zope.formlib does not correctly validate invariants with fields from a base interface.

[Sebastian Wehrmann]

Example:

>>> import zope.interface
>>> import zope.schema

>>> class IBase(zope.interface.Interface):
... title = zope.schema.TextLine(
... title=u"Title",
... required=False)

>>> class ISub(IBase):
... sub_title = zope.schema.TextLine(
... title=u"Subtitle",
... required=False)
...
... @zope.interface.invariant
... def title_or_subtitle(obj):
... if not (obj.title or obj.sub_title):
... raise zope.interface.Invalid(
... u"Set either title or subtitle.")

When validating an object (using zope.formlib.form.checkInvariants), which implements ISub, it's not possible to access the title attribute inside the "title_or_subtitle" invariant checker method. It's explicitly filtered out, which means, that only those schema attributes, defined on the ISub interface, are available.

Is there any reason for this behavior? There is no test for this behavior.

Suggestion:

If there is no specific reason for this behavior, the invariant should get all the form field data from the request.

[Sebastian Wehrmann (sw-gocept)]

This bug was already fixed in zope.formlib 3.4.0 r69738 by srichter. Unfortunately, Zope 2.10 uses an older version. In Zope 2.11, the bug is fixed.