Attempting to render/access a SiteMap fails with RenderException caused by

info.magnolia.config.registry.Registry$NoSuchDefinitionException: GoogleSiteMap
	info.magnolia.config.registry.AbstractRegistry.getProvider(AbstractRegistry.java:123)
	info.magnolia.rendering.template.registry.TemplateDefinitionRegistry.getTemplateDefinition(TemplateDefinitionRegistry.java:105)
...
	info.magnolia.cms.filters.MgnlMainFilter.doFilter(MgnlMainFilter.java:94)

To reproduce

Go to https://demoauthor.magnolia-cms.com (or a local bundle), create a sitemap and try to access it.

Source of the problem

When creating or updating a sitemap, the id of the template gets set incorrectly, so no TemplateDefinition is found for it in the template registry.

The app comes with a custom field definition TemplateStaticFieldDefinition that sets the value to google-sitemap:pages/siteMapsConfiguration for (property-) name mgnl:template. A custom converter (see TemplateStaticFieldFactory) used to set the presentation value to the template title and the model value to the template id. Due to changes in UI – source has yet to be determined – the presentation value ends up in the item (see SaveSiteMapAction).

Possible solutions

Due to the field being hidden (setVisible(false) call in field itself) we've found the folloing option. Side note: (Broken template definitions are not validated.)

1. Quickfix: Make converter (com.vaadin.data.util.converter.Converter#convertToPresentation()) return the template id instead of the title.
2. Chosen solution: Completely remove converter; This solution will simplify the field factory.

We should also update potentially broken mgnl:template properties of exisiting sitemaps by replacing GoogleSiteMap with google-sitemap:pages/siteMapsConfiguration.