bug#54747: 28.1.50; package.el - Better error message if newer Emacs is required

[Daniel Mendler <mail@daniel-mendler.de>]

On 4/8/22 14:51, Lars Ingebrigtsen wrote:
> And the `i' command just skips it, so that works, at least.  And using
> `M-x package-install' on it just says
> 
> Package ‘gitignore-mode-1.1.0’ is unavailable
> 
> But I haven't tried this in Emacs 28.

I just tried it again on 28. Yes, `i' skips the "imcompat" package for
me too, but `package-install' still installs the package without any
complaints.

One such "incompat" package where this happens is for example satchel
from GNU ELPA. Maybe the "incompat" label is incorrect?

>> Regarding the error messages - I think even experienced users could
>> profit from slightly improved error messages which explain dependency
>> resolution failure.
>>
>> - Package X version V requires package Y version W, which is
>> unavailable. The newest available version of Y is W'.
>> - Package X version V requires package Y, which is unavailable. The
>> package Y cannot be found in the archives.
>> - Package X version V requires package Y version W, which cannot be
>> installed. The dependency Z of Y cannot be satisfied.
>> - ...
> 
> It does say some of that.  Reading the code:

Very well then. I also saw that you added the improved error message if
a newer Emacs version is required. Thank you! From my side the issue
about the error message can be closed.

Daniel