After struggling with custom value lists I found out a really inconvenient inconsistency. The issue is the following:
When creating a custom value list provider, you need to extend the following class:
Which contains the following property:
String SERVICE = "valuelist.provider";
When reading the following documentation, it will tell me to use valuelistProvider
Although when using the default DynamicDropdown field (org.onehippo.cms.channelmanager.content.documenttype.field.type.DynamicDropdownFieldType) , the following value is used
public static final String VALUELIST_PROVIDER = "valuelistProvider";
So when using a org.onehippo.forge.selection.frontend.plugin.DynamicMultiSelectPlugin, you need to configure the property valuelist.provider, but when using the DynamicDropdown you need to use valuelistProvider.
This took me a while to find out, especially when the difference is so small. So I hope this could change into the same value to make this more convenient in the future. In the mean time, I hope other developers will find this post before having to deep dive into this topic again. Maybe a short time fix would be to include a note into the documentation?
Have a nice day!