, '_empty_', {})
+        self.assertIn('cstruct', values)
+        self.assertNotIn('url', values)
+
 
 class TestFileDownloadWidget(WebTestCase):