Re: package.el and emacs-version dependencies

[Artur Malabarba <bruce.connor.am@gmail.com>]

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If we agree this is a desirable feature, the following patch should do it.

2015-02-10 9:13 GMT+00:00 Artur Malabarba <bruce.connor.am@gmail.com>:
> Is there any code in package.el to prevent the listing of completely
> incompatible packages?
>
> If not, would this be a desirable feature, or do we prefer to always
> display everything?
>
> Context:
> I noticed that, on Emacs 24.3, package.el will list packages that
> depend on emacs-24.4, even though they are completely uninstallable.
>
> I realise package.el has changed a lot since 24.3, but I didn't find a
> straightforward way to check if this has changed, given that there are
> no packages that depend on version > 24.4 (thus my question).

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From ac2b20bd793df4b3a2b34bb0d86780a7705748b2 Mon Sep 17 00:00:00 2001
From: Artur Malabarba <bruce.connor.am@gmail.com>
Date: Tue, 10 Feb 2015 09:41:58 +0000
Subject: [PATCH] emacs-lisp/package.el: Don't list incompatible packages.

---
 lisp/ChangeLog             |  8 ++++++++
 lisp/emacs-lisp/package.el | 12 ++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index eee6744..daf00dd 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,11 @@
+2015-02-10  Artur Malabarba  <bruce.connor.am@gmail.com>
+
+	* emacs-lisp/package.el (package-menu--refresh): Don't list
+	incompatible packages.
+	(package--compatible-p): New function.  Return nil if PKG has no
+	chance of being installable.
+	(package--emacs-version-list): New variable.
+
 2015-02-10  Lars Ingebrigtsen  <larsi@gnus.org>
 
 	* net/shr.el (shr-use-fonts): New variable.
diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index c3a2061..fbde171 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -2093,6 +2093,17 @@ package PKG-DESC, add one.  The alist is keyed with PKG-DESC."
             (if (package--user-selected-p name)
                 "installed" "dependency")))))))))
 
+(defvar package--emacs-version-list (version-to-list emacs-version)
+  "`emacs-version', as a list.")
+
+(defun package--compatible-p (pkg)
+  "Return nil if PKG has no chance of being installable.
+PKG is a package-desc object.
+Currently, only checks if PKG depends on a higher `emacs-version'
+than the one being used."
+  (when-let ((version (cdr-safe (assq 'emacs (package-desc-reqs pkg)))))
+    (version-list-<= version package--emacs-version-list)))
+
 (defun package-menu--refresh (&optional packages keywords)
   "Re-populate the `tabulated-list-entries'.
 PACKAGES should be nil or t, which means to display all known packages.
@@ -2126,6 +2137,7 @@ KEYWORDS should be nil or a list of keywords."
           ;; Hide obsolete packages.
           (when (and (not (package-installed-p (package-desc-name pkg)
                                                (package-desc-version pkg)))
+                     (package--compatible-p pkg)
                      (package--has-keyword-p pkg keywords))
             (package--push pkg (package-desc-status pkg) info-list)))))
 
-- 
1.7.12.4