Dynamics 365 Virtual Entities unsupported field types

Microsoft recently introduced virtual entities into Dynamics 365. This is an easy way (or is it?) to integrate with external system, removing the need for data duplication while having a data model definition.

Check out Jesper Osgaard's posts on the subject at his blog

The documentation is not exactly updated and optimal for virtual entities yet, so I'm going to add this little tidbit into the world of MSDYN365 Customer Engagement. Some of the unsupported options are documented, but I'm adding them as well because they are available in the UI.
And finally, before we jump into the salad, business required doesn't matter at all, because you cannot edit data in virtual entities (yet). That said, you might be able to in the future, so plan ahead will you?

Adding fields to virtual entities

After you've set up a new virtual entity, when you go to create a new field you get the following options as data types

Keys are not supported

Trying to add alternate keys to a virtual entity will give you the normal editing screen, but as soon as you click OK to create the new key you will be presented with the following error

Fields not supported

First off the two types that is selectable, but will give you an error. Calculated and rollup fields. Trying to add that will give you the following errors:

Attribute field type: Calculated is not valid for virtual entity.

Attribute field type: Rollup is not valid for virtual entity.

Multi-Select option set

At first when you start adding the field it looks like everything should work, but that's only because it's the same editing form as for option sets. Trying to save the field will give you an error message, and if you download the log file it says
Attribute data type: multiselectpicklist is not valid for this entity.

Image

Trying to add an image field will generate an error which is much more cryptic. The message is as follows:
Cannot find the object "new_agreementBase" because it does not exist or you do not have permissions.

Seems like there's a missing null check here, so they're trying to access the database and modify the content.

Currency

Trying to add currencies will product the following error in the log file:

Attribute data type: money is not valid for this entity.

This is probably due to currency (or money) is represented by two tables. One which contains the base conversion, and one which contains the value. It seems like something that could be supported in the future, but right now it's isn't.

Customer

Trying to create a customer field will give a somewhat more cryptic error message

For Relationships referencing Virtual Entites, Cascade link type must be No Cascade

The issue here is that customer is a polymorphic field (kind of like an intersect of other fields) of both the account and contact field, and when you add a customer field it's an implicit cascade delete referential from one field to the other. This relationship cannot be edited, and being read-only the virtual entity only supports cascade-only.

It stands to reason that if/when edit options become available this field will be supported as well.

Supported number ranges

All number types are supported like before (except for those applicable for money, obviously), but for those of you who hoped to be able to build bigger/smaller numbers in an external system I have some bad news: it still has the same size limitation as default fields. That goes for both number size and decimal precision.

Wrap up

So there you have it, all the fields that are NOT supported in MSDYN365 v9 as of right now (October 10th 2017). The virtual entity is still quite new, and Microsoft isn't holding your hand every step of the way just yet. Please drop me a line if you experience something different than what I've posted here, and I'll try to keep up to date as things change in the future.

Also, thanks to @rappen for proof reading and providing better explanations