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.

Hi author here.

If you end up with an invalid lock file, it doesn't silently fail and move on with a generated lock file. The `uv lock` command fails with a helpful message and then errexit from the shell script kicks in.

The reason I redirected the uv lock --check command's errors to /dev/null is because `uv lock` throws the same error and I wanted to avoid outputting it twice.

For example, I made my lock file invalid by manually switching one of the dependencies to a version that doesn't match the expected SHA.

Then I ran the same script you partially quoted and it yields this error which blocks the build and gives a meaningful message that a human can react to:

    1.712 Using CPython 3.13.3 interpreter at: /usr/local/bin/python3
    1.716 error: Failed to parse `uv.lock`
    1.716   Caused by: The entry for package `amqp` v5.3.4 has wheel `amqp-5.3.1-py3-none-any.whl` with inconsistent version: v5.3.1
    ------
    failed to solve: process "/bin/sh -c chmod 0755 bin/* && bin/uv-install" did not complete successfully: exit code: 2

This error is produced from `uv lock` when the if condition evaluates to true.

With that said, this logic would be much clearer which I just commit and pushed:

    if test -f uv.lock; then
      uv lock --check
    else
      uv lock
    fi

As for a missing lock file, yep it will generate one but we want that. The expectation there is we have nothing to base things off of, so let's generate a fresh one and use it moving forward. The human expectation in a majority of the cases is to generate one in this spot and then you can commit it so moving forward one exists.