Add a --output and -o flag to uv export

[SamEdwardes]

Background

Thank you for adding the uv export command. It is a great feature. One improvement that would be helpful is to include an option to export the data to a file. For example, currently you can do this:

uv export > requirements.txt

However, it would be a nice feature to have an output flag. For example:

uv export --output requirements.txt
# or...
uv export -o requirements.txt

This is the same approach that poetry uses: https://python-poetry.org/docs/cli/#export

Why

Using > or >> requires the user to have more advanced shell knowledge. Having an output flag could be easier for users.

System

❯ uv --version
uv 0.4.5 (42b6bfbad 2024-09-04)

[zanieb]

We can also do an atomic write with this.

[zanieb]

Also needed for astral-sh/uv-pre-commit#16

[charliermarsh]

Why is it needed there vs. piping the output? Just curious.

[zanieb]

I think so users can customize the file name via args:? (mostly echoing the chat there)

[SamEdwardes]

Why is it needed there vs. piping the output? Just curious.

It is definitely not needed. But I think it is a nice to have:

• Less experience shell users may not be familiar with piping.
• More consistent API across uv (e.g. uv pip compile requirements.in --output-file requirements.txt)
  • So maybe using --output-file is the best choice to be consistent
• More consistent with other tools:
  • Poetry: poetry export --output (https://python-poetry.org/docs/cli/#export)
  • Pip tools: pip-compile --all-build-deps --all-extras --output-file=constraints.txt (https://github.com/jazzband/pip-tools)
• On the other hand... I did some research and some other tools have no export option:
  • conda: https://stackoverflow.com/a/57845418/11349897
  • pipenv: pipenv requirements > requirements.txt (https://pipenv.pypa.io/en/latest/advanced.html#generating-a-requirements-txt)

[charliermarsh]

I will do this quickly.

[SamEdwardes]

Awesome thank you Charlie!

[FishAlchemist]

Why is it needed there vs. piping the output? Just curious.

I think this feature is necessary, mainly due to text encoding issues. UV writes files would allow us to unify text encoding. If we use piped output, the encoding would depend on the settings or defaults, just like how PowerShell has different encoding behaviors.

https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_character_encoding?view=powershell-7.4