Retries with straight.el

April 8, 2021
(emacs)

We all know, network is unreliable. I love those moments when I decide to upgrade all my Emacs packages while connected via 3G. And since I am using raxod502/straight.el, the process requires to process each repository one by one. Now imagine my frustration, when due to unstable connection it fails on one of the repositories and I need to start the process again… from the beginning.

So I say, no more, raxod502/straight.el should retry read operations over network! Unfortunately, there is no such option out of box (or at least I could not find it). Luckily, it’s Emacs!

First, we want to configure how many times we want to retry before actually failing.

(defvar elpa-straight-retry-count 3
  "Amount of retries for `straight' operations.")

Secondly, we write a ‘generic’ function that simply retries some orig-fn. It simply evaluates a function, and if it fails, tries again in a while loop. It doesn’t report intermediate failures, if you wish to, it’s easy to do. But once it gets to the final error, it signals it back to the user.

(defun elpa-straight-with-retry (orig-fn &rest args)
  "Wrapper around ORIG-FN supporting retries.

ORIG-FN is called with ARGS and retried
`elpa-straight-retry-count' times."
  (let ((n elpa-straight-retry-count)
        (res nil))
    (while (> n 0)
      (condition-case err
          (progn
            (setq res (apply orig-fn args)
                  n 0)
            res)
        (error
         (setq n (- n 1))
         (unless (> n 0)
           (signal (car err) (cdr err))))))))

Lastly, we need to wrap functions that do some networking. You see, thanks to advice-add, it’s so easy to do!

(advice-add #'straight-fetch-package
            :around
            #'elpa-straight-with-retry)
(advice-add #'straight--clone-repository
            :around
            #'elpa-straight-with-retry)

Now you might wonder, is it possible to apply elpa-straight-with-retry to other functions? Of course! Just give it a better name and enjoy your Emacs life full of retries.

Safe travels!