opam's solver strange results with version constraints

[smondet]

With the cannonical opam-repo (at 0fbd60c762a81f4f0c53c6fe12f1c3f583fa3d8b), opam 0.9.2, and after a fresh switch to 4.00.1:

core 109.09.00 seems available

$ opam info core
...
  available-versions: 108.00.02, 108.07.00, 108.07.01, 109.07.00, 109.09.00

 $ cat packages/core.109.09.00/opam | grep ocaml-version
ocaml-version: [>= "4.00.1"]

but

 $ opam install core

wants to install 109.08.00.

but forcing seems to work:

 $ opam install core.109.09.00
.... <works> ...
 $ opam list -i | grep core
core           109.09.00  Industrial strength...

but then the solver wants to downgrade:

  $ opam upgrade
The following actions will be performed:
 - recompile base-unix.base [upstream changes]
 - recompile base-bigarray.base [upstream changes]
 - downgrade type_conv.109.09.00 to 109.08.00 [required by core]
 - recompile base-threads.base [upstream changes]
 - downgrade bin_prot.109.09.00 to 109.08.00 [required by core]
 - downgrade comparelib.109.09.00 to 109.08.00 [required by core]
 - downgrade fieldslib.109.09.00 to 109.08.00 [required by core]
 - downgrade pa_ounit.109.09.00 to 109.08.00 [required by core]
 - downgrade pipebang.109.09.00 to 109.08.00 [required by core]
 - downgrade sexplib.109.09.00 to 109.08.00 [required by core]
 - downgrade variantslib.109.09.00 to 109.08.00 [required by core]
 - downgrade core.109.09.00 to 109.08.00
0 to install | 3 to reinstall | 0 to upgrade | 9 to downgrade | 0 to remove
Do you want to continue ? [Y/n] n

or the solver gets lost and timeouts (and this time it wants to downgrade to yet an older version of the core family):

 $ opam install core_extended
....................... brute-force exploration timed-out [11646 states, 5s].
You might need to add explicit version constraints to your request to get a better answer.
The following actions will be performed:
 - install pcre-ocaml.6.2.5 [required by core_extended]
 - downgrade type_conv.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade bin_prot.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade comparelib.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade fieldslib.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade pa_ounit.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade pipebang.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade sexplib.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade variantslib.109.09.00 to 108.07.01 [required by core_extended]
 - downgrade core.109.09.00 to 108.07.01 [required by core_extended]
 - install core_extended.108.07.01
2 to install | 0 to reinstall | 0 to upgrade | 9 to downgrade | 0 to remove
Do you want to continue ? [Y/n] n

PS: This error message can be quite misleading:

 $ opam install core.109.09
Version 109.09 of "core" is incompatible with your compiler or your OS.

[samoht]

HEAD's solver should give much better results. Could you try to see if there are some improvements ?

Also, the error message should also see fixed (see #463).

[smondet]

Is HEAD supposed to work with 0.9.2 ~/.opam/ trees?

 $ opam switch list
'opam switch' failed.
Fatal error: exception File "src/client/opamSwitchCommand.ml", line 30, characters 20-26: Assertion failed

Apart from that, yes the initial issue seems solved.

opam upgrade got all the 109.09.00 packages, and also uninstalling everything, and installing core and core_extended again gets the expected packages

But I had to restart the re-installations because of ocamlfind install errors

First time:

$ opam install core
...
### stderr ###
ocamlfind: Conflict with another package: Library dllcore_stubs.so is already installed

then the second time it works (had to restart also for failures in dependencies like pipebang, and ounit too)

[samoht]

It seems that you have installed OCaml with OPAM (or you don't have ocaml in your PATH). Is the contents of your CAML_LD_LIBRARY_PATH seems to be the one you'd expect ?

[samoht]

(I've pushed a fix for you first error)

[samoht]

Or you have a very old ~/.opam tree (with a bad /.opam/compilers/system.comp). Mine looks like:

opam-version: "1"
name: "system"
version: "4.00.1"
packages: ["base-unix" "base-bigarray" "base-threads"]
env: [
  [CAML_LD_LIBRARY_PATH = "%{lib}%/stublibs:/usr/local/lib/ocaml/stublibs"]
]
preinstalled: true

[smondet]

Indeed, I had removed the system compiler. I will try again later with a fresh .opam/.

PS: I always do: install ocaml in /tmp, compile opam with it, then opam switch <another one> and opam switch remove system and delete the initial ocaml installation.

[smondet]

Hi, I still get the first error (with tag 0.9.3):

I just did

opam init
opam switch --yes 4.00.1
opam switch remove system
opam upgrade --yes

and now:

opam switch
'opam switch' failed.
Fatal error: exception File "src/client/opamSwitchCommand.ml", line 30, characters 20-26: Assertion failed

[smondet]

If I put back an ocaml compiler in the $PATH, then it works again:

 $ opam switch
4.00.1  C 4.00.1                     Official 4.00.1 release
--     -- 3.11.2                     Official 3.11.2 release
--     -- 3.12.1                     Official 3.12.1 release
.... etc. ....
--     -- 4.01.0dev+trunk            latest trunk snapshot
--     -- system                     System compiler (4.00.1)

[samoht]

The Fatal error: exception File "src/client/opamSwitchCommand.ml", line 30, characters 20-26: Assertion failed has unfortunately shipped with 0.9.3 but it is fixed in 0.9.4. So closing the issue (btw, 0.9.4 also containts some solver heuristics improvements).