`environments` setting ignored in uv.toml?

[dpprdan]

Summary

It seems that environments setting in uv.toml is ignored when writing uv.lock.

MWE:
In an empty directory in a linux environment execute:

cat << EOF > uv.toml
environments = ["sys_platform == 'linux'"]
EOF

uv init
uv add ruff

grep win uv.lock

Output:

Initialized project `test-uv`
Using CPython 3.13.1
Creating virtual environment at: .venv
Resolved 2 packages in 73ms
Installed 1 package in 86ms
 + ruff==0.12.5
    { url = "https://files.pythonhosted.org/packages/3e/b9/053d6445dc7544fb6594785056d8ece61daae7214859ada4a152ad56b6e0/ruff-0.12.5-py3-none-win32.whl", hash = "sha256:dfeb2627c459b0b78ca2bbdc38dd11cc9a0a88bf91db982058b26ce41714ffa9", size = 11751575, upload-time = "2025-07-24T13:26:30.835Z" },
    { url = "https://files.pythonhosted.org/packages/bc/0f/ab16e8259493137598b9149734fec2e06fdeda9837e6f634f5c4e35916da/ruff-0.12.5-py3-none-win_amd64.whl", hash = "sha256:ae0d90cf5f49466c954991b9d8b953bd093c32c27608e409ae3564c63c5306a5", size = 12882273, upload-time = "2025-07-24T13:26:32.929Z" },
    { url = "https://files.pythonhosted.org/packages/00/db/c376b0661c24cf770cb8815268190668ec1330eba8374a126ceef8c72d55/ruff-0.12.5-py3-none-win_arm64.whl", hash = "sha256:48cdbfc633de2c5c37d9f090ba3b352d1576b0015bfc3bc98eaf230275b7e805", size = 11951564, upload-time = "2025-07-24T13:26:34.994Z" },

Compare to adding the same environments setting to pyproject.toml

cat << EOF >> pyproject.toml
[tool.uv]
environments = ["sys_platform == 'linux'"]
EOF

uv sync

grep win uv.lock

Output:

warning: Found both a `uv.toml` file and a `[tool.uv]` section in an adjacent `pyproject.toml`. The following fields from `[tool.uv]` will be ignored in favor of the `uv.toml` file:
- environments
Resolved 2 packages in 177ms
Audited 1 package in 0.59ms

I.e. there aren't any dependencies for Windows present in uv.lock, anymore.

The warning is also not entirely correct in this case, as uv apparently uses the setting in pyproject.toml.
The same warning is shown, when the environments setting is only present in pyproject.toml, so it cannot really be ignored in favor of the uv.toml file, obviously.

Is this a bug or a mistake on my part?

Platform

Ubuntu 24.04.2 x86_64 (WSL)

Version

uv 0.8.3

Python version

Python 3.13.1

[zanieb]

Settings that affect project metadata aren't allowed in the uv.toml.

Sorry the warning is confusing. I thought we fixed this in #14325

[charliermarsh]

It looks like the warning might just be inverted. I believe we respect the pyproject.toml, yeah.

The same warning is shown, when the environments setting is only present in pyproject.toml, so it cannot really be ignored in favor of the uv.toml file, obviously.

I think it's very likely that you still had a uv.toml file around if you're still seeing this.

[charliermarsh]

Yeah, I can't reproduce this if I remove the uv.toml. Maybe you removed your uv.lock by accident instead?

[zanieb]

The warning seems inverted, yeah.

[zanieb]

It's weird we warn here though, we should just error when uv.toml contains environments?

[zanieb]

Which I thought was in #14322

[charliermarsh]

I don't see environments in #14322.

[dpprdan]

Uhm, then let me vote for allowing environments in uv.toml, if I may.

Settings that affect project metadata aren't allowed in the uv.toml.

There's probably a very good reason for that, but IMHO the line between project metadata and config settings is bit blurry. E.g. (maybe not the best example) you might want to set different link-modes per environment. Or if you're developing in some container based setup where you don't really have "machine" configs. Here I'd like to copy just the uv.toml with my settings (including environments) and then just manage the pyproject.toml with uv init, uv add etc.

[dpprdan]

I think it's very likely that you still had a uv.toml file around if you're still seeing this.

Yeah, I can't reproduce this if I remove the uv.toml. Maybe you removed your uv.lock by accident instead?

As hinted at in the post above, I do have other settings in uv.toml, so that is and will be present still.

[dpprdan]

It's weird we warn here though, we should just error when uv.toml contains environments?

Thinking about this a little further, I wonder: Setting e.g. environments = ["sys_platform == 'linux'"] at the user or system level might be a little odd, but is it that bad as to prohibit it altogether?

And then there's the case where uv.toml is in the project directory. It's not really clear to me, why some settings would be mandatory to be set in pyproject.toml whereas others could be in both, I guess?

[dpprdan]

It looks like the warning might just be inverted.

The warning does make sense from the "uv.toml files take precedence over pyproject.toml files" point of view though.

[zanieb]

Setting e.g. environments = ["sys_platform == 'linux'"] at the user or system level might be a little odd, but is it that bad as to prohibit it altogether?

In our current model, we prohibit other settings like this so we'd need to reconsider the model more broadly to allow it.

It's not really clear to me, why some settings would be mandatory to be set in pyproject.toml whereas others could be in both, I guess?

It's... complicated. It seems a little weird to special-case uv.toml files that are in project directories though?