FIX: Duplicating many_many relationships looses the extra fields (fixes #7973)

[UndefinedOffset]

Fixes issue when you duplicate a DataObject with a many_many relationship with extra fields defined for the relationship extra fields are lost due to how DataObject::duplicateManyManyRelations() and DataObject::duplicateRelations() function. In short when the new items are added to the many_many relationship the extra fields are not included or even retrieved when DataObject::duplicateRelations() adds the item to the list. This issue also seems to affect 4.0 but the fix required would be slightly different see #7973 for details.

[dhensby]

This needs to go into 3, I'm afraid

[dhensby]

If you can find a way of patching duplicateRelations without changing the API surface, then it could make a patch release.

[dhensby]

I reckon you can add a new condition to duplicateRelations which was:

if ($relations instanceof ManyManyList) and then use your logic to populate extra data (line 589)

[UndefinedOffset]

Ya that would make sense, let me give it a shot and I'll update in a bit.

[UndefinedOffset]

@dhensby There hows that look? Also should we back port this to 3.5 too or just for 3.6 and another solution for 4.0?

[UndefinedOffset]

Not sure why the PGSQL test failed... it should have worked my local copy with postgres 9.3 and SilverStripe 3.6.5 :S passed

[kinglozzer]

@UndefinedOffset Try adding a sort, I seem to remember PostgreSQL having issues with inconsistent result ordering if you don’t provide one...

[dhensby]

It looks good to me, let's rebase onto 3.5 :)

[UndefinedOffset]

Will do and I have a branch for 4.0 I'll open a pull for that too https://github.com/webbuilders-group/silverstripe-framework/tree/duplicate-many-many-fix-4-0