To use the full power of the RelationWidget in Plone 5, you can set some of the pattern_options, which are described in the link Mockup docs.
If you use a ReleationField, you usually want to browse thru all objects in the database, but only allow to select specific portal_types.
The pattern relateditems which is used by the RelatedItemsFieldWidget, has options to configure this by setting the selectableTypes list (array).
You can pass the patter_options argument to the widget configuration, with plone.autoform.directives like this:
directives.widget(
'location',
RelatedItemsFieldWidget,
pattern_options={'selectableTypes': ['location']},
)
locations = RelationList(
title=_(u'Locations'),
value_type=RelationChoice(
title=_(u'Related'),
source=CatalogSource(),
),
required=False,
)
This will update the pattern_options with your provided config.
The same way you can add more confgiuration settings for the pattern, like the basePath for example.
