Subject: Re: bug#45891: [PATCH] packages: 'patch-and-repack' returns a directory when given a directory.

From: Maxim Cournoyer <[email-masked]>
Date: Fri, 15 Jan 2021 17:14:32 -0500

Hello!

Ludovic Courtès <[email-masked]> writes:

> Previously, 'patch-and-repack' would always create a tar.xz archive as a
> result, even if the input was a directory (a checkout).  This change
> reduces gratuitous CPU and storage overhead.

I like it!

Note that on core-updates, xz compression is relatively fast on modern
machines as it can do multi-threading.  About space the savings; could
the 'temporary' pristine source be cleared from the store always?  This
would prevent keeping nonfree cruft under /gnu/store until the next
garbage collection run, for those sources that are cleaned up.

> * guix/packages.scm (patch-and-repack)[tarxz-name]: Remove 'checkout?' case.
> [build](repack): New procedure, with "tar" invocation formerly at the
> top level.
> If SOURCE is a directory, call 'copy-recursively'; otherwise, call
> 'repack'.
> Change NAME to ORIGINAL-FILE-NAME when it matches 'checkout?'.
> ---
>  guix/packages.scm | 65 ++++++++++++++++++++++++++---------------------
>  1 file changed, 36 insertions(+), 29 deletions(-)
>
> Hi!
>
> This change is a followup to a recent IRC discussion: it makes
> ‘patch-and-repack’ preserve the “directoriness” of its input.
>
> It conflicts with other changes Maxim posted at
> <https://issues.guix.gnu.org/45773>, though that could be addressed.
>
> Thoughts?
>
> Ludo’.
>
> diff --git a/guix/packages.scm b/guix/packages.scm
> index 4caaa9cb79..cd2cded9ee 100644
> --- a/guix/packages.scm
> +++ b/guix/packages.scm
> @@ -1,5 +1,5 @@
>  ;;; GNU Guix --- Functional package management for GNU
> -;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 Ludovic Courtès <[email-masked]>
> +;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <[email-masked]>
>  ;;; Copyright © 2014, 2015, 2017, 2018 Mark H Weaver <[email-masked]>
>  ;;; Copyright © 2015 Eric Bavier <[email-masked]>
>  ;;; Copyright © 2016 Alex Kost <[email-masked]>
> @@ -635,11 +635,9 @@ specifies modules in scope when evaluating SNIPPET."
>  
>    (define (tarxz-name file-name)
>      ;; Return a '.tar.xz' file name based on FILE-NAME.
> -    (let ((base (cond ((numeric-extension? file-name)
> -                       original-file-name)
> -                      ((checkout? file-name)
> -                       (string-drop-right file-name 9))
> -                      (else (file-sans-extension file-name)))))
> +    (let ((base (if (numeric-extension? file-name)
> +                    original-file-name
> +                    (file-sans-extension file-name))))

This is not new code, but I'm wondering what's the purpose of
numeric-extension?  What kind of files does it expect to catch?  Also,
what happened to stripping the '-checkout' suffix that used to be done?
It doesn't seem like it will happen anymore.

>        (string-append base
>                       (if (equal? (file-extension base) "tar")
>                           ".xz"
> @@ -689,6 +687,29 @@ specifies modules in scope when evaluating SNIPPET."
>                              (lambda (name)
>                                (not (member name '("." "..")))))))
>  
> +            (define (repack directory output)
> +              ;; Write to OUTPUT a compressed tarball containing DIRECTORY.
> +              (unless tar-supports-sort?
> +                (call-with-output-file ".file_list"
> +                  (lambda (port)
> +                    (for-each (lambda (name)
> +                                (format port "~a~%" name))
> +                              (find-files directory
> +                                          #:directories? #t
> +                                          #:fail-on-error? #t)))))
> +
> +              (apply invoke #+(file-append tar "/bin/tar")
> +                     "cvfa" output
> +                     ;; Avoid non-determinism in the archive.  Set the mtime
> +                     ;; to 1 as is the case in the store (software like gzip
> +                     ;; behaves differently when it stumbles upon mtime = 0).
> +                     "--mtime=@1"
> +                     "--owner=root:0" "--group=root:0"
> +                     (if tar-supports-sort?
> +                         `("--sort=name" ,directory)
> +                         '("--no-recursion"
> +                           "--files-from=.file_list"))))
> +
>              ;; Encoding/decoding errors shouldn't be silent.
>              (fluid-set! %default-port-conversion-strategy 'error)
>  
> @@ -742,30 +763,16 @@ specifies modules in scope when evaluating SNIPPET."
>  
>                (chdir "..")
>  
> -              (unless tar-supports-sort?
> -                (call-with-output-file ".file_list"
> -                  (lambda (port)
> -                    (for-each (lambda (name)
> -                                (format port "~a~%" name))
> -                              (find-files directory
> -                                          #:directories? #t
> -                                          #:fail-on-error? #t)))))
> -              (apply invoke
> -                     (string-append #+tar "/bin/tar")
> -                     "cvfa" #$output
> -                     ;; Avoid non-determinism in the archive.  Set the mtime
> -                     ;; to 1 as is the case in the store (software like gzip
> -                     ;; behaves differently when it stumbles upon mtime = 0).
> -                     "--mtime=@1"
> -                     "--owner=root:0"
> -                     "--group=root:0"
> -                     (if tar-supports-sort?
> -                         `("--sort=name"
> -                           ,directory)
> -                         '("--no-recursion"
> -                           "--files-from=.file_list")))))))
> +              ;; If SOURCE is a directory (such as a checkout), return a
> +              ;; directory.  Otherwise create a tarball.
> +              (if (file-is-directory? #+source)
> +                  (copy-recursively directory #$output
> +                                    #:log (%make-void-port "w"))
> +                  (repack directory #$output))))))
>  
> -    (let ((name (tarxz-name original-file-name)))
> +    (let ((name (if (checkout? original-file-name)
> +                    original-file-name
> +                    (tarxz-name original-file-name))))
>        (gexp->derivation name build
>                          #:graft? #f
>                          #:system system

Was these cases (tar archive source derivation, directory source
derivation) already covered by tests under tests/packages.cm?  How did
you otherwise test it?  World rebuilding changes are not fun to test
without unit tests.

I've run that test module like this:

$ make check TESTS=tests/packages.scm SCM_LOG_DRIVER_FLAGS=' --brief=no' VERBOSE=1

with your change and it passed.

Thanks,

Maxim