No error when referencing unset relationship object property
I've been writing ObjectScript for a long time and was a little surprised by this behavior so I'd like to understand what is going on.
I was doing a peer review on some source which had roughly the equivalent of the following line:
Set myRecord = ##class(MyObj.Record).%OpenId(id) Set emailList = previousEmails_","_myRecord.RecordGroup.EmailList
I flagged it for further testing because the code didn't check if RecordGroup was set and I knew that not all records were part of a Group so I was expecting that in cases where it wasn't set this line should throw an <INVALID OREF>
However, it turns out that I had forgotten that in the MyObj.Record class, RecordGroup is actually a one:many relationship:
Relationship RecordGroup As MyObj.MyGroup [ Cardinality = one, Inverse = Records ];
This results in the behavior that I didn't expect .... when there is no relationship set up, myRecord.RecordGroup.EmailList returns "" and not an error. In fact, myRecord.RecordGroup.PropertyNotEvenDefinedInMyGroupClassDef also returns "".
Can anyone explain this behavior? I am testing on 2016.1.