[bug#68394] [PATCH python-team] gnu: python: Make the build reproducible.

[Tomas Volf <~@wolfsden.cz>]

While python build was reproducible on a single machine, once multiple
file systems entered the picture, it was no longer true.  My local builds on
BTRFS differed from build on ext4 done in a virtual machine.

The distutils library present in current python is sensitive to file system
ordering.  The solution is the same opensuse used, sorting the list of files.

With this patch, build on my machine (BTRFS) and in a guix system vm (ext4)
produce the same store item.

More info: https://bugzilla.opensuse.org/show_bug.cgi?id=1049186

* gnu/packages/python.scm (python-3.10)[arguments]<#:phases>: Add
'patch-distutils phase.

Change-Id: I0273dc0f8511a7acdcc2b462a26cc29a9756c801
---
 gnu/packages/python.scm | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/gnu/packages/python.scm b/gnu/packages/python.scm
index 51d5f598d7..319a917b4b 100644
--- a/gnu/packages/python.scm
+++ b/gnu/packages/python.scm
@@ -515,6 +515,19 @@ (define-public python-3.10
                        (substitute* "Makefile.pre.in"
                          (("-j0") "-j1")))))
                  '())
+           (add-after 'unpack 'patch-distutils
+             (lambda _
+               ;; Ensure byte_compile produces the same output regardless
+               ;; filesystem ordering.  For more information see:
+               ;; https://bugzilla.opensuse.org/show_bug.cgi?id=1049186
+               (let* ((file "Lib/distutils/util.py")
+                      (old-content (call-with-input-file file get-string-all)))
+                 (substitute* file
+                   (("^        for file in py_files:\n$")
+                    "        for file in sorted(py_files):\n"))
+                 (if (string=? old-content
+                               (call-with-input-file file get-string-all))
+                     (error "substitute did nothing, phase requires an update")))))
            (add-after 'unpack 'remove-windows-binaries
              (lambda _
                ;; Delete .exe from embedded .whl (zip) files

base-commit: 5c0f77f4241c9beac0c82deae946bfdc70b49ff0
-- 
2.41.0