Allow `uv venv` to throw error instead of prompting

[notatallshaw]

Summary

I often use imperative commands as part of a script, e.g. uv pip, uv venv.

I therefore want them to fail with a non-zero status code when they can't complete an action.

But it appears uv venv only has two options when the directory it's writing to is non-empty:

• Automatically delete everything in the directory,
• Prompt for user interaction.

But I want uv venv to fail without user prompt, is that currently possible? I don't see an option.

Example

cd /
uv venv .

[zanieb]

uv venv should fail without a tty instead of prompting, are you seeing otherwise?

[zanieb]

Anyway, the fix is to add --no-clear which will always error if it needs to clear.

[notatallshaw]

uv venv should fail without a tty instead of prompting, are you seeing otherwise?

Don't think that's relevant to my use case of running a bash script locally?

Create test_tty.sh:

if tty -s; then
  echo "Has a TTY"
else
  echo "No TTY"
fi

Then:

$ bash test_tty.sh 
Has a TTY

As a side note, as someone who has wrote far too many shell scripts, I don't love commands behaving differently based on environment output capabilities, at most I would only want the output to change, and even then I would always want an option to make it the same regardless of environment.

This kind of magic, where a command tries to preempt the user and "do the right thing", can cause a lot of pain to script users.

[zanieb]

The alternative was going straight to a hard-failure, which we didn't want to do since it's a disruptive breaking change.

[notatallshaw]

The alternative was going straight to a hard-failure, which we didn't want to do since it's a disruptive breaking change.

I personally would have preferred this, it's consistent and logical, though I understand the compromise it has made uv venv magical in a way that other imperative commands aren't.

And it's incorrectly documented:

uv venv docs still document old behavior:

If a virtual environment exists at the target path, it will be removed and a new, empty virtual environment will be created.

And clear flag docs actually state uv venv will exit with an error, nothing about the user prompt:

Remove any existing files or directories at the target path.

By default, uv venv will exit with an error if the given path is non-empty. The --clear option will instead clear a non-empty path before creating a new virtual environment.

May also be set with the UV_VENV_CLEAR environment variable.

[harshithvh]

@notatallshaw is this fixed?

[notatallshaw]

@harshithvh No

[zanieb]

Closed by #15795