From 8e5ac55fb1dea52932f38bbc4502133a4dcc2a09 Mon Sep 17 00:00:00 2001
From: phaer <hello@phaer.org>
Date: Tue, 1 Apr 2025 11:52:18 +0200
Subject: [PATCH] nixos-rebuild: don't eval closure before validating variant

Because we want to be able to list variants even if one of them might
not eval correctly.

The eager evaluation was caused by us querying for the resulting image
file name to early and is fixed by calling nix-instantiate/nix eval
twice now, once for the variants, once for the image file name.

fixes #394626
---
 .../linux/nixos-rebuild/nixos-rebuild.sh      | 34 +++++++++++++++----
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh b/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh
index c4766a7e685d..6c61b3c7a503 100755
--- a/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh
+++ b/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh
@@ -835,28 +835,50 @@ if [ -z "$rollback" ]; then
                 "let
                     value = import \"$(realpath $buildFile)\";
                     set = if builtins.isFunction value then value {} else value;
-                in builtins.mapAttrs (n: v: v.passthru.filePath) set.${attr:+$attr.}config.system.build.images" \
+                in builtins.attrNames set.${attr:+$attr.}config.system.build.images" \
                 "${extraBuildFlags[@]}"
             )"
         elif [[ -z $flake ]]; then
             variants="$(
                 runCmd nix-instantiate --eval --strict --json --expr \
-                "with import <nixpkgs/nixos> {}; builtins.mapAttrs (n: v: v.passthru.filePath) config.system.build.images" \
+                "with import <nixpkgs/nixos> {}; builtins.attrNames config.system.build.images" \
                 "${extraBuildFlags[@]}"
             )"
         else
             variants="$(
                 runCmd nix "${flakeFlags[@]}" eval --json \
                 "$flake#$flakeAttr.config.system.build.images" \
-                --apply "builtins.mapAttrs (n: v: v.passthru.filePath)" "${evalArgs[@]}" "${extraBuildFlags[@]}"
+                --apply "builtins.attrNames" "${evalArgs[@]}" "${extraBuildFlags[@]}"
             )"
         fi
-        if ! echo "$variants" | jq -e --arg variant "$imageVariant" "keys | any(. == \$variant)" > /dev/null; then
+        if ! echo "$variants" | jq -e --arg variant "$imageVariant" "any(. == \$variant)" > /dev/null; then
             echo -e "Please specify one of the following supported image variants via --image-variant:\n" >&2
-            echo "$variants" | jq -r '. | keys | join ("\n")'
+            echo "$variants" | jq -r 'join ("\n")'
             exit 1
         fi
-        imageName="$(echo "$variants" | jq -r --arg variant "$imageVariant" ".[\$variant]")"
+
+        if [[ -z $buildingAttribute ]]; then
+            imageName="$(
+                runCmd nix-instantiate --eval --strict --json --expr \
+                "let
+                    value = import \"$(realpath $buildFile)\";
+                    set = if builtins.isFunction value then value {} else value;
+                in set.${attr:+$attr.}config.system.build.images.$imageVariant.v.passthru.filePath" \
+                "${extraBuildFlags[@]}"
+            )"
+        elif [[ -z $flake ]]; then
+            imageName="$(
+                runCmd nix-instantiate --eval --strict --json --expr \
+                "with import <nixpkgs/nixos> {}; config.system.build.images.$imageVariant.passthru.filePath" \
+                "${extraBuildFlags[@]}"
+            )"
+        else
+            imageName="$(
+                runCmd nix "${flakeFlags[@]}" eval --json \
+                "$flake#$flakeAttr.config.system.build.images.$imageVariant.passthru.filePath" \
+                "${evalArgs[@]}" "${extraBuildFlags[@]}"
+            )"
+        fi
 
         if [[ -z $buildingAttribute ]]; then
             pathToConfig="$(nixBuild $buildFile -A "${attr:+$attr.}config.system.build.images.${imageVariant}" "${extraBuildFlags[@]}")"