Update To Pydantic Version 2
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.
Summary
python-pydantic
Owner
- Name: Maxwell G; Benjamin Beasley; Python SIG
- Email: maxwell@gtmx.me; code@musicinmybrain.net; python-devel@lists.fedoraproject.org
Current status
- Targeted release: Fedora Linux 40
- Last updated: 2023-10-03
- [<will be assigned by the Wrangler> devel thread]
- [<will be assigned by the Wrangler> Discussions thread]
- FESCo issue: <will be assigned by the Wrangler>
- Tracker bug: <will be assigned by the Wrangler>
- Release notes tracker: <will be assigned by the Wrangler>
Detailed Description
Pydantic is a Python data validation library.
Recently, upstream released a new major version with many fixes and performance
improvements but also some breaking API changes.
The new release relies on
We will update pydantic to version 2 after making sure dependent packages are accounted for.
Porting strategies
Pydantic v2 contains some breaking API changes that may require porting if packages depend on old functionality. Upstream provides a detailed Migration Guide that describes the breaking API changes.
Projects that are not ready to port to pydantic v2 may use the pydantic.v1
compatibility module which contains a full copy of the old pydantic v1 code.
https://github.com/matrix-org/synapse/pull/16332 exemplifies this approach.
As shown in the above PR, projects can use conditional imports to import
pydantic.v1 if pydantic v2 is in use and otherwise fall back to importing
pydantic if pydantic v1 is in use.
Maintaining compatibility for both pydantic v1 and v2 in the same codebase
without the compatibility module is possible but may not be practical for
larger, more complex usecases.
fedrq uses this approach
and silences pydantic.PydanticDeprecatedSince20 warnings.
Many of these deprecation warnings cannot be resolved without dropping support
for pydantic v1.
Feedback
I did not receive much feedback as of yet, but I expect this change to be uncontroversial.
Benefit to Fedora
Fedora will have the latest version of pydantic in its repositories. The new version touts a significant performance boost, amongst other improvements.
Scope
- Proposal owners:
- Preform an impact check
- Make an inventory of failures or packages that have a hard dependency on pydantic v1.
- Submit distgit PRs and/or file upstream issues to fix incompatibilities in dependent packages
- Submit new python-pydantic-settings and python-pydantic-extra-types packages for review
- Wait two weeks for packagers to review PRs. Those that remain compatible with pydantic v1 can be merged immediately.
- Build pydantic v2 package and any outstanding PRs in a side tag.
- Other developers:
- Test your package to ensure it still builds and functions with pydantic v2
- Help with package reviews
Upgrade/compatibility impact
Pydantic version 2 has some breaking API changes. See upstream's Migration Guide.
How To Test
You can preform test builds like this:
$ copr mock-config gotmax23/pydanticv2-testing fedora-rawhide-x86_64 > ~/.config/pydanticv2.cfg $ fedpkg --release=rawhide mockbuild --root pydanticv2
User Experience
This isn't a particularly user visible change. Users of Python applications that utilize Pydantic should notice a performance improvement.
Dependencies
See https://gtmx.me/Wiki/Fedora/pydantic-v2-update/#lists for a list of dependent packages. The Change owners will work with these packages' maintainers to ensure the packages remain functional with the new pydantic version.
Contingency Plan
- Contingency mechanism: N/A (not a System Wide Change)
- Contingency deadline: N/A (not a System Wide Change)
- Blocks release? N/A (not a System Wide Change)
Documentation
See https://gtmx.me/Wiki/Fedora/pydantic-v2-update/ for the current status and notes.
Release Notes
python3-pydantic was updated from 1.10.x to 2.x.0. Pydantic v2 brings performance improvements and an API refactoring, amongst other changes. See upstream's Migration Guide for a full inventory of breaking changes.