bug#20863: 25.0.50; (package-install 'foo) crashes if foo is already installed

[Beni Cherniavsky-Paskin]

I'm trying to have these in my init file:

  (package-initialize)
  (package-install 'markdown-mode)  ; and more calls like this.

Unfortunately, running package-install a second time with a package that
is already installed errors with
`Wrong type argument: arrayp, markdown-mode'.

This can be reproduced with `emacs -Q' by doing:

  M-x package-initialize
  M-: (package-install 'markdown-mode)
  M-: (package-install 'markdown-mode)

This is caused by the
  (message "`%s' is already installed" (package-desc-full-name pkg))
at the end of package-install, where `pkg' is a symbol, not a
package-desc struct.

(How come this didn't bother many people before?  Rerhaps because it's
hard to run package-install interactively with an already installed
package, it doesn't complete those.)

I can send a patch but I suppose it's faster for you to fix
than the copyright assignment dance...

---

In GNU Emacs 25.0.50.2 (x86_64-pc-linux-gnu, GTK+ Version 3.14.13)
 of 2015-06-18 on lgw01-14
Windowing system distributor `The X.Org Foundation', version 11.0.11701000
System Description: Ubuntu 15.04

Configured using:
 `configure --build=x86_64-linux-gnu --prefix=/usr
 '--includedir=${prefix}/include' '--mandir=${prefix}/share/man'
 '--infodir=${prefix}/share/info' --sysconfdir=/etc --localstatedir=/var
 '--libdir=${prefix}/lib/x86_64-linux-gnu'
 '--libexecdir=${prefix}/lib/x86_64-linux-gnu' --disable-maintainer-mode
 --disable-dependency-tracking --prefix=/usr --sharedstatedir=/var/lib
 --program-suffix=-snapshot --with-x=yes --with-x-toolkit=gtk3
 'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
 -Werror=format-security' CPPFLAGS=-D_FORTIFY_SOURCE=2
 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3

Important settings:
  value of $LC_MONETARY: en_SG.UTF-8
  value of $LC_NUMERIC: en_SG.UTF-8
  value of $LC_TIME: en_SG.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Wrote /home/beni/.emacs.d/elpa/markchars-0.2.0/markchars.elc
Checking /home/beni/.emacs.d/elpa/markchars-0.2.0...
Done (Total of 1 file compiled, 2 skipped)
Quit [2 times]
Making completion list... [2 times]
Setting `package-selected-packages' temporarily since "emacs -q" would
overwrite customizations
Package `markchars-0.2.0' deleted.
Making completion list...
Package `markdown-mode+-20120829.510' deleted.
Making completion list...

Load-path shadows:
/home/beni/.emacs.d/elpa/markdown-mode-20150121.1229/markdown-mode
hides /usr/share/emacs/site-lisp/emacs-goodies-el/markdown-mode
/usr/share/emacs/site-lisp/dictionaries-common/flyspell hides
/usr/share/emacs/25.0.50/lisp/textmodes/flyspell
/usr/share/emacs/site-lisp/rst hides /usr/share/emacs/25.0.50/lisp/textmodes/rst
/usr/share/emacs/site-lisp/dictionaries-common/ispell hides
/usr/share/emacs/25.0.50/lisp/textmodes/ispell
/usr/share/emacs/site-lisp/latex-cjk-thai/thai-word hides
/usr/share/emacs/25.0.50/lisp/language/thai-word

Features:
(shadow sort mail-extr emacsbug sendmail warnings compile comint
ansi-color ring easy-mmode autoload lisp-mnt epg mm-archive message
dired format-spec rfc822 mml mml-sec mailabbrev gmm-utils mailheader
mm-decode mm-bodies mm-encode mail-utils network-stream nsm starttls
url-http tls mail-parse rfc2231 rfc2047 rfc2045 ietf-drums url-gw
url-cache url-auth url url-proxy url-privacy url-expand url-methods
url-history url-cookie url-domsuf url-util mailcap url-handlers
url-parse auth-source cl-macs cl-seq eieio byte-opt gv bytecomp
byte-compile cl-extra seq cconv eieio-core gnus-util mm-util help-fns
mail-prsvr password-cache url-vars finder-inf help-mode debug cus-edit
easymenu cus-start cus-load wid-edit cl-loaddefs pcase cl-lib package
epg-config time-date mule-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
elisp-mode lisp-mode prog-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
frame cl-generic cham georgian utf-8-lang misc-lang vietnamese tibetan
thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian
slovak czech european ethiopic indian cyrillic chinese charscript
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote dbusbind gfilenotify
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 146371 12241)
 (symbols 48 24252 0)
 (miscs 40 556 187)
 (strings 32 33783 5060)
 (string-bytes 1 893538)
 (vectors 16 17116)
 (vector-slots 8 474836 9168)
 (floats 8 213 135)
 (intervals 56 334 0)
 (buffers 976 15)
 (heap 1024 41006 1167))