From 49606d943aa634938c6b74f35125e6b7a2ba2bc7 Mon Sep 17 00:00:00 2001
From: Emily <vcs@emily.moe>
Date: Fri, 18 Oct 2024 12:10:05 +0100
Subject: [PATCH] _experimental-update-script-combinators.sequence: handle
 silent scripts

Co-authored-by: Jan Tojnar <jtojnar@gmail.com>
---
 pkgs/common-updater/combinators.nix | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/pkgs/common-updater/combinators.nix b/pkgs/common-updater/combinators.nix
index dadbb1e81ca4..a774328380bb 100644
--- a/pkgs/common-updater/combinators.nix
+++ b/pkgs/common-updater/combinators.nix
@@ -120,21 +120,33 @@ rec {
     let
       scripts = scriptsNormalized;
       hasCommitSupport = lib.findSingle ({ supportedFeatures, ... }: supportedFeatures == [ "commit" ]) null null scripts != null;
+      hasSilentSupport = lib.findFirst ({ supportedFeatures, ... }: supportedFeatures == [ "silent" ]) null scripts != null;
+      # Supported features currently only describe the format of the standard output of the update script.
+      # Here we ensure that the standard output of the combined update script is well formed.
       validateFeatures =
         if hasCommitSupport then
+          # Exactly one update script declares only “commit” feature and all the rest declare only “silent” feature.
           ({ supportedFeatures, ... }: supportedFeatures == [ "commit" ] || supportedFeatures == [ "silent" ])
+        else if hasSilentSupport then
+          # All update scripts declare only “silent” feature.
+          ({ supportedFeatures, ... }: supportedFeatures == [ "silent" ])
         else
+          # No update script declares any supported feature to fail loudly on unknown features rather than silently discard them.
           ({ supportedFeatures, ... }: supportedFeatures == [ ]);
     in
 
-    assert lib.assertMsg (lib.all validateFeatures scripts) "Combining update scripts with features enabled (other than a single script with “commit” and all other with “silent”) is currently unsupported.";
+    assert lib.assertMsg (lib.all validateFeatures scripts) "Combining update scripts with features enabled (other than “silent” scripts and an optional single script with “commit”) is currently unsupported.";
     assert lib.assertMsg (builtins.length (lib.unique (builtins.map ({ attrPath ? null, ... }: attrPath) scripts)) == 1) "Combining update scripts with different attr paths is currently unsupported.";
 
     {
       command = commandsToShellInvocation (builtins.map ({ command, ... }: command) scripts);
-      supportedFeatures = lib.optionals hasCommitSupport [
-        "commit"
-      ];
+      supportedFeatures =
+        if hasCommitSupport then
+          [ "commit" ]
+        else if hasSilentSupport then
+          [ "silent" ]
+        else
+          [ ];
     };
 
   /*