Hi!
Looks like a good start!
Nikita Karetnikov <nik...@karetnikov.org> skribis:
> +(define (profile-rx profile)
> + "Return a regular expression that matches PROFILE's name and number."
> + (make-regexp (string-append "^" (regexp-quote (basename profile))
> + "-([0-9]+)")))
OK.
> +(define (profile-number profile)
> + "Return PROFILE's number. PROFILE should be an absolute filename."
Two spaces after period. Please write “file name”.
> + (match:substring (regexp-exec (profile-rx profile)
> + (basename (readlink profile))) 1))
Instead write:
(and=> (regexp-exec ...)
(cut match:substring <> 1))
So that the thing returns #f when there are is no associated profile
number. OTOH, does that ever occur?
> +(define (roll-back)
> + "Roll back to the previous profile."
Please add a ‘profile’ parameter, as for the other functions.
It should be possible to run:
$ guix-package -p foo --roll-back
> + (let* ((current-profile-number
> + (string->number (profile-number %current-profile)))
> + (previous-profile-number (number->string (1-
> current-profile-number)))
> + (previous-profile
> + (string-append %current-profile "-"
> + previous-profile-number "-link")))
> +
> + (define (switch)
> + "Switch to the previous generation."
For internal procedures, just use regular comments instead of docstrings.
> + (simple-format #t "guix-package: switching from generation ~a to ~a~%"
> + current-profile-number previous-profile-number)
> + (delete-file %current-profile)
> + (symlink previous-profile %current-profile))
It should be based on rename(2) to be atomic. See the ‘switchLink’
function in Nix for how to do it.
> + (if (= current-profile-number 1)
> + (error "there are no other profiles.") ; XXX: handle this error
Here you you use (leave (_ "no other profiles; not rolling back")).
> + (option '("roll-back") #f #f
> + (lambda args
> + (roll-back)
> + (exit 0)))
Instead of calling ‘roll-back’, just do like the other actions:
(alist-cons 'roll-back #t result)
Then ‘roll-back’ can be called from ‘process-actions’, with the right
profile passed as an argument. Perhaps other actions should be ignored
when rolling back. At any rate, you may need to split ‘process-actions’
into several procedures, for readability.
Can you add a test case in ‘tests/guix-package.sh’?
Thanks!
Ludo’.
