Custom expression function in sync rule doesn’t return NULL

Some days ago I faced a problem at a customer site with datetime attribute flows.
Users have separation dates as long as they have a limited contract, but when they got an unlimited contract the separation date is removed (NULL in database).

I’ve got a response from a system owner that dates for users with unlimited contract will not be cleared in their system.
First thought was I may be forgot to set the “allow Null on export” flag. But it was set on that attribute which is exported as a string value.

My sync rules custom expression was like this:

DateTimeFormat(SeparationDate,"yyyy-MM-dd") => ContractEndDate

After some investigation I found out that this expression does not return a NULL value if separation date is not set.
Never read that behavior in any documentation if I remember correctly.

So I modified the custom expression a bit like this:


And it works.

The nullString is an empty metaverse attribute on user objects which will never get a value, so it always is NULL.
All my implementation have this empty objects because they are very useful on clearing attributes in data sources when using sync rules.
Beside the nullString attribute I also have the nullReference attribute.

Keep in mind that the Null() function in custom expressions means “do nothing” and does not return a Null value.

Don’t know if this is also relevant to other functions of custom expressions, but it could be.



About Peter Stapf
Senior Consultant Identity and Access MVP (Enterprise Mobility)

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