Hi Tim,

I just discovered a bug in this advice.. I needed to fix the order of
packages in the new-ret list that is returned. The bug was that the order
of pkgs in new-ret was flipped compared to that in orig-ret.. so I needed
to flip it back using reverse.

Here is the fixed function:

;; http://emacs.stackexchange.com/a/26513/115
(defun modi/package-dependency-check-ignore (orig-ret)
  "Remove the `black listed packages' from ORIG-RET.

Packages listed in the let-bound `pkg-black-list' will not be auto-installed
even if they are found as dependencies.

It is known that this advice is not effective when installed packages
asynchronously using `paradox'. Below is effective on synchronous
package installations."
  (let ((pkg-black-list '(org))
        new-ret
        pkg-name)
    (dolist (pkg-struct orig-ret)
      (setq pkg-name (package-desc-name pkg-struct))
      (if (member pkg-name pkg-black-list)
          (message (concat "Package `%s' will not be installed. "
                           "See `modi/package-dependency-check-ignore'.")
                   pkg-name)
        (push pkg-struct new-ret)))
    ;; Tue Apr 11 17:48:16 EDT 2017 - kmodi
    ;; It's *very* critical that the order of packages stays the same in
NEW-RET
    ;; as in ORIG-RET. The `push' command flips the order, so use `reverse'
    ;; to flip the order back to the original.
    ;;   Without this step, you will get errors like below when installing
    ;; packages with dependencies:
    ;;   Debugger entered--Lisp error: (error "Unable to activate package
‘nim-mode’.
    ;;   Required package ‘flycheck-28’ is unavailable")
    (setq new-ret (reverse new-ret))
    new-ret))
(advice-add 'package-compute-transaction :filter-return
#'modi/package-dependency-check-ignore)

On Sat, Mar 4, 2017 at 6:44 PM Tim Cross <theophilusx@gmail.com> wrote:

> Nice and useful idea.
>
> thanks
>
> On 5 March 2017 at 09:46, Kaushal Modi <kaushal.modi@gmail.com> wrote:
>
> I have this in my config which works very well. I use this just for org :)
> I build org from its master branch, so I do not want the dependency check
> to auto-install older versions from Elpa.
>
> ;; http://emacs.stackexchange.com/a/26513/115
> (defun modi/package-dependency-check-ignore (orig-ret)
>   "Remove the `black listed packages' from ORIG-RET.
> Packages listed in the let-bound `pkg-black-list' will not be
> auto-installed
> even if they are found as dependencies.
> It is known that this advice is not effective when installed packages
> asynchronously using `paradox'. Below is effective on synchronous
> package installations."
>   (let ((pkg-black-list '(org))
>         new-ret
>         pkg-name)
>     (dolist (pkg-struct orig-ret)
>       (setq pkg-name (package-desc-name pkg-struct))
>       (if (member pkg-name pkg-black-list)
>           (message (concat "Package `%s' will not be installed. "
>                            "See `modi/package-dependency-check-ignore'.")
>                    pkg-name)
>         ;; (message "Package to be installed: %s" pkg-name)
>         (push pkg-struct new-ret)))
>     new-ret))
> (advice-add 'package-compute-transaction :filter-return
> #'modi/package-dependency-check-ignore)
>
> https://github.com/kaushalmodi/.emacs.d/blob/master/setup-packages.el
>
> On Thu, Mar 2, 2017 at 7:41 PM Tim Cross <theophilusx@gmail.com> wrote:
>
> Is there a way to specify alternative dependencies in a package?
>
> Situation: installing a package is resulting in an additional package
> being installed even though the dependencies for the package have already
> been satisfied by another package. This results in two packages being
> installed which provide overlapping functionality.
>
> Example. I have installed org-plus-contrib. I then install elfeed-org,
> which has a dependency on org. This results in the org package being
> installed, but org is already installed as part of the org-plus-contrib
> package.
>
> I'm trying to work out if this is a problem with how dependencies are
> defined in the elfeed-org package or is it a problem with how
> org-plus-conrib is specifying what dependency it satisfies? Need to know in
> order to determine where this issue needs to be logged.
>
> --
>
> Kaushal Modi
>
>
>
>
> --
> regards,
>
> Tim
>
> --
> Tim Cross
>
> --

Kaushal Modi