bug#58419: Grafting order depends on store connection state

[Ludovic Courtès]

Hi,

Josselin Poiret <dev@jpoiret.xyz> skribis:

> (let ((right (with-store store (run-with-store store (package->derivation
>                                                       (specification->package
>                                                        "password-store")))))
>       (wrong (with-store store (run-with-store store (mbegin %store-monad
>                                                        (package->derivation
>                                                         
> (specification->package
>                                                          "texlive-bin"))
>                                                        (package->derivation
>                                                         
> (specification->package
>                                                          
> "password-store")))))))
>   (pk right)
>   (pk wrong))
>
> Both derivations differ even though they ideally should be identical,
> apparently git doesn't appear in the same place in the grafting
> derivation.

Right:

--- #<buffer 
a5dybalrk4xh8wfh2szja17g70x1d7l4-password-store-1.7.4-guile-builder>
+++ #<buffer 
fb7dvwb1v8bqyl1dspcq7db4qgw4qnm8-password-store-1.7.4-guile-builder>
@@ -19,17 +19,17 @@
       ("x" . "/gnu/store/3bpq5knfvzhxhqfwzqm9br917nz7r0yp-gnupg-2.2.32")
       ("x" . "/gnu/store/31ffp5lszf1g7h1zw750w621cm14hxlr-util-linux-2.37.2")
       ("x" . "/gnu/store/zpw3l0y7sq3ag3fmq001x22bdpalw1fy-xclip-0.13")
-      ("x" . "/gnu/store/f686n3snbkbbf41g7hqyb75dymnckr3z-git-2.37.3")
       ("x" . "/gnu/store/g8qm4vq1f9v81zg8aazkiaf1j3wb8w0s-dmenu-5.1")
       ("x" . 
"/gnu/store/mk4514a1rjf6mqp0z46kzh80z7j1mhbs-xdotool-3.20211022.1")
       ("x" . "/gnu/store/vmwvxj3ksnmck2cfwsgm9dfi9n41050x-wl-clipboard-2.0.0")
+      ("x" . "/gnu/store/f686n3snbkbbf41g7hqyb75dymnckr3z-git-2.37.3")
       ("x" . "/gnu/store/0jlw8kk0ll25lzbz939jaz4sbfkr8gqj-gnupg-2.2.32")
       ("x" . "/gnu/store/a8k9s0wpf0f3l7nwsscjhnbs5wrn2y1q-util-linux-2.37.2")
       ("x" . "/gnu/store/4vh3qdhsq6misl3vvgm39zdh4sflz4s0-xclip-0.13")
-      ("x" . "/gnu/store/svj9wb4jcb701g3fjf0cmi87rv85sx0x-git-2.37.3")
       ("x" . "/gnu/store/h647qh34g8afyy99gbkngavvlm2p14vn-dmenu-5.1")
       ("x" . 
"/gnu/store/n6gsqfcc51m4flr21p8szzic5yh1fpfb-xdotool-3.20211022.1")
-      ("x" . 
"/gnu/store/k28gncxkgxy3hn8qzwylsazc00pwr71s-wl-clipboard-2.0.0"))))
+      ("x" . "/gnu/store/k28gncxkgxy3hn8qzwylsazc00pwr71s-wl-clipboard-2.0.0")
+      ("x" . "/gnu/store/svj9wb4jcb701g3fjf0cmi87rv85sx0x-git-2.37.3"))))
   (unsetenv "GUILE_LOAD_COMPILED_PATH")
   (unsetenv "LD_LIBRARY_PATH"))
 (exit
@@ -44,10 +44,10 @@
           (("/gnu/store/3bpq5knfvzhxhqfwzqm9br917nz7r0yp-gnupg-2.2.32" . 
"/gnu/store/0jlw8kk0ll25lzbz939jaz4sbfkr8gqj-gnupg-2.2.32")
            ("/gnu/store/31ffp5lszf1g7h1zw750w621cm14hxlr-util-linux-2.37.2" . 
"/gnu/store/a8k9s0wpf0f3l7nwsscjhnbs5wrn2y1q-util-linux-2.37.2")
            ("/gnu/store/zpw3l0y7sq3ag3fmq001x22bdpalw1fy-xclip-0.13" . 
"/gnu/store/4vh3qdhsq6misl3vvgm39zdh4sflz4s0-xclip-0.13")
-           ("/gnu/store/f686n3snbkbbf41g7hqyb75dymnckr3z-git-2.37.3" . 
"/gnu/store/svj9wb4jcb701g3fjf0cmi87rv85sx0x-git-2.37.3")
            ("/gnu/store/g8qm4vq1f9v81zg8aazkiaf1j3wb8w0s-dmenu-5.1" . 
"/gnu/store/h647qh34g8afyy99gbkngavvlm2p14vn-dmenu-5.1")
            ("/gnu/store/mk4514a1rjf6mqp0z46kzh80z7j1mhbs-xdotool-3.20211022.1" 
. "/gnu/store/n6gsqfcc51m4flr21p8szzic5yh1fpfb-xdotool-3.20211022.1")
-           ("/gnu/store/vmwvxj3ksnmck2cfwsgm9dfi9n41050x-wl-clipboard-2.0.0" . 
"/gnu/store/k28gncxkgxy3hn8qzwylsazc00pwr71s-wl-clipboard-2.0.0")))
+           ("/gnu/store/vmwvxj3ksnmck2cfwsgm9dfi9n41050x-wl-clipboard-2.0.0" . 
"/gnu/store/k28gncxkgxy3hn8qzwylsazc00pwr71s-wl-clipboard-2.0.0")
+           ("/gnu/store/f686n3snbkbbf41g7hqyb75dymnckr3z-git-2.37.3" . 
"/gnu/store/svj9wb4jcb701g3fjf0cmi87rv85sx0x-git-2.37.3")))
          (map
           (match-lambda
             ((name . file)

If we squint a bit, we realize it’s the same thing but in a different
order, which is good news: it’s functionally equivalent.

The downside is obvious: it’s stupidly non-deterministic, and we can end
up building the same grafts multiple times.

The order differs in two places: in the definition of ‘%build-inputs’,
and in the definition of the ‘mapping’ variable.  This can be solved by
sorting things in the right place, but that needs some thought.

To be continued…

Ludo’.