Error in select widget when value is noValueToken

[parruc]

BUG

What I did:

I'm using a single select widget on a choice field populated with a staticcatalog vocabulary and I get an error when saving if the value is not compiled and there is another validation error on the page

What I expect to happen:

Save the content even if the selected value is empty

What actually happened:

Got the following error:

zope.location.interfaces.LocationError: zope.location.interfaces.LocationError: (<SelectWidget 'form.widgets.rubrica'>, 'items')

That actually masks this one:

AttributeError: 'NoneType' object has no attribute 'token'

happening inside

> z3c.form-6.0.1-py3.13.egg/z3c/form/browser/select.py(100)items() -> addItem(idx, term, prefix='missing-')

Because term is None when called on MissingValue

What version of Python and Zope/Addons I am using:

python 3.13.3
Zope 5.13
Plone 6.1.2
z3c.form 6.0.1

[parruc]

I tried to come up with a test, but it required too many mockups and I didn’t have time to work on it. However, while attempting to write the test, I dug deeper into the issue and realized that maybe z3c.form isn’t the culprit after all.

From the interface declaration, I understand that getTerm and getTermByToken should raise a LookupError if they are unable to find the required term by token.

# z3c.form-6.0.1-py3.13.egg/z3c/form/interfaces.py (329)

    def getTerm(value):
        """Return an ITitledTokenizedTerm object for the given value

        LookupError is raised if the value isn't in the source
        """

    def getTermByToken(token):
        """Return an ITokenizedTerm for the passed-in token.

        If `token` is not represented in the vocabulary, `LookupError`
        is raised.
        """

It seems that plone.app.vocabularies does not adhere to that interface:

  # plone.app.vocabularies-6.0.2-py3.13.egg/plone/app/vocabularies/catalog.py (596)

    def getTerm(self, value):
        if not isinstance(value, str):
            # here we have a content and fetch the uuid as hex value
            value = IUUID(value)
        query = {"UID": value}
        brains = self.catalog(**query)
        for b in brains:
            return self.createTerm(b, None)

    getTermByToken = getTerm

If no brain matches, None is implicitly returned… but maybe a LookupError should be raised instead?

Having term = None breaks addItem when trying to access term.token

# z3c.form-6.0.1-py3.13.egg/z3c/form/browser/select.py (76)

    def addItem(idx, term, prefix=''):
            selected = self.isSelected(term)
            if selected and term.token in ignored:
                ignored.remove(term.token)
            id = '%s-%s%i' % (self.id, prefix, idx)
            content = term.token
            if zope.schema.interfaces.ITitledTokenizedTerm.providedBy(term):
                content = translate(
                    term.title, context=self.request, default=term.title)
            items.append(
                {'id': id, 'value': term.token, 'content': content,
                 'selected': selected})

So this pull request should probably be closed, and another should be created on 'plone.app.vocabularies' but I’d like a second opinion on this because I'm not really sure if that change can break other things or if this pull request should be kept anyway.

[davisagli]

@parruc I think your analysis is correct. Once there's a PR for plone.app.vocabularies we can run all the Plone tests with that change to see if it causes any other problems.

[parruc]

Created the mentioned issue and made a pull request here:

plone/plone.app.vocabularies#107