Vocabulary-related errors with a custom widget

Question

I have two Dexterity content types - Participant & Criterion - the latter of which is used to determine participant inclusion in a project. Criteria are stored on the Participant as a RelationList, however I'd like to replace the default picker widget with a checkbox based one. I've created a custom widget that I'm assigning to the criteria field which displays the correct criteria as checkboxes, but gives me the following error when it validates:

2011-11-04 00:27:26 ERROR Zope.SiteErrorLog 1320380846.610.720672558798 http://192.168.2.128:8080/ctcc/Trials/trial1/sites/site1/++add++ctcc.Participant
Traceback (innermost last):
  Module ZPublisher.Publish, line 126, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 46, in call_object
  Module plone.z3cform.layout, line 70, in __call__
  Module plone.z3cform.layout, line 54, in update
  Module plone.z3cform.fieldsets.extensible, line 59, in update
  Module plone.z3cform.patch, line 30, in GroupForm_update
  Module z3c.form.group, line 125, in update
  Module z3c.form.form, line 134, in updateWidgets
  Module z3c.form.field, line 275, in update
  Module z3c.form.browser.checkbox, line 44, in update
  Module z3c.form.browser.widget, line 70, in update
  Module z3c.form.widget, line 200, in update
  Module z3c.form.widget, line 84, in update
  Module z3c.form.widget, line 216, in extract
AttributeError: 'list' object has no attribute 'getTermByToken'

I have defined the widget like so:

class ICriteriaListingWidget(Interface):
    """Marker interface for the criteria listing widget"""

class CriteriaSelectionWidget(CheckBoxWidget):
    implements(ICriteriaListingWidget)
    klass = u'criteria-listing-widget'
    input_template = ViewPageTemplateFile('criteria_listing_input.pt')
    display_template = ViewPageTemplateFile('criteria_listing_display.pt')

    @property
    def terms(self):
        catalog = getToolByName(self.context, 'portal_catalog')
        content = catalog(
            portal_type='ctcc.Criterion',
        )
        return [SimpleTerm(x.id, x, title=x.Title) for x in content]

@adapter(IRelationList, IFormLayer)
@implementer(IFieldWidget)
def CriteriaListingWidget(field, request):
    return FieldWidget(field, CriteriaSelectionWidget(request))

Then on the Participant Dexterity type, the field is:

form.widget(criteria=CriteriaListingWidget)
criteria = RelationList(
    title = _(u'Inclusion Criteria'),
    description = _(u'The participant criteria evaluated against for inclusion'),
    value_type = RelationChoice(
        source = ObjPathSourceBinder(
            object_provides = ICriterion.__identifier__,
        ),
    ),
    default = [],
    required = False,
)

Given the nature of the error, I replaced the ObjPathSourceBinder source with a custom Vocabulary for criteria hoping it would return objects with the correct interface, but I'm seeing the exact same errors using that solution.

UPDATE: I've wrapped the terms list in a SimpleVocabulary as suggested but it just shifts the problem along. Note that the error is now occurring in kss_z3cform_inline_validation.

2011-11-06 19:24:36 ERROR Zope.SiteErrorLog 1320625476.430.209960132592 http://192.168.2.128:8080/ctcc/Trials/trial1/sites/site1/kss_z3cform_inline_validation
Traceback (innermost last):
  Module ZPublisher.Publish, line 126, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 46, in call_object
  Module <wrapper>, line 5, in wrapper
  Module kss.core.actionwrapper, line 236, in apply
  Module plone.app.z3cform.kss.validation, line 51, in validate_input
  Module z3c.form.group, line 92, in extractData
  Module z3c.form.form, line 145, in extractData
  Module z3c.form.field, line 301, in extract
  Module z3c.form.converter, line 311, in toFieldValue
AttributeError: 'SimpleVocabulary' object has no attribute 'getValue'
2011-11-06 19:24:36 ERROR plone.transformchain Unexpected error whilst trying to apply transform chain

Answer 1

I'm not sure if this counts as an answer per se but I ended up avoiding the need for a custom widget by creating custom Source & SourceBinder objects.

class CTCCSource(object):
    implements(IVocabularyTokenized)

    container    = None
    content_type = None

    def __init__(self, context):
        self.context = context
        container_path = self._container_path(context)
        self.catalog = getToolByName(context, 'portal_catalog')
        self.intid_utility = getUtility(IIntIds)
        self.content = [i.getObject() for i in self.catalog(portal_type=self.content_type, path={'query': container_path})]

    def _container_path(self, context):
        physical_path = list(context.getPhysicalPath())
        trial_path = physical_path[:physical_path.index('sites')]
        criteria_path = trial_path + [self.container]
        return '/'.join(criteria_path)

    def __contains__(self, term):
        return term in self.content

    def __iter__(self):
        for crit in self.content:
            yield SimpleTerm(crit, self.intid_utility.getId(crit), crit.Title)

    def __len__(self):
        return len(self.content)

    def getTerm(self, obj):
        return SimpleVocabulary.createTerm(
            obj, self.intid_utility.getId(obj), obj.Title()
        )

    def getTermByToken(self, value):
        return self.getTerm(self.intid_utility.getObject(int(value)))

class CTCCSourceBinder(object):
    implements(IContextSourceBinder)
    source = None

    def __init__(self, **kw):
        pass

    def __call__(self, context):
        return self.source(context)

This allowed me to produce form checkbox fields from content contained within the current context, adding references to the chosen options into a RelatedList.

Answer 2

You will need to return a vocabulary object, not a list:

from zope.schema.vocabulary import SimpleTerm, SimpleVocabulary

# ...

class CriteriaSelectionWidget(CheckBoxWidget):
    # ...

    @property
    def terms(self):
        catalog = getToolByName(self.context, 'portal_catalog')
        content = catalog(
            portal_type='ctcc.Criterion',
        )
        return SimpleVocabulary([SimpleTerm(x.id, x, title=x.Title) for x in content])

The SimpleVocabulary class implements the correct methods for this case.