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According to emacs.SE answer I am trying to make Emacs (version 25.0.92) autoload packages if they are not already installed on my computer. At my .emacs file now I have only:

(package-initialize)

(require 'package)

(setq package-archives '(("melpa" . "http://melpa.org/packages/")))

(setq my-package-list '(nyan-mode dired+))

(mapc #'package-install my-package-list)

But have an an error:

error: Package ‘auctex-’ is unavailable

What I am doing wrong?

Community
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drobnbobn
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    You are missing a (package-refresh-contents) call. If you not installing packages interatively via M-x list-packages (which automatically updates your local database for all packages available on package-archives), you need to do this refresh manually. – Kaushal Modi Mar 16 '16 at 21:05
  • I would also recommend using use-package it will install missing packages and their dependencies. It is really great! – Jules Mar 16 '16 at 22:08
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    I'd also recommend you don't remove the default gnu archive, like you do. – Stefan Mar 17 '16 at 13:29

2 Answers2

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As @JulesTamagnan said, you should not use setq as that will totally replace the default value of package-archives. You do not need to add Melpa if you are doing it only to install auctex. But if you want to add Melpa, use add-to-list as he suggested.

(add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/") t)

The second missing piece is the call to package-refresh-contents.

Here is what I have:

(require 'package)

;; Load emacs packages and activate them
;; This must come before configurations of installed packages.
;; Don't delete this line.
(package-initialize)
;; `package-initialize' call is required before any of the below
;; can happen

(defvar my-packages '()) ; POPULATE YOUR TO-BE-INSTALLED PACKAGE LIST HERE

;; Auto install the required packages
;; https://github.com/bbatsov/prelude/blob/master/core/prelude-packages.el
;; http://toumorokoshi.github.io/emacs-from-scratch-part-2-package-management.html
(defvar modi/missing-packages '()
  "List populated at each startup that contains the list of packages that need
to be installed.")

(dolist (p my-packages)
  (when (not (package-installed-p p))
    (add-to-list 'modi/missing-packages p)))

(when modi/missing-packages
  (message "Emacs is now refreshing its package database...")
  (package-refresh-contents)
  ;; Install the missing packages
  (dolist (p modi/missing-packages)
    (message "Installing `%s' .." p)
    (package-install p))
  (setq modi/missing-packages '()))
Kaushal Modi
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  • If I got (at only first startup) some warnings like Warning (bytecomp): reference to free variable ‘nyan-animate-nyancat’ and Warning (bytecomp): assignment to free variable ‘nyan-animate-nyancat’ -- does it matter? – drobnbobn Mar 16 '16 at 21:50
  • @drobnbobn When you say "at only first startup", is that the startup when that package got installed? Or is it every time emacs starts up? If it is the latter, you should file a bug report for that package (e.g. open issue on its github) to have it fixed. – Kaushal Modi Mar 16 '16 at 22:26
  • Only when that package got installed. – drobnbobn Mar 16 '16 at 22:32
  • @drobnbobn In that case it is fine. But the dev should still try to fix those if possible. – Kaushal Modi Mar 16 '16 at 22:37
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Auctex is not in the melpa package archive it is in the gnu package archive instead of 

(setq package-archives '(("melpa" . "http://melpa.org/packages/")))

try 

(add-to-list 'package-archives
         '("melpa" . "http://melpa.org/packages/")
         'APPEND)

This will keep the gnu package repo in the list of package archives

Jules
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