On 11/12/17 09:47, Ludovic Courtès wrote:

>> 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 python@2 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: python@2.7.13 /gnu/store/vysfxizaddh1q8s5qjgbdkzxx0585dzi-python-2.7.13
>> guix package: error:   second entry: python@3.5.3 /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: cairo@1.14.10 /gnu/store/c4vl4hw5jccg0b23sfvs0kdnfdbxdlgm-cairo-1.14.10
>> guix package: error:    ... propagated from guile-cairo@1.4.1
>> guix package: error:   second entry: cairo@1.14.10 /gnu/store/nwxv9s2q8pi0m6gn6fyidpj8442dwp6f-cairo-1.14.10
>> guix package: error:    ... propagated from cairomm@1.12.2
>> 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.

That's Ludo, that's great!