subject:"Re\: \[Django\] #35641\: Pattern matching on model objects"

Re: [Django] #35641: Pattern matching on model objects

2024-07-30 Thread Django

#35641: Pattern matching on model objects
-+-
 Reporter:  jdahlin  |Owner:  (none)
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Comment (by jdahlin):

 Sorry, I got confused, __match_args__ needs to be a tuple and cannot be a
 property, so my suggested implementation above is too simplistic. I real
 one would have to be a bit more involved and generate the values and
 create a tuple inside the models metaclass.
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Re: [Django] #35641: Pattern matching on model objects

2024-07-30 Thread Django

#35641: Pattern matching on model objects
-+-
 Reporter:  jdahlin  |Owner:  (none)
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Description changed by jdahlin:

Old description:

> It would be nice if I could use pattern matching on Django model fields,
> this is especially important in context where I don't know what the model
> is, for example in a global post_save() handler where I want to do some
> specific logic based on a subclass.
>

> {{{#!python
> class Person(Model):
> name = TextField(...)
> age = IntegerField(...)
>
> class Company(Model):
> address = TextField(...)
> }}}
>
> I would then be able to do
> {{{#!python
> @receiver(pre_save)
> def pre_save(sender, instance, ):
># model comes in via signals or some other way, we don't know which
> subclass it is
>match model:
>   # equivalent to isinstance(model, Person) and model.age > 10:
>case Person(age) if age> 10:
> 
>   # equivalent to isinstance(model, Company) and
> model.name.endswith('Street')
>case Company(address) if name.endswith('Street'):
> 
># or just extract and return a value
>case Person(name):
>return name
> }}}
>
> The implementation for this is fairly straight-forward, add this to
> models.Model.
>
> {{{#!python
> @property
> def __match_args__(self) -> tuple[str, ...]:
> return tuple(f.name for f in self._meta.get_fields())
> }}}
>
> Happy to create a PR if this is interesting.

New description:

 It would be nice if I could use pattern matching on Django model fields,
 this is especially important in context where I don't know what the model
 is, for example in a global post_save() handler where I want to do some
 specific logic based on a subclass.


 {{{#!python
 class Person(Model):
 name = TextField(...)
 age = IntegerField(...)

 class Company(Model):
 address = TextField(...)
 }}}

 I would then be able to do
 {{{#!python
 @receiver(pre_save)
 def pre_save(sender, instance, ):
# model comes in via signals or some other way, we don't know which
 subclass it is
match model:
   # equivalent to isinstance(model, Person) and model.age > 10:
case Person(age) if age> 10:
 
   # equivalent to isinstance(model, Company) and
 model.name.endswith('Street')
case Company(address) if name.endswith('Street'):
 
# or just extract and return a value
case Person(name):
return name
 }}}

 Since __match_args__ must be a tuple, the attribute must be generated
 inside a metaclass.

 ~~{{{#!python
 @property
 def __match_args__(self) -> tuple[str, ...]:
 return tuple(f.name for f in self._meta.get_fields())
 }}}~~

 Happy to create a PR if this is interesting.

--
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Django 
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Re: [Django] #35641: Pattern matching on model objects

2024-07-30 Thread Django

#35641: Pattern matching on model objects
-+-
 Reporter:  jdahlin  |Owner:  (none)
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Description changed by jdahlin:

Old description:

> It would be nice if I could use pattern matching on Django model fields,
> this is especially important in context where I don't know what the model
> is, for example in a global post_save() handler where I want to do some
> specific logic based on a subclass.
>

> {{{#!python
> class Person(Model):
> name = TextField(...)
> age = IntegerField(...)
>
> class Company(Model):
> address = TextField(...)
> }}}
>
> I would then be able to do
> {{{#!python
> @receiver(pre_save)
> def pre_save(sender, instance, ):
># model comes in via signals or some other way, we don't know which
> subclass it is
>match model:
>   # equivalent to isinstance(model, Person) and model.age > 10:
>case Person(age) if age> 10:
> 
>   # equivalent to isinstance(model, Company) and
> model.name.endswith('Street')
>case Company(address) if name.endswith('Street'):
> 
># or just extract and return a value
>case Person(name):
>return name
> }}}
>
> Since __match_args__ must be a tuple, the attribute must be generated
> inside a metaclass.
>
> ~~{{{#!python
> @property
> def __match_args__(self) -> tuple[str, ...]:
> return tuple(f.name for f in self._meta.get_fields())
> }}}~~
>
> Happy to create a PR if this is interesting.

New description:

 It would be nice if I could use pattern matching on Django model fields,
 this is especially important in context where I don't know what the model
 is, for example in a global post_save() handler where I want to do some
 specific logic based on a subclass.


 {{{#!python
 class Person(Model):
 name = TextField(...)
 age = IntegerField(...)

 class Company(Model):
 address = TextField(...)
 }}}

 I would then be able to do
 {{{#!python
 @receiver(pre_save)
 def pre_save(sender, instance, ):
# model comes in via signals or some other way, we don't know which
 subclass it is
match model:
   # equivalent to isinstance(model, Person) and model.age > 10:
case Person(age) if age> 10:
 
   # equivalent to isinstance(model, Company) and
 model.name.endswith('Street')
case Company(address) if name.endswith('Street'):
 
# or just extract and return a value
case Person(name):
return name
 }}}

 Happy to create a PR if this is interesting.

--
-- 
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

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Re: [Django] #35641: Pattern matching on model objects

2024-07-30 Thread Django

#35641: Pattern matching on model objects
-+-
 Reporter:  Johan Dahlin |Owner:  (none)
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Comment (by Simon Charette):

 I think we'd have to see a PR and how invasive it is to implement before
 taking a decision here. I personally only see marginal readability gains
 in the example you provided so I'm skeptical that's worth the complexity.
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Ticket URL: 
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Re: [Django] #35641: Pattern matching on model objects

2024-07-30 Thread Django

* resolution: => wontfix
* status: new => closed

Comment:

Hello Johan, welcome to the Django Community! Nice to see you again.

I personally like your proposal, but since Django is a community driven
project, there is a established procedure to request new features which
requires first gathering community consensus so then a ticket can be
accepted. To do that, please consider starting a new conversation on the
[https://forum.djangoproject.com/c/internals/5 Django Forum], where you'll
reach a wider audience and likely get extra feedback.

I'll close the ticket for now, but if there is a community agreement for
the feature request, you are welcome to come back to the ticket and point
to the forum topic, so we can then re-open it. For more details, please
see [https://docs.djangoproject.com/en/stable/internals/contributing/bugs-
and-features/#requesting-features the documented guidelines for requesting
features].

Thanks!
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Ticket URL:
Django
The Web framework for perfectionists with deadlines.

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Re: [Django] #35641: Pattern matching on model objects

Re: [Django] #35641: Pattern matching on model objects

Re: [Django] #35641: Pattern matching on model objects

Re: [Django] #35641: Pattern matching on model objects

Re: [Django] #35641: Pattern matching on model objects

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