Re: [Django] #35393: InlineAdmin's are not possible with an editable UUIDField as primary key. (was: InlineAdmin's are *not* possible with an *editable* UUIDField as primary key.)

[Django]

#35393: InlineAdmin's are not possible with an editable UUIDField as primary key.
-------------------------------------+-------------------------------------
Reporter: Willem Van Onsem | Owner: Willem
| Van Onsem
Type: Bug | Status: assigned
Component: contrib.admin | Version: 5.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 1 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Sarah Boyce):

* needs_tests: 0 => 1
* owner: nobody => Willem Van Onsem
* stage: Unreviewed => Accepted
* status: new => assigned
* summary:
InlineAdmin's are *not* possible with an *editable* UUIDField as
primary key.
=>
InlineAdmin's are not possible with an editable UUIDField as primary
key.


Old description:

> This issue was reported on [https://stackoverflow.com/a/78362210/67579
> StackOverflow]: if we have a model with an **editable** primary key that
> is **not** an `AutoField`, the editing of inlines fails.
>
> This is because then the hidden field to "backlink" to the original item
> fails: there is no `<input type="hidden" id="id_child_set-0-id"
> name="child_set-0-id"> in the formsets, so no instances are attached to
> the forms of the formset. At best this would thus create new instances,
> at worst, it will in case of the UUID just fail to edit the inline
> objects and thus reject the entire form(set) and therefore reject the
> edit of the object in general.
>
> The steps to reproduce these are using models:
>
> {{{
> class Parent(models.Model):
> name = models.CharField(max_length=128)
>
> class Child(models.Model):
> id = models.UUIDField(primary_key=True, default=uuid.uuid4)
> name = models.CharField(max_length=128)
> }}}
>
> and then work with an admin:
>
> {{{
> class ChildInline(admin.TabularInline):
> model = Child
> exclude = ("id",) # important
> extra = 1
> verbose_name = "Subexample"
> show_change_link = True
>
> @admin.register(Parent)
> class ParentAdmin(admin.ModelAdmin):
> search_fields = ("name", )
> inlines = [ChildInline,]
> }}}
>
> An easy workaround is to mark the `id` field of the `Child` as
> `editable=False`, which will resolve the issue. But it is not said that
> the UUID should *never* be editable, it is for example possible to
> exclude that for the inline, but then use it for another `ModelAdmin`,
> perhaps to duplicate to another UUID, or just use another primary key
> field altogether.
>
> The fix turned out to be quite minimal: just ensure that the primary key
> field is added, so in the `helpers.py`, for the `InlineAdminForm`, we
> use:
>
> {{{
> def needs_explicit_pk_field(self):
> return (
> # Auto fields are editable, so check for auto or non-editable
> pk.
> self.form._meta.model._meta.auto_field
> or not self.form._meta.model._meta.pk.editable
> or self.form._meta.model._meta.pk.name in
> (self.form._meta.exclude or ())
> or
> # Also search any parents for an auto field. (The pk info is
> # propagated to child models so that does not need to be
> checked
> # in parents.)
> any(
> parent._meta.auto_field or not
> parent._meta.model._meta.pk.editable
> for parent in
> self.form._meta.model._meta.get_parent_list()
> )
> )
> }}}

New description:

This issue was reported on [https://stackoverflow.com/a/78362210/67579
StackOverflow]: if we have a model with an **editable** primary key that
is **not** an `AutoField`, the editing of inlines fails.

This is because then the hidden field to "backlink" to the original item
fails: there is no `<input type="hidden" id="id_child_set-0-id"
name="child_set-0-id"> in the formsets, so no instances are attached to
the forms of the formset. At best this would thus create new instances, at
worst, it will in case of the UUID just fail to edit the inline objects
and thus reject the entire form(set) and therefore reject the edit of the
object in general.

The steps to reproduce these are using models:

{{{
class Parent(models.Model):
name = models.CharField(max_length=128)

class Child(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4)
name = models.CharField(max_length=128)
parent = models.ForeignKey(Parent, on_delete=models.CASCADE)
}}}

and then work with an admin:

{{{
class ChildInline(admin.TabularInline):
model = Child
exclude = ("id",) # important
extra = 1
verbose_name = "Subexample"
show_change_link = True

@admin.register(Parent)
class ParentAdmin(admin.ModelAdmin):
search_fields = ("name", )
inlines = [ChildInline,]
}}}

An easy workaround is to mark the `id` field of the `Child` as
`editable=False`, which will resolve the issue. But it is not said that
the UUID should *never* be editable, it is for example possible to exclude
that for the inline, but then use it for another `ModelAdmin`, perhaps to
duplicate to another UUID, or just use another primary key field
altogether.

The fix turned out to be quite minimal: just ensure that the primary key
field is added, so in the `helpers.py`, for the `InlineAdminForm`, we use:

{{{
def needs_explicit_pk_field(self):
return (
# Auto fields are editable, so check for auto or non-editable
pk.
self.form._meta.model._meta.auto_field
or not self.form._meta.model._meta.pk.editable
or self.form._meta.model._meta.pk.name in
(self.form._meta.exclude or ())
or
# Also search any parents for an auto field. (The pk info is
# propagated to child models so that does not need to be
checked
# in parents.)
any(
parent._meta.auto_field or not
parent._meta.model._meta.pk.editable
for parent in
self.form._meta.model._meta.get_parent_list()
)
)
}}}

--
Comment:

Thank you for the report Willem!
Replicated on main and can see your patch resolves the issue (thank you
for providing that). This just needs a test to be accepted 👍
--
Ticket URL: <https://code.djangoproject.com/ticket/35393#comment:1>
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