Consider setting a fixed minimum Rust version about pydantic-core

[arnaudsjs]

I think this change in the rust compiler introduced in v1.74.0 (See also: RFC) is causing the issue.

[locobastos]

Hello, same issue with:

• python 3.11.5
• rustc 1.71.1 (eb26296b5 2023-08-03) (Red Hat 1.71.1-1.module_el8.9.0+3639+04ae6405)
• pydantic-core 2.16.2

EDIT1: I'm looking for the most recent version that is compatible with rust 1.71.1 on AlmaLinux 8 and I will give the result here
EDIT2: I've not seen that I've the same environment than @arnaudsjs
EDIT3: pydantic-core 2.15.0 is building with our environment. But I've not found any pydantic version that requires this exact version.

From what I've found, at the moment, Pydantic 2.5.3 + Pydantic-Core 2.14.6 are the latest versions working with Rust 1.71.1.

[PatrickBaus]

This issue also persists with alpine Linux <= 3.19 as it uses Rust 1.72.1-r0. This breaks my builds of a python docker container for the ARMv6 Raspberry Pi platform.

As said above, the last working version is Pydantic 2.5.3 + Pydantic-Core 2.14.6.

• Python 3.11.6-r1
• Rust 1.72.1-r0

[locobastos]

Red Hat is pretty slow to release packages because of their aim of the stability. Anyway, here is what I've found on the version history:

• Rust 1.47.0
  --> Released on 8 October 2020
  --> Available in AlmaLinux 8.3 repository on 12 March 2021
  --> + 155 days
• Rust 1.49.0
  --> Release on 31 December 2020
  --> Available in AlmaLinux 8.4 repository on 17 April 2021
  --> + 107 days
• Rust 1.52.1
  --> Released on 10 May 2021
  --> Available in AlmaLinux 8.4 repository on 11 August 2021
  --> + 101 days
• Rust 1.54.0
  --> Released on 29 July 2021
  --> Available in AlmaLinux 8.5 repository on 10 October 2021
  --> + 73 days
• Rust 1.58.1
  --> Released on 20 January 2022
  --> Available in AlmaLinux 8.6 repository on 12 April 2022
  --> + 82 days
• Rust 1.62.1
  --> Released on 19 July 2022
  --> Available in AlmaLinux 8.7 repository on 13 October 2022
  --> + 86 days
• Rust 1.66.1
  --> Released on 10 January 2023
  --> Available in AlmaLinux 8.8 repository on 6 April 2023
  --> + 86 days
• Rust 1.71.1
  --> Released on 3 August 2023
  --> Available 18 October 2023
  --> + 49 days

It seems they decrease the time between the release date and the availibility date, but I also know that they will release only versions they need.

[arnaudsjs]

@davidhewitt I won't have the time to work on this. We are currently working around this issue by using the binary wheel instead. We were facing this issue on RockyLinux 8, which is like AlmaLinux, a binary-compatible derivative of RedHat Enterprise Linux. So the above-mentioned table should hold for both AlmaLinux, RockyLinux and RedHat Enterprise Linux.

[davidhewitt]

@arnaudsjs are you able to try building with latest Rust stable? (Rust 1.75.0 at present.)

[arnaudsjs]

I tried building the package with Rust version 1.75.0 and like that the build does work.

[samuelcolvin]

What's the reason you need to build with older rust?

[locobastos]

Because neither AlmaLinux 8 nor AlmaLinux 9 has a newer version of Rust available in the official repositories.

[davidhewitt]

I think we should add an official minimum supported rust-version to our Cargo.toml and also test it in CI. Based on the features that we heavily use in this repository, I suspect that we could make something in the range 1.65 - 1.71 work, with a little effort.

It would likely not be a breaking change so we should be able to ship this as a patch release.

@arnaudsjs @locobastos would either of you be interested in helping create a PR to extend our rust support backwards and guarantee it?

Also, do you know how frequently AlmaLinux updates available Rust version? It would be helpful to know how many versions we should consider lagging current stable by.

[locobastos]

@samuelcolvin,

It's not a big deal, it just means that building on RHEL8-like distro is limited to an older version of pydantic + pydantic-core.
We can have newer version by using pip3 install pydantic pydantic-core:

Successfully installed annotated-types-0.6.0 pydantic-2.6.1 pydantic-core-2.16.2 typing-extensions-4.9.0

[locobastos]

@davidhewitt, I will not have the time to help you. The only one thing I will do, is to try on an AlmaLinux 8 docker container as I'm doing today. I'm not sure I'll have a capital gains on this issue. @arnaudsjs already gave the command to reproduce this issue.

[davidhewitt]

Thanks @locobastos, that table is very helpful 👍

[BtbN]

This is also happening on Alpine, for which no wheels are available.
The latest rust version available there is 1.72, and installing a lot of stuff has recently become impossible, specially if pydantic-core is a build-time dependency.

[davidhewitt]

@BtbN I'm surprised you are finding there are no Alpine wheels, we do build for musllinux.

Can you run pip debug and show the first 10 compatible tags it lists? E.g. for my desktop I get

Compatible tags: 1041
  cp312-cp312-manylinux_2_38_x86_64
  cp312-cp312-manylinux_2_37_x86_64
  cp312-cp312-manylinux_2_36_x86_64
  cp312-cp312-manylinux_2_35_x86_64
  cp312-cp312-manylinux_2_34_x86_64
  cp312-cp312-manylinux_2_33_x86_64
  cp312-cp312-manylinux_2_32_x86_64
  cp312-cp312-manylinux_2_31_x86_64
  cp312-cp312-manylinux_2_30_x86_64
  cp312-cp312-manylinux_2_29_x86_64
  ...
  [First 10 tags shown. Pass --verbose to show all.]

[davidhewitt]

We have a user needing 1.68 in #1202.

To extend back that far we'd need to replace our OnceLock from the std library with the external once_cell crate. Not the end of the world.

[hsteinhaus]

Thanks @davidhewitt for pointing me to this issue.

Is there a chance to catch that type of problem earlier, i.e. with some kind of an explicit dependency check before failing with an obscure compile error?

[davidhewitt]

Yes, there is a rust-version key we should set in the Cargo.toml. #1206 will do that.