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bug#26023: [PATCH] gexp: Expose functions to allow creating derivation b
bug#26023: [PATCH] gexp: Expose functions to allow creating derivation builders.
Thu, 09 Mar 2017 11:44:54 +0100
Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux)
Roel Janssen <address@hidden> skribis:
> Ludovic Courtès writes:
>> Roel Janssen <address@hidden> skribis:
>>> Ludovic Courtès writes:
>>>> Roel Janssen <address@hidden> skribis:
>>>>> I would like to add the following two functions to the public interface
>>>>> of the gexp module.
>>>>> This makes writing custom derivation builders easier for external
>>>> Out of curiosity, how do you use them?
>>>> I’m asking because they’re not too bad but not too nice an interface
>>>> either, especially ‘load-path-expression’, and I’d expect the use cases
>>>> to be covered by ‘gexp->script’ & ‘gexp->file’.
>>> Here's how I use it:
>>> (define* (process->bash-engine-derivation proc #:key (guile
>>> "Return an executable script that runs the PROCEDURE described in PROC,
>>> PROCEDURE's imported modules in its search path."
>>> (let ((name (process-full-name proc))
>>> (exp (process-procedure proc))
>>> (out (process-output-path proc)))
>>> (let ((out-str (if out (format #f "(setenv \"out\" ~s)" out) "")))
>>> (mlet %store-monad ((set-load-path
>>> (load-path-expression (gexp-modules exp))))
>>> (call-with-output-file (ungexp output)
>>> (lambda (port)
>>> (use-modules (ice-9 pretty-print))
>>> (format port "#!~a/bin/bash~%" (ungexp bash))
>>> ;; Now that we've written all of the shell code,
>>> ;; We can start writing the Scheme code.
>>> ;; We rely on Bash for this to work.
>>> (format port "read -d '' CODE <<EOF~%")
>>> ;; The destination can be outside of the store.
>>> ;; TODO: We have to mount this location when building inside
>>> ;; a container.
>>> (format port "~a" (ungexp out-str))
>>> (format port
>>> "~%;; Code to create a proper Guile
>>> (lambda _ (pretty-print '(ungexp set-load-path)))))
>>> (format port ";; Actual code from the procedure.~%~a~%"
>>> (lambda _ (pretty-print '(ungexp exp)))))
>>> (format port "EOF~%")
>>> (format port "~a/bin/guile -c \"$CODE\"~%" (ungexp guile))
>>> (chmod port #o555)))))))))
>>> If you have a suggestion on how to avoid using them, I'd love to hear it.
>> In theory you could put the Scheme code in a separate file (created with
>> ‘gexp->script’), or avoid Bash altogether, but perhaps none of these is
>> an option?
> No, it's meant to build runnable scripts that can be run by a job
> scheduling system (Sun Grid Engine). It's configured to just run a bash
> script (yes, really bash, not just a shell script) with some additional
> syntax. (For the sake of the example, I gave a shorter version that
> "only" generates the regular bash script.
Oh, I see.
> Perhaps we can come up with a better interface for the gexp module to
> handle these cases. I will give this some thought.
In the meantime, you can go ahead and expose these two procedures, it’s
not that bad either. Please add a reference to this issue in the commit