--no-build-isolation isn't supported for uv tool

[charliermarsh]

I think the use of OnlySystem for Python discovery means that users can't provide a pre-populated environment for (e.g.) PyTorch.

See, e.g., #1715 (comment).

[charliermarsh]

Marking as a bug since I assumed it did work.

[zanieb]

Hm this is tough, it seems really weird to detect a virtual environment when installing a tool?

[charliermarsh]

Note that this is just the environment used for building. It doesn't need to have access to the virtualenv after the build step.

[zanieb]

I guess we can change interpreter lookup when --no-build-isolation is passed, a little weird but better than always doing it.

[charliermarsh]

This might be tricky, we always create a virtualenv for the tool and install into the virtualenv. We'd need to find a way to... give that environment access to the user-provided virtualenv, I think? Like via sitecustomize.py maybe.