Use positional-only `self` in `BaseModel` constructor, so no field name can ever conflict with it. #8072

ariebovenberg · 2023-11-09T21:58:29Z

Change Summary

As discussed in #7948, there is an edge case in the BaseModel constructor where using __pydantic_self__ would give a TypeError instead of an expected ValidationError. This edge case can be solved by using positional-only arguments — as soon as Python 3.7 support is dropped (see #7188)

Related issue number

Fixes #7948

Checklist

The pull request title is a good summary of the changes - it will be used in the changelog
Unit tests for the changes exist
Tests pass on CI
Documentation reflects the changes where applicable
My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

Notes

I didn't make the changes for the v1 module. I assume you'd rather not make any changes to it, right?
CI for Python 3.7 will fail until support is officially dropped. Then, I'll rebase the changes and it'll be ready for review.

Selected Reviewer: @lig

tests/test_edge_cases.py

sydney-runkle · 2023-11-13T18:33:28Z

@ariebovenberg,

I'm hoping to get the PR dropping Python 3.7 support across the line tomorrow, then we can move forward with this :). Thanks!

codspeed-hq · 2023-11-14T18:28:15Z

CodSpeed Performance Report

Merging #8072 will not alter performance

_{Comparing ariebovenberg:basemodel-self (4b3110a) with main (eb90b59)}

Summary

✅ 10 untouched benchmarks

ariebovenberg · 2023-11-14T19:41:40Z

@PrettyWood: it should be ready for review now, although I don't know what the one "release notes" check is about 🤔

There was an interesting wrinkle with the mypy plugin, which interestingly doesn't support positional-only arguments internally. I've added a comment explaining the workaround.

ariebovenberg · 2023-11-14T19:42:15Z

Forgot the exact phrase, so here it is: please review

tests/test_edge_cases.py

sydney-runkle

@ariebovenberg,

Looks fantastic. Thanks for adding the simple test and the additional mypy docs.

Thanks @PrettyWood for the review as well :)

sydney-runkle · 2023-11-17T18:43:32Z

pydantic/mypy.py

+        # `self` is positional *ONLY* here, but this can't be expressed
+        # fully in the mypy internal API. ARG_POS is the closest we can get.
+        # Using ARG_POS will, however, give mypy errors if a `self` field
+        # is present on a model:
+        #
+        #     Name "self" already defined (possibly by an import)  [no-redef]
+        #
+        # As a workaround, we give this argument a name that will
+        # never conflict. By its positional nature, this name will not
+        # be used or exposed to users.


Thanks for adding this explanation 👍

This PR contains the following updates: | Package | Type | Update | Change | |---|---|---|---| | [pydantic](https://github.com/pydantic/pydantic) ([changelog](https://docs.pydantic.dev/latest/changelog/)) | dependencies | minor | `2.5.3` -> `2.6.1` | --- ### Release Notes <details> <summary>pydantic/pydantic (pydantic)</summary> ### [`v2.6.1`](https://github.com/pydantic/pydantic/blob/HEAD/HISTORY.md#v261-2024-02-05) [Compare Source](pydantic/pydantic@v2.6.0...v2.6.1) [GitHub release](https://github.com/pydantic/pydantic/releases/tag/v2.6.1) ##### What's Changed ##### Packaging - Upgrade to `pydantic-core` 2.16.2 by [@sydney-runkle](https://github.com/sydney-runkle) in [#8717](pydantic/pydantic#8717) ##### Fixes - Fix bug with `mypy` plugin and `no_strict_optional = True` by [@dmontagu](https://github.com/dmontagu) in [#8666](pydantic/pydantic#8666) - Fix `ByteSize` error `type` change by [@sydney-runkle](https://github.com/sydney-runkle) in [#8681](pydantic/pydantic#8681) - Fix inheriting `Field` annotations in dataclasses by [@sydney-runkle](https://github.com/sydney-runkle) in [#8679](pydantic/pydantic#8679) - Fix regression in core schema generation for indirect definition references by [@dmontagu](https://github.com/dmontagu) in [#8702](pydantic/pydantic#8702) - Fix unsupported types bug with `PlainValidator` by [@sydney-runkle](https://github.com/sydney-runkle) in [#8710](pydantic/pydantic#8710) - Reverting problematic fix from 2.6 release, fixing schema building bug by [@sydney-runkle](https://github.com/sydney-runkle) in [#8718](pydantic/pydantic#8718) - Fix warning for tuple of wrong size in `Union` by [@davidhewitt](https://github.com/davidhewitt) in [pydantic/pydantic-core#1174](pydantic/pydantic-core#1174) - Fix `computed_field` JSON serializer `exclude_none` behavior by [@sydney-runkle](https://github.com/sydney-runkle) in [pydantic/pydantic-core#1187](pydantic/pydantic-core#1187) ### [`v2.6.0`](https://github.com/pydantic/pydantic/blob/HEAD/HISTORY.md#v260-2024-01-23) [Compare Source](pydantic/pydantic@v2.5.3...v2.6.0) [GitHub release](https://github.com/pydantic/pydantic/releases/tag/v2.6.0) The code released in v2.6.0 is practically identical to that of v2.6.0b1. ##### What's Changed ##### Packaging - Check for `email-validator` version >= 2.0 by [@commonism](https://github.com/commonism) in [#6033](pydantic/pydantic#6033) - Upgrade \`ruff\`\` target version to Python 3.8 by [@Elkiwa](https://github.com/Elkiwa) in [#8341](pydantic/pydantic#8341) - Update to `pydantic-extra-types==2.4.1` by [@yezz123](https://github.com/yezz123) in [#8478](pydantic/pydantic#8478) - Update to `pyright==1.1.345` by [@Viicos](https://github.com/Viicos) in [#8453](pydantic/pydantic#8453) - Update pydantic-core from 2.14.6 to 2.16.1, significant changes from these updates are described below, full changelog [here](pydantic/pydantic-core@v2.14.6...v2.16.1) ##### New Features - Add `NatsDsn` by [@ekeew](https://github.com/ekeew) in [#6874](pydantic/pydantic#6874) - Add `ConfigDict.ser_json_inf_nan` by [@davidhewitt](https://github.com/davidhewitt) in [#8159](pydantic/pydantic#8159) - Add `types.OnErrorOmit` by [@adriangb](https://github.com/adriangb) in [#8222](pydantic/pydantic#8222) - Support `AliasGenerator` usage by [@sydney-runkle](https://github.com/sydney-runkle) in [#8282](pydantic/pydantic#8282) - Add Pydantic People Page to docs by [@sydney-runkle](https://github.com/sydney-runkle) in [#8345](pydantic/pydantic#8345) - Support `yyyy-MM-DD` datetime parsing by [@sydney-runkle](https://github.com/sydney-runkle) in [#8404](pydantic/pydantic#8404) - Added bits conversions to the `ByteSize` class [#8415](pydantic/pydantic#8415) by [@luca-matei](https://github.com/luca-matei) in [#8507](pydantic/pydantic#8507) - Enable json schema creation with type `ByteSize` by [@geospackle](https://github.com/geospackle) in [#8537](pydantic/pydantic#8537) - Add `eval_type_backport` to handle union operator and builtin generic subscripting in older Pythons by [@alexmojaki](https://github.com/alexmojaki) in [#8209](pydantic/pydantic#8209) - Add support for `dataclass` fields `init` by [@dmontagu](https://github.com/dmontagu) in [#8552](pydantic/pydantic#8552) - Implement pickling for `ValidationError` by [@davidhewitt](https://github.com/davidhewitt) in [pydantic/pydantic-core#1119](pydantic/pydantic-core#1119) - Add unified tuple validator that can handle "variadic" tuples via PEP-646 by [@dmontagu](https://github.com/dmontagu) in [pydantic/pydantic-core#865](pydantic/pydantic-core#865) ##### Changes - Drop Python3.7 support by [@hramezani](https://github.com/hramezani) in [#7188](pydantic/pydantic#7188) - Drop Python 3.7, and PyPy 3.7 and 3.8 by [@davidhewitt](https://github.com/davidhewitt) in [pydantic/pydantic-core#1129](pydantic/pydantic-core#1129) - Use positional-only `self` in `BaseModel` constructor, so no field name can ever conflict with it by [@ariebovenberg](https://github.com/ariebovenberg) in [#8072](pydantic/pydantic#8072) - Make `@validate_call` return a function instead of a custom descriptor - fixes binding issue with inheritance and adds `self/cls` argument to validation errors by [@alexmojaki](https://github.com/alexmojaki) in [#8268](pydantic/pydantic#8268) - Exclude `BaseModel` docstring from JSON schema description by [@sydney-runkle](https://github.com/sydney-runkle) in [#8352](pydantic/pydantic#8352) - Introducing `classproperty` decorator for `model_computed_fields` by [@Jocelyn-Gas](https://github.com/Jocelyn-Gas) in [#8437](pydantic/pydantic#8437) - Explicitly raise an error if field names clashes with types by [@Viicos](https://github.com/Viicos) in [#8243](pydantic/pydantic#8243) - Use stricter serializer for unions of simple types by [@alexdrydew](https://github.com/alexdrydew) [pydantic/pydantic-core#1132](pydantic/pydantic-core#1132) ##### Performance - Add Codspeed profiling Actions workflow by [@lambertsbennett](https://github.com/lambertsbennett) in [#8054](pydantic/pydantic#8054) - Improve `int` extraction by [@samuelcolvin](https://github.com/samuelcolvin) in [pydantic/pydantic-core#1155](pydantic/pydantic-core#1155) - Improve performance of recursion guard by [@samuelcolvin](https://github.com/samuelcolvin) in [pydantic/pydantic-core#1156](pydantic/pydantic-core#1156) - `dataclass` serialization speedups by [@samuelcolvin](https://github.com/samuelcolvin) in [pydantic/pydantic-core#1162](pydantic/pydantic-core#1162) - 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Fix bug with schema generation with `Field(...)` in a forward ref by [@dmontagu](https://github.com/dmontagu) in [#8494](pydantic/pydantic#8494) - Fix ordering of keys in `__dict__` with `model_construct` call by [@sydney-runkle](https://github.com/sydney-runkle) in [#8500](pydantic/pydantic#8500) - Fix module `path_type` creation when globals does not contain `__name__` by [@hramezani](https://github.com/hramezani) in [#8470](pydantic/pydantic#8470) - Fix for namespace issue with dataclasses with `from __future__ import annotations` by [@sydney-runkle](https://github.com/sydney-runkle) in [#8513](pydantic/pydantic#8513) - Fix: make function validator types positional-only by [@pmmmwh](https://github.com/pmmmwh) in [#8479](pydantic/pydantic#8479) - Fix usage of `@deprecated` by [@Viicos](https://github.com/Viicos) in [#8294](pydantic/pydantic#8294) - Add more support for private attributes in `model_construct` call by [@sydney-runkle](https://github.com/sydney-runkle) in [#8525](pydantic/pydantic#8525) - 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Tweak ordering of definitions in generated schemas by [@StrawHatDrag0n](https://github.com/StrawHatDrag0n) in [#8583](pydantic/pydantic#8583) ##### New Contributors ##### `pydantic` - [@ekeew](https://github.com/ekeew) made their first contribution in [#6874](pydantic/pydantic#6874) - [@lambertsbennett](https://github.com/lambertsbennett) made their first contribution in [#8054](pydantic/pydantic#8054) - [@vincent-hachin-wmx](https://github.com/vincent-hachin-wmx) made their first contribution in [#8138](pydantic/pydantic#8138) - [@QuentinSoubeyranAqemia](https://github.com/QuentinSoubeyranAqemia) made their first contribution in [#7825](pydantic/pydantic#7825) - [@ariebovenberg](https://github.com/ariebovenberg) made their first contribution in [#8072](pydantic/pydantic#8072) - [@LukeTonin](https://github.com/LukeTonin) made their first contribution in [#8223](pydantic/pydantic#8223) - [@denisart](https://github.com/denisart) made their first contribution in [#8231](pydantic/pydantic#8231) - 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ariebovenberg marked this pull request as ready for review November 14, 2023 19:38

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Replace __pydantic_self__ with positional-only self

4b3110a

sydney-runkle approved these changes Nov 17, 2023

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sydney-runkle merged commit 7f4cfe5 into pydantic:main Nov 17, 2023
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ariebovenberg deleted the basemodel-self branch November 17, 2023 18:47

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Use positional-only `self` in `BaseModel` constructor, so no field name can ever conflict with it. #8072

Use positional-only `self` in `BaseModel` constructor, so no field name can ever conflict with it. #8072

ariebovenberg commented Nov 9, 2023 •

edited

sydney-runkle commented Nov 13, 2023

codspeed-hq bot commented Nov 14, 2023 •

edited

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sydney-runkle Nov 17, 2023

Use positional-only self in BaseModel constructor, so no field name can ever conflict with it. #8072

Use positional-only self in BaseModel constructor, so no field name can ever conflict with it. #8072

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ariebovenberg commented Nov 9, 2023 • edited

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Use positional-only `self` in `BaseModel` constructor, so no field name can ever conflict with it. #8072

Use positional-only `self` in `BaseModel` constructor, so no field name can ever conflict with it. #8072

ariebovenberg commented Nov 9, 2023 •

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edited