Re: What's the right way to extract a package's version from the header metadata?

["Bozhidar Batsov" <bozhidar@batsov.dev>]

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Thanks for the quick response! It would be great indeed if  `package-get-version` worked in more cases and we could just consider it the canonical solution the version extraction problem. 

On Wed, Dec 29, 2021, at 9:42 AM, Stefan Monnier wrote:
> > Basically I want to extract the package version from the *Version:*
> >  header instead of having to duplicate it. I know of
> >  package-get-package-version, but I assume it won't work for people
> >  who didn't install my packages via package.el.  
> 
> `package-get-version` should work but only if they had the foresight to
> put it in a directory whose name ends in "-<version>" or whose name is
> just `cider` (i.e. the name of your package) :-(
> 
> The patch below (which I plan to push to `master` soon) should make it
> work in other cases as well if the call is in the same file where the
> `Version:` can be found.
> 
> 
>         Stefan
> 
> 
> diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
> index 9b6b5d4dc0d..d477266a7ef 100644
> --- a/lisp/emacs-lisp/package.el
> +++ b/lisp/emacs-lisp/package.el
> @@ -4077,7 +4077,9 @@ package-get-version
>    "Return the version number of the package in which this is used.
> Assumes it is used from an Elisp file placed inside the top-level directory
> of an installed ELPA package.
> -The return value is a string (or nil in case we can't find it)."
> +The return value is a string (or nil in case we can't find it).
> +It works in more cases if the call is in the file which contains
> +the `Version:' header."
>    ;; In a sense, this is a lie, but it does just what we want: precompute
>    ;; the version at compile time and hardcodes it into the .elc file!
>    (declare (pure t))
> @@ -4096,6 +4098,7 @@ package-get-version
>        (let* ((pkgdir (file-name-directory file))
>               (pkgname (file-name-nondirectory (directory-file-name pkgdir)))
>               (mainfile (expand-file-name (concat pkgname ".el") pkgdir)))
> +        (unless (file-readable-p mainfile) (setq mainfile file))
>          (when (file-readable-p mainfile)
>            (require 'lisp-mnt)
>            (with-temp-buffer
> 
> 

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