➜
This issue trackerhas been migrated toGitHub, and is currentlyread-only.
For more information, see the GitHub FAQs in the Python's Developer Guide.
Created on2018-03-19 03:30 bystachel, last changed2022-04-11 14:58 byadmin. This issue is nowclosed.
| Pull Requests | |||
|---|---|---|---|
| URL | Status | Linked | Edit |
| PR 6152 | merged | eric.smith,2018-03-20 00:49 | |
| PR 6153 | merged | miss-islington,2018-03-20 01:08 | |
| Messages (8) | |||
|---|---|---|---|
| msg314077 -(view) | Author: Adrian Stachlewski (stachel) | Date: 2018-03-19 03:30 | |
I've tried to declare two classes@dataclassclass Base: __slots__ = ('x',) x: Any@dataclassclass Derived(Base): x: int y: intAs long as I correctly understoodPEP 557 (inheritance part), changing type of variable is possible. This code produce error:TypeError: non-default argument 'y' follows default argument'x' variable in Derived class has changed default from MISSING to member_descriptor and that's the reason of the exception. | |||
| msg314087 -(view) | Author: Eric V. Smith (eric.smith)* | Date: 2018-03-19 08:57 | |
This is the same reason that this fails:class Base: __slots__ = ('x',) x = 3with:ValueError: 'x' in __slots__ conflicts with class variableIn the dataclasses case, the error needs to be improved, and moved to when the base class is being defined. | |||
| msg314090 -(view) | Author: Adrian Stachlewski (stachel) | Date: 2018-03-19 09:14 | |
I don't really get your point. @dataclassclass Base: __slots__ = ('x',) x: AnyThis case is described inPEP 557 as correct, so I don't understand why you want to generate error. Also inheritance without defining slots is correct as stated in data model. In my opinion, member_descriptor should be treated same as MISSING and everything should work correctly. | |||
| msg314091 -(view) | Author: Eric V. Smith (eric.smith)* | Date: 2018-03-19 11:32 | |
My point is that the problem is that after:@dataclassclass Base: __slots__ = ('x',) x: AnyBase.x has a value (it's the member_descriptor for x). That's what's causing the problem that when adding a field to the derived class, it thinks you're adding a field without a default value after one that has a default value.I agree that I could detect this specific case and allow it. My comment about the error message was inaccurate. | |||
| msg314121 -(view) | Author: Adrian Stachlewski (stachel) | Date: 2018-03-19 21:52 | |
There's also another major problem. Because Base.x has value, __init__ is not prepared correctly (member_descriptor is passed as default). @dataclassclass Base: __slots__ = ('x',) x: AnyBase() # No TypeError exceptionFixing this should be quite easy, if you want I can prepare PR. | |||
| msg314122 -(view) | Author: Eric V. Smith (eric.smith)* | Date: 2018-03-19 22:30 | |
Thanks, but I'm already looking at this in the context of a different bug. | |||
| msg314124 -(view) | Author: Eric V. Smith (eric.smith)* | Date: 2018-03-20 01:07 | |
New changeset7389fd935c95b4b6f094312294e703ee0de18719 by Eric V. Smith in branch 'master':bpo-33100: Dataclasses now handles __slots__ and default values correctly. (GH-6152)https://github.com/python/cpython/commit/7389fd935c95b4b6f094312294e703ee0de18719 | |||
| msg314128 -(view) | Author: Eric V. Smith (eric.smith)* | Date: 2018-03-20 01:31 | |
New changeset3d41f482594b6aab12a316202b3c06757262109a by Eric V. Smith (Miss Islington (bot)) in branch '3.7':bpo-33100: Dataclasses now handles __slots__ and default values correctly. (GH-6152) (GH-6153)https://github.com/python/cpython/commit/3d41f482594b6aab12a316202b3c06757262109a | |||
| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:58:58 | admin | set | github: 77281 |
| 2018-03-20 01:39:18 | eric.smith | set | status: open -> closed resolution: fixed stage: patch review -> resolved |
| 2018-03-20 01:31:25 | eric.smith | set | messages: +msg314128 |
| 2018-03-20 01:08:15 | miss-islington | set | pull_requests: +pull_request5911 |
| 2018-03-20 01:07:55 | eric.smith | set | messages: +msg314124 |
| 2018-03-20 00:49:32 | eric.smith | set | keywords: +patch stage: patch review pull_requests: +pull_request5910 |
| 2018-03-19 22:30:01 | eric.smith | set | messages: +msg314122 |
| 2018-03-19 21:52:16 | stachel | set | messages: +msg314121 |
| 2018-03-19 11:32:31 | eric.smith | set | messages: +msg314091 |
| 2018-03-19 09:14:50 | stachel | set | messages: +msg314090 |
| 2018-03-19 08:57:06 | eric.smith | set | messages: +msg314087 |
| 2018-03-19 03:43:05 | rhettinger | set | assignee:eric.smith nosy: +eric.smith |
| 2018-03-19 03:30:15 | stachel | create | |