Widget: Allow passing more invoice data fields (#4162)

doc/user/events/widget.rst

@@ -339,9 +339,9 @@ Currently, the following attributes are understood by pretix itself:
   ``data-attendee-name``, which will pre-fill the last part of the name, whatever that is.
 
 * ``data-invoice-address-FIELD`` will  pre-fill the corresponding field of the invoice address. Possible values for
-  ``FIELD`` are ``company``, ``street``, ``zipcode``, ``city`` and ``country``, as well as fields specified by the
+  ``FIELD`` are ``company``, ``street``, ``zipcode``, ``city``, ``country``, ``internal-reference``, ``vat-id``, and
-  naming scheme such as ``name-title`` or ``name-given-name`` (see above). ``country`` expects a two-character
+  ``custom-field``, as well as fields specified by the naming scheme such as ``name-title`` or ``name-given-name``
-  country code.
+  (see above). ``country`` expects a two-character country code.
 
 * If ``data-fix="true"`` is given, the user will not be able to change the other given values later. This currently
   only works for the order email address as well as the invoice address. Attendee-level fields and questions can

src/pretix/base/forms/questions.py

@@ -1171,7 +1171,7 @@ class BaseInvoiceAddressForm(forms.ModelForm):
                     self.instance.vat_id_validated = False
                     messages.warning(self.request, e.message)
                 else:
-                    raise ValidationError(e.message)
+                    raise ValidationError({"vat_id": e.message})
             except VATIDTemporaryError as e:
                 self.instance.vat_id_validated = False
                 if self.request and self.vat_warning:

src/pretix/presale/checkoutflow.py

@@ -827,6 +827,9 @@ class QuestionsStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
                 'zipcode': wd.get('invoice-address-zipcode', ''),
                 'city': wd.get('invoice-address-city', ''),
                 'country': wd.get('invoice-address-country', ''),
+                'internal_reference': wd.get('invoice-address-internal-reference', ''),
+                'custom_field': wd.get('invoice-address-custom-field', ''),
+                'vat_id': wd.get('invoice-address-vat-id', ''),
             }
         else:
             wd_initial = {
@@ -893,6 +896,15 @@ class QuestionsStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
         if failed:
             messages.error(request,
                            _("We had difficulties processing your input. Please review the errors below."))
+            if "vat_id" in self.invoice_form.errors:
+                # If an invalid VAT ID was given through the widget together with data-fix="true", let's un-block
+                # the field to prevent a deadlock.
+                widget_data = self.cart_session.get('widget_data', {})
+                if "invoice-address-vat-id" in widget_data:
+                    vat_id = widget_data.pop("invoice-address-vat-id", None)
+                    self.invoice_form.data["vat_id"] = vat_id
+                    self.invoice_form.fields["vat_id"].disabled = False
+                    self.cart_session['widget_data'] = widget_data
             return self.render()
         self.cart_session['email'] = self.contact_form.cleaned_data['email']
         d = dict(self.contact_form.cleaned_data)