update nix-eval-jobs to fix its build

Also updates the validation versions of nixpkgs and lix.

flake.lock

@@ -36,11 +36,11 @@
     "lix": {
       "flake": false,
       "locked": {
-        "lastModified": 1726590994,
-        "narHash": "sha256-CrvIEzBzvvfE7jGIXBv6hSYDxv4eYeHWAwVho5WrF48=",
-        "rev": "8ab5743904a06c78153281bf61b3aa8aa451a489",
+        "lastModified": 1731164513,
+        "narHash": "sha256-WnT6MpgrMKgqV2Rs+MfU88+KO+/njELPOtGoNhoX2oA=",
+        "rev": "b967f1d5fe9d1bf58e6159e9b426c5b341489397",
         "type": "tarball",
-        "url": "https://git.lix.systems/api/v1/repos/lix-project/lix/archive/8ab5743904a06c78153281bf61b3aa8aa451a489.tar.gz?rev=8ab5743904a06c78153281bf61b3aa8aa451a489"
+        "url": "https://git.lix.systems/api/v1/repos/lix-project/lix/archive/b967f1d5fe9d1bf58e6159e9b426c5b341489397.tar.gz?rev=b967f1d5fe9d1bf58e6159e9b426c5b341489397"
       },
       "original": {
         "type": "tarball",
@@ -49,11 +49,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1726463316,
-        "narHash": "sha256-gI9kkaH0ZjakJOKrdjaI/VbaMEo9qBbSUl93DnU7f4c=",
+        "lastModified": 1730785428,
+        "narHash": "sha256-Zwl8YgTVJTEum+L+0zVAWvXAGbWAuXHax3KzuejaDyo=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "99dc8785f6a0adac95f5e2ab05cc2e1bf666d172",
+        "rev": "4aa36568d413aca0ea84a1684d2d46f55dbabad7",
         "type": "github"
       },
       "original": {

flake.nix

@@ -47,7 +47,7 @@
       {
         inherit pkgs;
         packages = {
-          default = pkgs.nixVersions.nix_2_18;
+          default = pkgs.nix;
           inherit (pkgs) nix-doc nix-eval-jobs;
         };
 
@@ -57,6 +57,7 @@
 
         checks = {
           inherit (self.packages.${system}) default nix-eval-jobs;
+          inherit (pkgs) nixos-option;
         } // lib.optionalAttrs (lib.elem system linux64BitSystems) {
           # wrongMajor intentionally not included here since it is expected to fail
           inherit (self.nixosTests.${system}) it-builds;

overlay.nix

@@ -1,16 +1,13 @@
 { lix, versionSuffix ? "" }:
 final: prev:
 let
-  # This is kind of scary to not override the nix version to pretend to be
-  # 2.18 since nixpkgs can introduce new breakage in its Nix unstable CLI
-  # usage.
-  # https://github.com/nixos/nixpkgs/blob/6afb255d976f85f3359e4929abd6f5149c323a02/nixos/modules/config/nix.nix#L121
   lixPackageFromSource = final.callPackage (lix + "/package.nix") ({
     inherit versionSuffix;
     stdenv = final.clangStdenv;
   });
 
-  # These packages depend on Nix features that Lix does not support
+  # These packages should receive CppNix since they may link to it or otherwise
+  # cause problems (or even just silly mass-rebuilds) if we give them Lix
   overridelist_upstream = [
     "attic-client"
     "devenv"
@@ -60,12 +57,37 @@ let
   # errors. This is a simple safeguard to put in at least something that might be seen.
   maybeWarnWrongMajor = x: if !(lib.hasPrefix supportedLixMajor lixPackageToUse.version) then builtins.trace wrongMajorWarning x else x;
 
-  overlay = 
+  # It is not enough to *just* throw whatever the default nix version is at
+  # anything in the "don't give lix" list, we have to *also* ensure that we
+  # give whatever upstream version as specified in the callPackage invocation.
+  #
+  # Unfortunately I don't think there is any actual way to directly query that,
+  # so we instead do something extremely evil and guess which version it
+  # probably was. This code is not generalizable to arbitrary derivations, so
+  # it will hopefully not make us cry, at least.
+  useCppNixOverlay =
     lib.genAttrs overridelist_upstream (
-      name: if (lib.functionArgs prev.${name}.override ? "nix") then prev.${name}.override {
-        nix = final.nixVersions.stable_upstream;
-      } else prev.${name}
-    ) // {
+      name:
+      if (lib.functionArgs prev.${name}.override ? "nix") then
+        let
+          # Get the two common inputs of a derivation/package.
+          inputs = prev.${name}.buildInputs ++ prev.${name}.nativeBuildInputs;
+          nixDependency = lib.findFirst
+            (drv: (drv.pname or "") == "nix")
+            final.nixVersions.stable_upstream # default to stable nix if nix is not an input
+            inputs;
+          nixMajor = lib.versions.major (nixDependency.version or "");
+          nixMinor = lib.versions.minor (nixDependency.version or "");
+          nixAttr = "nix_${nixMajor}_${nixMinor}";
+          finalNix = final.nixVersions.${nixAttr};
+        in
+        prev.${name}.override {
+          nix = finalNix;
+        }
+      else prev.${name}
+    );
+
+  overlay = useCppNixOverlay // {
     lix-overlay-present = 1;
     # used for things that one wouldn't necessarily want to update, but we
     # nevertheless shove it in the overlay and fixed-point it in case one *does*

pins.json

@@ -1 +1 @@
-{"nix-eval-jobs": {"kind": "tarball", "rev": "f8869bdcca7c1d5aaf37de3da3a4176811279a57", "nar_hash": "sha256-F/RvI9chHywnckEqHO1ggjzCayknhDnnl2kNnnVXpWg=", "locked_url": "https://git.lix.systems/api/v1/repos/lix-project/nix-eval-jobs/archive/f8869bdcca7c1d5aaf37de3da3a4176811279a57.tar.gz?rev=f8869bdcca7c1d5aaf37de3da3a4176811279a57", "url": "https://git.lix.systems/lix-project/nix-eval-jobs/archive/main.tar.gz"}}
+{"nix-eval-jobs": {"kind": "tarball", "rev": "57ddb99e781d19704f8a84036f9890e6ca554c41", "nar_hash": "sha256-9qkRZFTgbMonlBaLqL+OW6iiHLWXuBJlThISMhwQuGg=", "locked_url": "https://git.lix.systems/api/v1/repos/lix-project/nix-eval-jobs/archive/57ddb99e781d19704f8a84036f9890e6ca554c41.tar.gz?rev=57ddb99e781d19704f8a84036f9890e6ca554c41", "url": "https://git.lix.systems/lix-project/nix-eval-jobs/archive/main.tar.gz"}}