[Pulp-dev] Required fields for models at the DB level

Tatiana Tereshchenko ttereshc at redhat.com
Tue Dec 10 08:39:06 UTC 2019

+1 to have additional serializer for validation content fields and use
current serializers for upload case
+1 to validate during sync

On Fri, Dec 6, 2019 at 8:31 PM David Davis <daviddavis at redhat.com> wrote:

> I talked to @ttereshc this afternoon and a couple questions came up.
> First, in pulp_rpm we have a PackageSerializer[0] that handles creating
> and displaying packages. The problem is that the package field values are
> derived from the artifact and not the user so most fields are readonly and
> not required. I'm imagining we'll have to split this serializer in two (ie
> a PackageSerializer and a PackageUploadSerializer) in order to use it to
> validate package data. Does that make sense or is there a better way?
> Secondly, I don't think we're validating data during sync. What if a user
> syncs data from a remote that has bad data? I think we'll need to have the
> stages somehow use serializers as well? If others agree, I can file an
> issue.
> [0]
> https://github.com/pulp/pulp_rpm/blob/326d189bbae9267d59282d62ada1fa36467a2d8f/pulp_rpm/app/serializers.py#L69
> David
> On Thu, Dec 5, 2019 at 6:32 AM David Davis <daviddavis at redhat.com> wrote:
>> This makes sense to me. I wonder if we should document what you've
>> outlined in the plugin writers guide? If so, then maybe we should repurpose
>> 5828?
>> David
>> On Tue, Dec 3, 2019 at 12:14 PM Brian Bouterse <bmbouter at redhat.com>
>> wrote:
>>> After some IRC discussion during open floor, I think the consensus is
>>> that we should not have BaseModel call full_clean(). Plugin writers doing a
>>> lot of object creation without involving DRF serializers should call
>>> full_clean() either in application code or their specific model's save()
>>> method. Here's some recap about the motivations for this:
>>> * By having full_clean() called with all model save it gives Pulp "two
>>> validation layers" when there only needs to be one. DRF's validation layer
>>> is the serializer, and it isn't prepared to do error handling from a
>>> "second" layer. This is partly an echo of the concerns from Tom Christie's
>>> writing.
>>> * DRF is primarily designed to have data flow through its serializers.
>>> This issue is more problematic in cases where data is not flowing through
>>> the serializer. Thus we should try to include the serializer whenever
>>> possible.
>>> * If we cannot include the serializer, those are cases where we would
>>> specifically benefit from calling full_clean manually.
>>> Other thoughts and concerns are welcome. If nothing major comes up then
>>> we can close https://pulp.plan.io/issues/5828 as WONTFIX.
>>> On Mon, Dec 2, 2019 at 6:52 PM Simon Baatz <gmbnomis at gmail.com> wrote:
>>>> On Mon, Dec 02, 2019 at 03:53:06PM -0500, Brian Bouterse wrote:
>>>> >    If anyone has concerns with us enabling Model validation by
>>>> default on
>>>> >    all models please let us know soon.
>>>> I don't know (yet) if I have concerns, but DRF seems to have, see
>>>> https://www.django-rest-framework.org/community/3.0-announcement/#differences-between-modelserializer-validation-and-modelform
>>>> According to DRF's design, all validation logic should be at one
>>>> place, which is the serializer.  This seems to be a controversial
>>>> issue, see e.g.
>>>> https://github.com/encode/django-rest-framework/issues/3144.  From
>>>> that issue:
>>>> What happens in the case where in your models you are forcing a
>>>> full_clean (perhaps by including it in the save method)?  Will
>>>> serializers know how to handle an exception from an explicit
>>>> full_clean?
>>>> And Tom Christie's answer:
>>>> I'd recommend that application level validation should generally
>>>> happen prior to save, not during it.  Personally I'd avoid
>>>> full_clean, and instead ensure that state changing operations on
>>>> model instances are only ever made via method calls that can provide
>>>> a boundary that ensures that only valid state changes may ever be
>>>> made by the rest of the application.
>>>> We need to be aware that we are leaving the path recommended by DRF
>>>> if we implement this proposal and mix Django validation and DRF
>>>> validation.  Unfortunately, I don't know what the alternative is.
>>>> Using DRF serializers to construct all model instances looks clumsy
>>>> when it comes to relations.
>>>> _______________________________________________
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