snapshots: do not fail on workflow form fields (#50832)

tests/test_snapshots.py

@@ -13,6 +13,7 @@ from wcs.data_sources import NamedDataSource
 from wcs.formdef import FormDef
 from wcs.qommon.form import UploadedFile
 from wcs.qommon.misc import localstrftime
+from wcs.wf.form import FormWorkflowStatusItem, WorkflowFormFieldsFormDef
 from wcs.workflows import Workflow
 from wcs.workflows import ExportToModel
 from wcs.wscalls import NamedWsCall
@@ -439,6 +440,30 @@ def test_workflow_with_model_snapshot_browse(pub):
         assert len(os.listdir(os.path.join(pub.app_dir, 'models'))) == 3 + i
 
 
+def test_workflow_with_form_snapshot_browse(pub):
+    create_superuser(pub)
+    create_role()
+
+    Workflow.wipe()
+    wf = Workflow(name='status')
+    st1 = wf.add_status('Status1', 'st1')
+
+    display_form = FormWorkflowStatusItem()
+    display_form.id = '_x'
+    display_form.varname = 'xxx'
+    display_form.formdef = WorkflowFormFieldsFormDef(item=display_form)
+    st1.items.append(display_form)
+    display_form.parent = st1
+    wf.store()
+    snapshot = pub.snapshot_class.select_object_history(wf)[0]
+
+    app = login(get_app(pub))
+    resp = app.get(
+        '/backoffice/workflows/%s/history/%s/view/status/st1/items/_x/fields/' % (wf.id, snapshot.id)
+    )
+    assert 'The fields are readonly' in resp.text  # ok, no error
+
+
 def test_wscall_snapshot_browse(pub):
     create_superuser(pub)
     create_role()

wcs/admin/fields.py

@@ -354,9 +354,10 @@ class FieldsDirectory(Directory):
             get_response().filter['sidebar'] = htmltext('<div class="infonotice"><p>%s</p></div>') % _(
                 self.readonly_message
             )
-            get_response().filter['sidebar'] += utils.snapshot_info_block(
-                snapshot=self.objectdef.snapshot_object
-            )
+            if hasattr(self.objectdef, 'snapshot_object'):
+                get_response().filter['sidebar'] += utils.snapshot_info_block(
+                    snapshot=self.objectdef.snapshot_object
+                )
         else:
             get_response().filter['sidebar'] = str(self.get_new_field_form(self.page_id))
         r += self.index_bottom()