A minor problem in tools/install-packages.el

[borderite]

It seems that the function exercism//install-required-packages in tools/install-packages.el assumes that if the variable package-archive-contents is not nil, the variable package-archives contains the gnu and melpa site information. This assumption does not hold in general.

For example, an emacs user has run (package-refresh-contents) without explicitly setting package-archives. In this case, package-archives contains the "gnu" and "nongnu" sites but not the "melpa" site, so that package-archive-contents is filled with the information downloaded from the "gnu" and "nongnu" sites. But two among the three required packages, mustache and string-inflection, are only avialble at the melpa site. So, running exercism//install-required-packages will result in an error message, not being able to install mustache or string-inflection, unless both of them have been already installed.

The problem can be fixed easily. Intead of checking if package-archive-contents is nil, we can directly check if the three required packages have been installed. The resulting code loos like:

(defun exercism//install-required-packages ()
  (require 'package)
  (package-initialize)
  (let ((required-packages '(mustache ht string-inflection)))
    (when (not (cl-every #'package-installed-p required-packages))
      (add-to-list
       'package-archives '("gnu" . "https://elpa.gnu.org/packages/")
       t)
      (add-to-list
       'package-archives '("melpa" . "https://melpa.org/packages/")
       t)
      (package-refresh-contents)
      (dolist (pkg required-packages)
	(package-install pkg)))))

Does this look OK? If so, shall I submit a PR?

[fapdash]

Did you run into this issue?

Usually the code is called via emacs -batch, so without init file. In that case package-archive-contents should always be nil. But I guess I also tried to run this code from my normal Emacs session and added the check for package-archive-contents. I don't remember what my thinking was there. 🤷

Feel free to open a PR, just make sure to add (require 'cl-extra), otherwise the cl-every call might fail.
cl-extra requires both cl-lib and seq, so you might as well use seq-every-p and only (require 'seq). But feel free to keep cl-every. This code isn't running in CI, we don't have to fight for every ms, I'm just being pedantic. ;)

[borderite]

@fapdash Yes, I actually got into the problem. Initially, I also thought that package-archive-contents should be nil if the code is run via emacs -batch. I even tried adding "-q" to the emacs commandline option. It seems that Emacs always getting the archived contents from ~/.emacs.d, at least, on my machine (Debian Linux 12).

I have added (require 'cl-extra) to the code. I will submit the PR shortly.

[fapdash]

Fixed via #470, closing