--resolution lowest with uv sync needs to discard preferences

[konstin]

Currently, when switching to uv sync --resolution lowest from uv sync, nothing changes, because we're using the existing preferences. This breaks the use case for --resolution lowest.

We should instead discard the preferences when using --resolution lowest or --resolution lowest-direct, since these two modes are not for regular development, but for testing your dependency specifiers.

[charliermarsh]

I don't consider this a bug, but we can consider changing it.

[charliermarsh]

I don't think discarding preferences alone would change this. We'd also have to skip the "resolve from lockfile" behavior.

[charliermarsh]

Perhaps we always do both these things if --resolution is set explicitly...? Like, say that it implies --upgrade?

[charliermarsh]

I can try it.

[charliermarsh]

I guess arguably --prerelease and other settings should have the same effect, but I don't know where to draw the line.

[konstin]

Do we need to record the settings used for the resolution in uv.lock?

[charliermarsh]

The downside of that approach is that it wouldn't work for uv pip install --resolution lowest, which has also led to confusion before and would be nice to solve here.

[charliermarsh]

No obviously-good solution here... Options are something like:

• Use --upgrade semantics whenever --resolution is explicitly provided. But, how does this work when --resolution is provided via a configuration file? We never pin? That wouldn't work.
• Write the resolution and prerelease to the lockfile, so that we can rerun when they're mismatched. This is good, but it doesn't solve the same problem that already exists for uv pip install, which has been described before: I expected --resolution=lowest to imply --reinstall for an existing package #1647.

I suspect we need to do the latter, though.

[charliermarsh]

We probably want to record the resolution, prerelease, and exclude-newer setting.

[charliermarsh]

Working on that change (adding resolution options to the lockfile).

[charliermarsh]

I wonder if, eventually, we'd want to enable projects to have multiple locks for this purpose. Or enable the lockfile to contain multiple entries if they resolve with different input settings.

[zanieb]

It seems like it depends on the use-case. Are you going to always run your project in lowest resolution because you prefer it? I don't know why you'd need multiple lock files in that case. Or is it a single invocation in CI to test if the lowest versions are correct? There, I don't think the lock matters at all?

[charliermarsh]

Are you commenting on the originating issue here or my previous comment?

[zanieb]

The previous comment.