In fact, think I would rather see those renamed to BKE_collection_duplicate()/_duplicate_ex().

Am becoming a bit tired of seeing copy used for all kind of different things, would like to keep it for 'basic' regular ID copying, and any more involved code doing some deep-copy and such would then use duplicate instead.

Not related to this patch, but those tree should really be put below 'generic ID API' that are _copy_data() and _make_local(), with an empty line in between...

Naming conventions for bools, something like do_hierarchy and keep_linked e.g. ?

Not implemented, good oportunity to nuke it and replace its only call (in full scene copying) by one to BKE_collection_copy_ex I guess?

That looks more like unrelated cleanup? ;)

Same remark as for collections regarding naming, in fact this is even more critical here since your new copy_ex func is not even used by the copy one. So would rather like to see it named BKE_object_duplicate() imho.

name as well, rather duplicate than copy… And maybe also replace hierarchy with recursive, so that this behavior becomes obvious?

LIB_TAG_DOIT is a RESET_BEFORE_USEflag currently (turning it into a RESET_AFTER_USE is still a boring TODO for some rainy day). So please clean it up *before* any usage, and also after in new code.

Not sure why you cannot move (most of) BKE_collection_copy_ex() logic here, just keeping security checks and final collection sync there, and e.g. pass NULL GHash when you do not want to do recursion in hierarchy? Then you just need to add the parent parameter to this function, and you are done?

Would find it cleaner to have all logic in a same place…

Think that whole block could go into collection_copy_hierarchy()

In fact for the linked guy, I’d rather see it logically reversed, and named something like do_deep_copy or something, because 'linked' behavior should remain default one in general, doing deep-copy being some 'less usual' behavior.

I would rather we do it afterwards. Scene copying is working now, so just remove this and call BKE_collection_duplicate will likely introduce issues.

It is related to making ob const in BKE_copy_ex, since this function was called from a non-const ob function before (object_add_duplicate_internal).
That said I will separate this "cleanup" on its own commit.

Calling BKE_main_id_tag_idcode(bmain, ID_GR, LIB_TAG_DOIT, false); before this function. Maybe you missed that?

Not sure how much more you wanted this integrated in the collection_duplicate_recursive, so I leave to you to do this final cleanup? :)