[opam-devel] Determining all required versions of all packages

[Louis Gesbert]

Le mardi 10 novembre 2015, 09:12:08 David Allsopp a écrit :
> I'm starting to assemble high quality Windows amendments[1] for
> opam-repository in dra27/opam-repository/opam-windows. OPAM's age and the
> speed at which OCaml development moves means lots of packages have many
> versions (see, for example,
> https://github.com/dra27/opam-repository/commit/b7269d2ac853aeb45b1096ec0dba
> 7febbad149f2).
> 
> Patching them all is tedious (and actually testing the installation of each
> version even more so!), especially as it's not that likely that too many
> people will ever bother installing older versions. Is there already a clever
> way where given a repository I can query all dependent packages of a
> specific version of each package. Most (probably all) packages depend just
> on ocamlfind, for example, not on ocamlfind 1.4.x?

It's not repository-specific, but

    opam list --rec --depends-on <pkglist>

will give you the packages depending on the mentionned packages. Now it seems 
that what you want to know is all packages that _would be made uninstallable_ 
if you were to remove this package. The closest we have to that is implemented 
within the camelus bot, but submitting a PR with the given package removed is 
likely not the UI you were hoping for :)

That part of the code is quite simple though [1], you build two package 
universes using sets of opam files, call `OpamSolver.installable` on them, then 
do some set operations. This completely ignores compiler/os constraints 
though, so for something more thorough you may want to look into the more 
complete Dose lib, like OWS does.

The script here [2] also tries to cover all installable packages in a minimum 
of steps (greedily, minimum is not guaranteed at all). So another approach may 
be to just run that and take the union of all solutions it returns.

Best,
Louis Gesbert - OCamlPro


[1]: https://github.com/AltGr/opam-bot/blob/aaa4ddefc83f9906480d24ae52d6da5c2a567ceb/opam_ci.ml#L320-L377

[2]: https://github.com/ocaml/opam/blob/master/admin-scripts/couverture.ml