fields: item fields are stored as None if value is empty string (#59542)

tests/workflow/test_formdata.py

@@ -2,7 +2,8 @@ import pytest
 from quixote import cleanup, get_response
 
 from wcs import sessions
-from wcs.fields import EmailField, StringField
+from wcs.carddef import CardDef
+from wcs.fields import EmailField, ItemField, StringField
 from wcs.formdef import FormDef
 from wcs.qommon.http_request import HTTPRequest
 from wcs.wf.create_formdata import CreateFormdataWorkflowStatusItem, Mapping
@@ -278,3 +279,59 @@ def test_create_formdata_attach_to_history(two_pubs):
     target_formdef.remove_self()
     formdata.refresh_from_storage()
     assert 'deleted' in str(formdata.evolution[-1].parts[0].view())
+
+
+def test_create_formdata_item_optional_mapping(pub):
+    FormDef.wipe()
+    CardDef.wipe()
+
+    carddef = CardDef()
+    carddef.name = 'Bar'
+    carddef.fields = [
+        StringField(id='0', label='Bar', varname='bar'),
+    ]
+    carddef.digest_templates = {'default': '{{ form_var_bar }}'}
+    carddef.store()
+    carddef.data_class().wipe()
+
+    for i in range(0, 4):
+        carddata = carddef.data_class()()
+        carddata.data = {'0': 'Bar %s' % (i + 1)}
+        carddata.store()
+
+    target_formdef = FormDef()
+    target_formdef.name = 'Foo'
+    target_formdef.fields = [
+        ItemField(id='0', label='Bar', type='item', data_source={'type': 'carddef:bar'}, required=False),
+    ]
+    target_formdef.store()
+    target_formdef.data_class().wipe()
+
+    wf = Workflow(name='create-formdata')
+    wf.possible_status = Workflow.get_default_workflow().possible_status[:]
+    create = CreateFormdataWorkflowStatusItem()
+    create.label = 'create a new linked form'
+    create.id = '_create'
+    create.formdef_slug = 'foo'
+    create.mappings = [
+        Mapping(field_id='0', expression='{% if False %}3{% endif %}'),
+    ]
+    create.parent = wf.possible_status[1]
+    wf.possible_status[1].items.insert(0, create)
+    wf.store()
+
+    source_formdef = FormDef()
+    source_formdef.name = 'Foo'
+    source_formdef.fields = []
+    source_formdef.workflow_id = wf.id
+    source_formdef.store()
+    source_formdef.data_class().wipe()
+
+    formdata = source_formdef.data_class()()
+    formdata.data = {}
+    formdata.just_created()
+    formdata.perform_workflow()
+
+    assert target_formdef.data_class().count() == 1
+    target_formdata = target_formdef.data_class().get(1)
+    assert target_formdata.data == {'0': None}

wcs/fields.py

@@ -2100,7 +2100,7 @@ class ItemField(WidgetField, MapOptionsMixin, ItemFieldMixin):
         return value
 
     def convert_value_from_anything(self, value):
-        if value is None:
+        if not value:
             return None
         value = str(value)
         if self.data_source: