Provide option to install only dev dependencies

[paveldedik]

Hi,

Thank you for creating this amazing tool! We are in the process of switching from pip-tools to uv and have encountered a situation we’re unsure how to resolve.

Use Case

We have a Python project with the following setup:

1. We install dependencies (excluding dev dependencies) in Docker.

2. We use Docker Compose to mount the site-packages directory to the host machine.

3. On the host machine, we create a virtual environment (venv).

4. Dev dependencies are installed only in this virtual environment.

5. We link the production dependencies (mounted via Docker) to the venv using the following script:

   source .venv/bin/activate
   VENV_SITE_PACKAGES=$(python -c "import site; print(site.getsitepackages()[0])")
   echo "$(realpath var/site-packages/)" > "$VENV_SITE_PACKAGES/core.pth"
   echo "$(realpath app/libs/)" > "$VENV_SITE_PACKAGES/libs.pth"

This setup works well with pip and pip-compile, allowing us to maintain a development environment close to production, with full IDE compatibility.

Challenge with uv

We’d like to transition to pyproject.toml + uv.lock for dependency management.

Steps 1-3 remain the same when using uv. However, we encounter difficulties with step 4, where we need to install only dev dependencies into the virtual environment.

The issue is that:

• uv sync installs both production and dev dependencies.
• uv pip install doesn't respect the pinned dependencies from the lock file.

We’ve considered using the following workaround:

• uv export --format requirements-txt followed by uv pip install <exported-requirements>, but there doesn’t seem to be an option to export only dev dependencies as well (this could be resolved somehow by combination of uv export ... - uv export --no-dev ... outputs, but that is very far from a neat solution.

Conclusion

There may be a better way to handle this setup with uv where project dependencies are mounted over Docker (feel free to suggest them), but at the moment we are missing a way to install only dev dependencies without affecting the linked site-packages.

The obvious solution is to add an option something like uv sync --only-dev + also uv export --only-dev ....

Any guidance or suggestions would be greatly appreciated!

[charliermarsh]

Agree, I do want to support this.