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

David Davis daviddavis at redhat.com
Fri Dec 6 19:28:36 UTC 2019


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.
>>>
>>> _______________________________________________
>> Pulp-dev mailing list
>> Pulp-dev at redhat.com
>> https://www.redhat.com/mailman/listinfo/pulp-dev
>>
>
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