Question

I’m using a form where I want to have the required field missing error on many fields depending on the value of one other field.

The use case: the use have to choose between two shipping mode (postale or print). if postale is choosen but fields about address has not been filled I want to raise the error.

Here is some code

class ILivraisonForm(interface.Interface):
    livraison = schema.Choice(title=_(u"Mode de livraison"),
                              vocabulary=vocabulary.livraison)

    livraison_civility = schema.Choice(title=_(u"Civility (livraison)"),
                                       vocabulary=userdata.gender_vocabulary,
                                       required=False)
    livraison_name = schema.TextLine(title=_(u"Name (livraison)"),
                                        required=False)
    livraison_firstname = schema.TextLine(title=_(u"Firstname (livraison)"),
                                        required=False)
    livraison_add1 = schema.TextLine(title=_(u"Address line 1 (livraison)"),
                                        required=False)
    livraison_add2 = schema.TextLine(title=_(u"Address line 2 (livraison)"),
                                        required=False)
    livraison_pc = schema.TextLine(title=_(u"Postal code (livraison)"),
                                        required=False)
    livraison_city = schema.TextLine(title=_(u"City (livraison)"),
                                        required=False)

    livraison_phone = schema.TextLine(title=_(u"Phone"),
                                        required=False)

    accepted = schema.Bool(title=_(u"Accept CGV"),
                           description=_(u"Click here to read the CGV"),
                           required=True)


class LivraisonForm(form.Form):
    fields = field.Fields(ILivraisonForm)

    @button.buttonAndHandler(_(u"Valider"))
    def handleApply(self, action):
        data, errors = self.extractData()
        message = IStatusMessage(self.request)
        if errors:
            self.status = _(u"Please fix errors")
            return
        if not data['accepted']:
            self.status = _(u'You must accept')
            raise WidgetActionExecutionError('accepted',
                                     interface.Invalid(_(u'You must accept')))

        if data['livraison'] == 'mail' \
          and ( not data['livraison_name'] or not data['livraison_firstname'] \
          or not data['livraison_add1'] or not data['livraison_pc'] \
          or not data['livraison_city']):
            self.status = _(u'You must add your postal address')
            raise ???

Answer 1

You don’t need to raise anything; just add a return instead of a raise right where you are.

In addition, you can set error messages on individual widgets in an action handler, provided you create a zope.schema.ValidationError subclass:

from zope.schema import ValidationError

class AddressMissing(ValidationError):
    __doc__ = _(u'error_noaddress', u'Please provide an address')

and then in the handler:

from z3c.form.interfaces import IErrorViewSnippet
from zope import component

def handleApply(self, action):
    # ....

    widget = self.widgets['livraison_add1']
    error = component.getMultiAdapter(
        (AddressMissing(), self.request, widget, widget.field,
         self, self.context), interfaces.IErrorViewSnippet)
    error.update()
    widget.error = error

You can do this for all affected widgets.

Alternatively, you can have this handled using an invariant:

from zope.interface import invariant, Invalid

class ILivraisonForm(interface.Interface):
    # ....

    @invariant
    def validatePostalAddress(data):
        if data.livraison. != 'mail':
            return
        for field in ('name', 'firstname', 'add1', 'pc', 'city'):
            if not data['livraison_' + field]:
                raise Invalid(_(u'error_noaddress', u'Please provide an address'))

and the error will be set when you call self.extractData().