Switching Pip to Uv in a Dockerized Flask / Django App

  # Ensure we always have an up to date lock file.
  if ! test -f uv.lock || ! uv lock --check 2>/dev/null; then
    uv lock
  fi

Doesn't this defeat the purpose of having a lock file? If it doesn't exist or if it's invalid something catastrophic happened to the lock file and it should be handled by someone familiar with the project. Otherwise, why have a lock file at all? The CI will silently replace the lock file and cause potential confusion.

What are the possible remediation steps, however? If there is no lock file at all, this is likely the first run, or it will be overwritten from a git upstream later on anyway; if it's broken, chances are high someone messed up a package installation and creating a fresh lock file seems like the only sensible thing to do.

I also feel like this handles rare edge cases, but it seems like a pretty straightforward way to do so.

If there's no lock file at all, you haven't locked your dependencies, and you should just install whatever is current (don't create a lockfile). If it's broken, you have problems, and you need to abort the deploy.

There is never a reason for an automated system to create a lockfile.

The reason is simple: it allows you to do the install using "sync" in all cases, whether the lockfile exists or not.

Where the lockfile doesn't exist, it creates it from whatever current is, and the lockfile then gets thrown away later. So it's equivalent to what you're saying, it just avoids having two completely separate install paths. I think it's the correct approach.