bug#29255: "Profile contains conflicting entries" could be more helpful

[Ludovic Courtès]

Hello!

address@hidden (Ludovic Courtès) skribis:

> Ricardo Wurmus <address@hidden> skribis:
>
>> In this case it is not entirely clear that the existing python-requests
>> package in the profile is “old”.  The version looks the same and the
>> hash is opaque.
>>
>> Would it be possible to record something about the Guix version that was
>> used to install a package?  Then we could say:
>>
>>   An older variant of python-requests is installed in this profile
>>   (propagated from package “foo-bar”) and conflicts with a newer variant
>>   (propagated from package “python-twine”).
>
> When the version numbers are the same, we cannot tell whether a variant
> is “older”, we can just tell that it’s different.  Also, I find it
> useful to see the propagation stack as is currently the case.
>
> With the patch below, I get:
>
> $ ./pre-inst-env guix package -p foo -i address@hidden python
> The following packages will be installed:
>    python     2.7.13  
> /gnu/store/vysfxizaddh1q8s5qjgbdkzxx0585dzi-python-2.7.13
>    python     3.5.3   /gnu/store/m4rdgmvdqcxs2zhv42idnz1s1w391i8j-python-3.5.3
>
> guix package: error: profile contains conflicting entries for python:out
> guix package: error:   first entry: address@hidden 
> /gnu/store/vysfxizaddh1q8s5qjgbdkzxx0585dzi-python-2.7.13
> guix package: error:   second entry: address@hidden 
> /gnu/store/m4rdgmvdqcxs2zhv42idnz1s1w391i8j-python-3.5.3
> hint: You cannot have two different versions or variants of `python' in the 
> same profile.
>
>
> and:
>
> $ ./pre-inst-env guix package -i guile-cairo -p foo --no-grafts
> The following package will be installed:
>    guile-cairo        1.4.1   
> /gnu/store/dsdbp9sqla6zz2skljlcr5zfjyzvargf-guile-cairo-1.4.1
>
> guix package: error: profile contains conflicting entries for cairo:out
> guix package: error:   first entry: address@hidden 
> /gnu/store/c4vl4hw5jccg0b23sfvs0kdnfdbxdlgm-cairo-1.14.10
> guix package: error:    ... propagated from address@hidden
> guix package: error:   second entry: address@hidden 
> /gnu/store/nwxv9s2q8pi0m6gn6fyidpj8442dwp6f-cairo-1.14.10
> guix package: error:    ... propagated from address@hidden
> hint: Try upgrading both `guile-cairo' and `cairomm', or remove one of them 
> from the profile.

I’ve pushed the patch as commit
3b80b81358b3861ca3794105c8eb4395df97846b.  Hopefully these hints help
users get on the right track, and we can always adjust them.

Thanks,
Ludo’.