PEP xxx: Inner Fields Annotations #3326

UltimateLobster · 2023-09-01T11:39:08Z

Appologies for the long time, as discussed in https://discuss.python.org/t/26527, I created a PEP for this suggestion.

I tried to follow the guidelines but this is my first time writing a PEP, so I'm sorry if some things do not quite follow the conventions.

Basic requirements (all PEP Types)

Standards Track requirements

📚 Documentation preview 📚: https://pep-previews--3326.org.readthedocs.build/pep-0728/

AA-Turner · 2023-09-01T11:41:11Z

pep-0728.rst

@@ -0,0 +1,322 @@
+PEP: 728
+Title: Inner Fields Annotations


Could you be a bit more specific with this title? Before reading the PEP I had no idea what "Inner Fields Annotations" meant.

AA-Turner · 2023-09-01T11:41:35Z

pep-0728.rst

+PEP: 728
+Title: Inner Fields Annotations
+Author: Nir Schulman <[email protected]>
+Sponsor: Jelle Zijlstra <[email protected]>


ping @JelleZijlstra for confirmation of sponsorship

Sorry, but I am not sponsoring this PEP at the moment. I already have four open PEPs (696, 702, 724, 727), that feels like too much. I can think about sponsoring more when a few of the others are done.

I see. In that case I'll wait and in the meantime address the rest of the comments (and in general try to improve the idea).

@AA-Turner Does this mean this PR should be closed for now or should it stay open with an appropriate label?

@UltimateLobster I would suggest that you revisit the Discourse thread and see if another core developer interested in typing would sponsor this proposal. I'll close this PR for now so that we're aware that the PEP number isn't reserved, though still happy to discuss any of the comments I made in review.

A

Just to set expectations, I don't know whether I'd be willing to sponsor the PEP if I had fewer open PEPs; I'd have to think more about whether I think this is a good direction to go into. I'd also prefer to see more evidence of the feasibility of the idea (e.g., buy-in from type checker maintainers, ideally a prototype implementation).

AA-Turner · 2023-09-01T11:42:58Z

pep-0728.rst

Please wrap to 80 columns per PEP 1

AA-Turner · 2023-09-01T11:43:11Z

pep-0728.rst

+==========
+Consider the following example:
+
+.. code-block:: py


Suggested change

.. code-block:: py

.. code-block:: python

AA-Turner · 2023-09-01T11:43:21Z

pep-0728.rst

+
+The latter problem can be solved using ``typing.overload``:
+
+.. code-block:: py


Suggested change

.. code-block:: py

.. code-block:: python

AA-Turner · 2023-09-01T11:45:37Z

pep-0728.rst

+the type of ``obj['x']``. These types would have the same meaning for all python objects (Whether working with TypedDicts or
+dataclasses). It would also allow referring to fields of objects containing both attributes and items:
+
+.. code-block:: py


Suggested change

.. code-block:: py

.. code-block:: python

AA-Turner · 2023-09-01T11:45:43Z

pep-0728.rst

+Should __annotations__ be used as the reference table for fields?
+''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''


Suggested change

Should __annotations__ be used as the reference table for fields?

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Should __annotations__ be used as the reference table for fields?

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

AA-Turner · 2023-09-01T11:45:51Z

pep-0728.rst

+Naming
+''''''


Suggested change

Naming

''''''

Naming

''''''

AA-Turner · 2023-09-01T11:46:11Z

pep-0728.rst

+Copyright
+=========
+
+This document is placed in the public domain or under the CC0-1.0-Universal license, whichever is more permissive.


Suggested change

This document is placed in the public domain or under the CC0-1.0-Universal license, whichever is more permissive.

This document is placed in the public domain or under the

CC0-1.0-Universal license, whichever is more permissive.

AA-Turner · 2023-09-01T11:46:31Z

pep-0728.rst

+    func("something else")
+
+
+


Suggested change

AA-Turner · 2023-09-01T11:47:53Z

pep-0728.rst

+Title: Inner Fields Annotations
+Author: Nir Schulman <[email protected]>
+Sponsor: Jelle Zijlstra <[email protected]>
+Discussions-To: https://discuss.python.org/t/26527


This link should go into Post-History; a new thread should be created for PEP 728 just before this PR is merged

AA-Turner · 2023-09-01T11:48:34Z

pep-0728.rst

+========
+
+This PEP specifies a way for annotations to reference the field types of other complex objects. This include the field
+names and types objects with static layout such as dataclasses (or dataclass-like objects), TypedDicts and NamedTuples.


Suggested change

names and types objects with static layout such as dataclasses (or dataclass-like objects), TypedDicts and NamedTuples.

names and types objects with static layout such as dataclasses (or dataclass-like objects), :py:class:`~typing.TypedDict`s and :py:class:`~typing.NamedTuple`s.

AA-Turner · 2023-09-01T11:53:56Z

@UltimateLobster I've added the new PEP checklist to the PR body, please may you go through it and fill in as appropriate?

A

Jackenmen · 2023-09-02T01:09:32Z

pep-0728.rst

+        bar: int
+        baz: str
+
+    bar: TypeAlias = Literal['baz']


Should this use the type parameter syntax since TypeAlias is deprecated(-ish)? They technically don't do the same thing at runtime but I'm guessing both are supposed to work the same within the context of this PEP's new typing constructs.

AA-Turner · 2023-09-02T05:57:06Z

Closing per discussion (no sponsor)

A

Kludex · 2023-09-06T12:19:43Z

Just to set expectations, I don't know whether I'd be willing to sponsor the PEP if I had fewer open PEPs; I'd have to think more about whether I think this is a good direction to go into. I'd also prefer to see more evidence of the feasibility of the idea (e.g., buy-in from type checker maintainers, ideally a prototype implementation).

I know you didn't mean for other packages, but I would use this in Starlette (FastAPI dependency) as soon as it becomes available.

Use case is described on python/typing#1457.

FYI: I'm not trying to reopen this, I'm just randomly commenting.

UltimateLobster · 2023-09-25T06:46:20Z

Just to set expectations, I don't know whether I'd be willing to sponsor the PEP if I had fewer open PEPs; I'd have to think more about whether I think this is a good direction to go into. I'd also prefer to see more evidence of the feasibility of the idea (e.g., buy-in from type checker maintainers, ideally a prototype implementation).

I know you didn't mean for other packages, but I would use this in Starlette (FastAPI dependency) as soon as it becomes available.

Use case is described on python/typing#1457.

FYI: I'm not trying to reopen this, I'm just randomly commenting.

Thank you for the reply!
I am working on a prototype PR right now as well as checking the opinion of different type checker maintainers

Badg · 2024-04-23T11:43:10Z

FWIW, this would allow correct typing of dataclasses.replace (and similar operations, which can be crucial when defining APIs that operate over frozen dataclasses) without any special-casing in type checking, see here

hugovk · 2024-04-23T11:52:09Z

Please direct all discussion to the Discourse thread, thanks!

https://discuss.python.org/t/annotations-using-inner-field-names-and-values-of-typeddicts-dataclass-like-objects/26527

UltimateLobster added 2 commits September 1, 2023 14:28

Added draft for pep728

1d6b98c

Updated discussion link to the relevent one for this pep

a483edb

UltimateLobster requested a review from a team as a code owner September 1, 2023 11:39

AA-Turner changed the title ~~PEP-728 - Initial draft~~ PEP 728: Inner Fields Annotations Sep 1, 2023

AA-Turner reviewed Sep 1, 2023

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AA-Turner added the new-pep A new draft PEP submitted for initial review label Sep 1, 2023

AA-Turner reviewed Sep 1, 2023

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Jackenmen reviewed Sep 2, 2023

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AA-Turner closed this Sep 2, 2023

hugovk changed the title ~~PEP 728: Inner Fields Annotations~~ PEP xxx: Inner Fields Annotations Sep 25, 2023

Badg mentioned this pull request Apr 23, 2024

dataclasses.replace does not type correctly microsoft/pyright#1047

Closed


		The latter problem can be solved using ``typing.overload``:

		.. code-block:: py

		Should __annotations__ be used as the reference table for fields?
		''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

-Naming
-''''''
+Naming
+''''''

	This document is placed in the public domain or under the CC0-1.0-Universal license, whichever is more permissive.
	This document is placed in the public domain or under the
	CC0-1.0-Universal license, whichever is more permissive.

	names and types objects with static layout such as dataclasses (or dataclass-like objects), TypedDicts and NamedTuples.
	names and types objects with static layout such as dataclasses (or dataclass-like objects), :py:class:`~typing.TypedDict`s and :py:class:`~typing.NamedTuple`s.

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PEP xxx: Inner Fields Annotations #3326

PEP xxx: Inner Fields Annotations #3326

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UltimateLobster commented Sep 1, 2023 • edited by AA-Turner Loading Uh oh! There was an error while loading. Please reload this page.

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AA-Turner commented Sep 1, 2023

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AA-Turner commented Sep 2, 2023

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Kludex commented Sep 6, 2023

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UltimateLobster commented Sep 25, 2023

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Badg commented Apr 23, 2024

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hugovk commented Apr 23, 2024

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UltimateLobster commented Sep 1, 2023 •

edited by AA-Turner

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