addLink creates a new Set for unloaded collections.

[jamoore]

If a collection is unloaded ( Object.typeLinks ) and a new item is linked (e.g.
Project.addDataset( dataset ) ), then the addTYPE method initializes the
typeLinks set to new HashSet?();

This will thoroughly confuse the backend.

This needs to either:

1. Throw an exception.
2. Intialize the field and set it to "filtered". The backend will need to be changed to find the new member.

---

In resurrect, this was leading to the "only one addable user" bug. Basically doing,

 for ( User user : users ) 
 { 
   group = server.getGroup()
   user.linkGroup( group )
   server.save( user )
 } 

would only store the last user, because the serialized version of group from the
server had a nulled out users (Experimenters) java.util.Set.

Originally : ​http://bugs.openmicroscopy.org.uk/show_bug.cgi?id=666

[jmoore]

r662 removed the problem spots, basically calls of the form:

    if ( set == null )
    {
       set = new HashSet();
    }
    modifySet( set );

are now:

    if ( set == null )
      throw new ApiUsageException("Please update");

    modifySet( set );

This will most certainly cause exceptions where there were none before, but will prevent corrupt data (especially spurious deletes!)