Concretization fails with strange error with deprecated versions

[hernando]

Steps to reproduce

I was trying to build an application depending on glib 2.56.4 and I was having many problems with the concretization. After some research I found out that this version is not installable on its own and after some debugging I think I've found the cause.

The problem can be reproduced in develop-2024-04-07 with a simple package like this:

from spack.package import *

import spack.builder
import spack.package_base
from spack.directives import build_system

from spack.build_systems._checks import BaseBuilder

class FooPackage(spack.package_base.PackageBase):
    build_system_class = "FooPackage"
    build_system("foo")

@spack.builder.builder("foo")
class FooBuilder(BaseBuilder):
    pass


class BarPackage(spack.package_base.PackageBase):
    build_system_class = "BarPackage"
    build_system("bar")

@spack.builder.builder("bar")
class BarBuilder(BaseBuilder):
    pass


class Test(FooPackage, BarPackage):

    version("2")
    version("1", deprecated=True)

    build_system(
        conditional("foo", when="@2:"),
        conditional("bar", when="@:1"),
        default="foo",
    )

Trying to concretize test@1 gives an error that is not actionable and even looks wrong. If deprecated=True is removed from the version directive, the command works as expected. Adding --deprecated to the command line also works. This may be a duplicate of #42037, but the error is not exactly the same and the bit about variant ... when [,,] looks weird.

Error message

$ spack spec test@1
==> Error: concretization failed for the following reasons:

   1. Cannot satisfy 'test@1'
   2. Cannot satisfy 'test@1'
        required because test@1 requested explicitly 
   3. Cannot satisfy 'test@2:' and 'test@1
        required because test@1 requested explicitly 
        required because test variant build_system value foo when [, , ] 
          required because test@1 requested explicitly 

I did not add -d because it does not seems to provide additional hints and it should be easy to reproduce.

Information on your system

• Spack: 0.22.0.dev0 (54acda3)
• Python: 3.10.6
• Platform: linux-linuxmint21-zen3
• Concretizer: clingo

General information

• I have run spack debug report and reported the version of Spack/Python/Platform
• I have searched the issues of this repo and believe this is not a duplicate
• I have run the failing commands in debug mode and reported the output