On Mon, Aug 9, 2021, at 6:39 PM, Stefan Monnier wrote:
> Bozhidar Batsov [2021-08-09 17:03:21] wrote:
> > I guess that could work, although from what I gathered it operates only on
> > the current package. I was hoping to find something like an API like
> > `(package-get-version 'package-name)`.
> 
> Ah, no, we don't have such an abstraction.
> 
> Currently, you'd have to use the `package--alist` function (whose first
> call will take a bit of time to real all the <FOO>-pkg.el files) and
> then look inside its return value with `package-desc-<foo>`.

Got it, thanks!

> 
> [ That's assuming you're interested in the packages currently installed.
>   If you're interested in the packages currently activated, then you
>   have that list in `package-activated-list` but that fails to record
>   which version has been activated :-(  ]
> 
> Patches welcome to add more friendly accessors.

Will keep this in mind!

> 
> I'm also curious to know the specific context in which you need that
> info.  Is it to test at runtime whether some dependency includes
> a particular bugfix/feature ?

Yeah, something like this. Probably an overkill and it's not something I really need right now.
What I mostly needed was to extract the installed version of a snapshot package for debug purposes (useful for packages on MELPA to understand how old is the snapshot someone installed there). E.g. I print this in CIDER's REPL:

`;; CIDER 1.2.0snapshot (package: 20210729.521)`

In this case the "real" version 1.2.0-snapshot, but there's also the MELPA package version, that's basically the date the package was built.
The function you mentioned might help with this, probably in combination with lm-version. 

> 
> 
>         Stefan
> 
> 
>