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Re: Mysterious error while refactoring guix/scripts/system.scm
From: |
Ludovic Courtès |
Subject: |
Re: Mysterious error while refactoring guix/scripts/system.scm |
Date: |
Mon, 29 Aug 2016 17:53:03 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Hi Chris, and sorry for the delay!
Chris Marusich <address@hidden> skribis:
> Backtrace:
> In ice-9/boot-9.scm:
> 157: 15 [catch #t #<catch-closure 26304a0> ...]
> In unknown file:
> ?: 14 [apply-smob/1 #<catch-closure 26304a0>]
> In ice-9/boot-9.scm:
> 63: 13 [call-with-prompt prompt0 ...]
> In ice-9/eval.scm:
> 432: 12 [eval # #]
> In ice-9/boot-9.scm:
> 2401: 11 [save-module-excursion #<procedure 264f940 at
> ice-9/boot-9.scm:4045:3 ()>]
> 4050: 10 [#<procedure 264f940 at ice-9/boot-9.scm:4045:3 ()>]
> 1724: 9 [%start-stack load-stack ...]
> 1729: 8 [#<procedure 2668ea0 ()>]
> In unknown file:
> ?: 7 [primitive-load "/root/guix/scripts/guix"]
> In guix/ui.scm:
> 1209: 6 [run-guix-command system "list-generations"]
> In ice-9/boot-9.scm:
> 157: 5 [catch srfi-34 #<procedure 52af180 at guix/ui.scm:425:2 ()> ...]
> 157: 4 [catch system-error ...]
> In guix/scripts/system.scm:
> 884: 3 [#<procedure 52ae750 at guix/scripts/system.scm:876:2 ()>]
> 818: 2 [process-command list-generations () ...]
> In guix/store.scm:
> 1182: 1 [run-with-store # ...]
> In unknown file:
> ?: 0 [#<unspecified> #<build-daemon 256.15 52b8e80>]
>
> ERROR: In procedure #<unspecified>:
> ERROR: Wrong type to apply: #<unspecified>
This means that we’re trying to invoke #<unspecified>, but
#<unspecified> is not a procedure.
Note that this is from within ‘run-to-store’, which is the procedure to
“run” a monadic value. So in effect, what happened is equivalent to:
--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> ,use(guix monads)
scheme@(guile-user)> ,use(guix store)
scheme@(guile-user)> (with-store s
(run-with-store s *unspecified*))
ERROR: In procedure #<unspecified>:
ERROR: Wrong type to apply: #<unspecified>
--8<---------------cut here---------------end--------------->8---
The bug here is in fact a type error: ‘run-with-store’ expect a monadic
value, but what we have here is a regular value.
To “fix” it, we need:
--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> (with-store s
(run-with-store s
(with-monad %store-monad (return *unspecified*))))
--8<---------------cut here---------------end--------------->8---
… where ‘return’ procedure a monadic value from a normal value.
In your case, ‘list-generations’ is not a monadic procedure (a procedure
that returns a monadic value), so in this patch:
(run-with-store store
…
(list-generations))
… triggers this very type error.
I imagine this may be more than you wanted to learn. ;-)
Monads in a dynamically typed setting are kinda annoying because of
this.
> (define (process-command command args opts)
> "Process COMMAND, one of the 'guix system' sub-commands. ARGS is its
> argument list and OPTS is the option alist."
> - (case command
> - ((list-generations)
> - ;; List generations. No need to connect to the daemon, etc.
> - (let ((pattern (match args
> - (() "")
> - ((pattern) pattern)
> - (x (leave (_ "wrong number of arguments~%"))))))
> - (list-generations pattern)))
> - (else
> - (process-action command args opts))))
> + (with-store store
> + (set-build-options-from-command-line store opts)
> +
> + (run-with-store store
> + (mbegin %store-monad
> + (set-guile-for-build (default-guile))
> + (case command
> + ((list-generations)
> + (let ((pattern (match args
> + (() "")
> + ((pattern) pattern)
> + (x (leave (_ "wrong number of arguments~%"))))))
> + (list-generations pattern)))
> + (else
> + (process-action command args opts))))
> + #:system (assoc-ref opts 'system))))
As the comment above suggests, the idea here was to avoid connecting to
the daemon for operations that do not need it, such as
‘list-generations’. I think we should preserve this property.
Thanks for your work! I’m sorry this is more painful than I thought.
:-/
Ludo’.