opam is proposing a breaking change solution?

[qexat]

(opening a discussion instead of an issue in case this is a misunderstanding of my part)

opam is proposing to downgrade ansifmt to upgrade re, but that's clearly a breaking change. ansifmt 0.3.0 is definitely not compatible with 2.0.0 and downgrading would break every single project that depends on it.

→ opam update && opam upgrade

<><> Updating package repositories ><><><><><><><><><><><><><><><><><><><><><><>
[default] synchronised from https://opam.ocaml.org
Now run 'opam upgrade' to apply any package updates.
The following actions will be performed:
=== downgrade 1 package
  ↘ ansifmt          2.0.0 to 0.3.0
=== recompile 4 packages
  ↻ ocaml-lsp-server 1.26.0           [uses re]
  ↻ ocamlformat      0.29.0           [uses re]
  ↻ odoc             3.2.1            [uses tyxml]
  ↻ tyxml            4.6.0            [uses re]
=== upgrade 1 package
  ↗ re               1.12.0 to 1.14.0

why is it doing that? is this a bug in the opam default solver, somewhere else, or did I miss something?

[kit-ty-kate]

downgrading would break every single project that depends on it.

Are any of these projects installed? If not, then opam can't know downgrading this package would break them.
If you're talking about local packages whose dependencies were installed with --deps-only but the packages are not installed themselves then this would require a rather large change to how opam works currently (see #6588). Hopefully we can fix that in the future but currently it's a bit tricky, if that's indeed your case sorry about that.

In the meantime pinning ansifmt using opam pin add ansifmt 2.0.0 should fix your issue, but it's not ideal.