Using the provided ModelAdmin it creates a new version even when there are errors

[rasca]

You clone the object in get_object before the forms validation take place.

I think the correct place to do this would be in save_model() taking into consideration that it also affects save_related().

[boydjohnson]

I was able to confirm with a field that does the validation in the Python like EmailField, that cloning happens even though errors happen. @rasca, I think you are right that the cloning should happen in save_model. The below seemed to work, but I don't have time to fully test it out.

def save_model(self, request, obj, form, change):
    if obj and obj.is_latest and 'will_not_clone' not in request.path:
        obj = obj.clone()
    super(VersionedAdmin, self).save_model(request, obj, form, change)

[rasca]

I don't think that solution will work.
You need to think about the m2m fields and the inline formsets that are saved in the save_related().

In the upcoming 1.9 cloning the object in save_model() and assigning it to form.instance and the formsets instances will work, but in 1.8 and previous versions it will not work, because the way in which form.save_m2m is created (when calling form.save(commit=False)) before validating the inlines takes places.

[rasca]

I think I found a solution for 1.8 and earlier:

    def save_model(self, request, obj, form, change):
        if change:
            obj = obj.clone()
            form.instance = obj
            form.save(commit=False)  # trigger save_instance() and update save_m2m

What do you think? We should also update each formset.instace to the cloned obj in save_related().

[boydjohnson]

@rasca Sorry for the delay, when I ran that code it saves the previous object with the updated (cloned) information, so a City named Northfield gets cloned and renamed to Demascus then they both are Demascus.

[rasca]

Yes.. I ended up using this code:

    def save_model(self, request, obj, form, change):
        if change:
            fresh = obj._meta.model.objects.as_of().get(pk=obj.pk)
            new = fresh.clone()
            obj.version_start_date = new.version_start_date
            obj.save()
            form.instance = obj
            form.save(commit=False)  # trigger save_instance() and update save_m2m
        else:
            obj.save()

Though it takes two additional queries and messes with version_start_date manually.