Hello everyone,

In the case of multi-site use, when defining rules such as "maxissueqty" or "patron_maxissueqty", for example, defining a value and then deleting it will allow the basic value to be kept but empty.

As a result, certain code checks based on the rule definition rather than its value may produce unwanted behavior. I want to make sure with this bz that the "can_be_blank" setting could solve this kind of behavior.

Here's a use case: 

For site A, no rule has ever been added to the "Default checkout, hold and return policy" table.

For site B patron_maxissueqty was set to "5", then deleted, and is now set to empty "".

Perform a checkout from site A to a borrower from site C will cause a pop-up with the possibility of forcing the message "This patron can't check out this item per library circulation policy.
No circulation rule is defined for this patron and itemtype combination", whereas the same borrower will be able to obtain an issue without a pop-up for a document linked to site B since the rule is present, the check being based on its presence and not its value.

I therefore wonder whether a list of additional rules could contain the "can_be_blank" parameter introduced by bug 26529 in order to avoid this kind of behavior.