Add `constraints.txt` export to `uv export`

[charliermarsh]

Constraints files are a little different... Specifically, every requirement has to be named, so we can't write relative paths. (You also can't include extras, but we already don't do that.)

[zanieb]

Hm. An export of the pyproject.toml constraints?

[charliermarsh]

No, it’s an export of the lockfile in constraints.txt format. requirements.txt files support things that constraints files do not. You can’t export in requirements.txt format and pass it as constraints.

[carderne]

I've had this line in every rye-based Dockerfile for the last few years to work around this.

RUN sed -i '/^-e ./d' requirements.txt

[charliermarsh]

@carderne -- If you structure your project as a non-package (i.e., omit a [build-system] or set package = false under [tool.uv]), that line should be omitted from the export.

[carderne]

Sorry maybe I crossed a wire. To be super explicit, this works:

uv init --package foo
cd foo
uv sync
uv run python -c 'import foo'

But if I set tool.uv.package = false then I obviously can't import foo.

I want foo to be installed in the venv, but I don't want it in the constraints file, as pip rejects that.

(Happy to have a thumbs up and go on my way, I might be derailing the point of this thread.)