Fixed kernel compile sccache caching

a little bit of chatgpt5.4 slop has fixed the kernel caching with sccache. Good stuff.

custom/modules/kernel.nix

@@ -33,6 +33,7 @@ pkgs.callPackage (
   { buildLinux, ... }@args:
   let
     llvm = pkgs.llvmPackages_latest;
+    rust = pkgs.rustc-unwrapped;
 
     # buildLinux uses common-flags.nix which sets CC to the *unwrapped* compiler:
     #   CC=${lib.getExe stdenv.cc.cc}
@@ -43,31 +44,54 @@ pkgs.callPackage (
     buildPkgs = args.buildPackages or pkgs.buildPackages;
     realHostCC = lib.getExe' buildPkgs.stdenv.cc "${buildPkgs.stdenv.cc.targetPrefix}cc";
     realHostCXX = lib.getExe' buildPkgs.stdenv.cc "${buildPkgs.stdenv.cc.targetPrefix}c++";
+    realRustc = lib.getExe rust;
+    realHostRustc = realRustc;
 
     clangSccache = pkgs.writeShellScriptBin "clang" ''
       set -euo pipefail
-      : "''${SCCACHE_ENFORCE_MARKER:?SCCACHE_ENFORCE_MARKER is not set}"
-      : > "''${SCCACHE_ENFORCE_MARKER}"
       export SCCACHE_DIR=${lib.escapeShellArg sccacheDir}
+      if [ -n "''${SCCACHE_ENFORCE_MARKER-}" ]; then
+        : > "''${SCCACHE_ENFORCE_MARKER}"
+      fi
       exec ${pkgs.sccache}/bin/sccache ${realClang} "$@"
     '';
 
     hostccSccache = pkgs.writeShellScriptBin "cc" ''
       set -euo pipefail
-      : "''${SCCACHE_ENFORCE_MARKER:?SCCACHE_ENFORCE_MARKER is not set}"
-      : > "''${SCCACHE_ENFORCE_MARKER}"
       export SCCACHE_DIR=${lib.escapeShellArg sccacheDir}
+      if [ -n "''${SCCACHE_ENFORCE_MARKER-}" ]; then
+        : > "''${SCCACHE_ENFORCE_MARKER}"
+      fi
       exec ${pkgs.sccache}/bin/sccache ${realHostCC} "$@"
     '';
 
     hostcxxSccache = pkgs.writeShellScriptBin "c++" ''
       set -euo pipefail
-      : "''${SCCACHE_ENFORCE_MARKER:?SCCACHE_ENFORCE_MARKER is not set}"
-      : > "''${SCCACHE_ENFORCE_MARKER}"
       export SCCACHE_DIR=${lib.escapeShellArg sccacheDir}
+      if [ -n "''${SCCACHE_ENFORCE_MARKER-}" ]; then
+        : > "''${SCCACHE_ENFORCE_MARKER}"
+      fi
       exec ${pkgs.sccache}/bin/sccache ${realHostCXX} "$@"
     '';
 
+    rustcSccache = pkgs.writeShellScriptBin "rustc" ''
+      set -euo pipefail
+      export SCCACHE_DIR=${lib.escapeShellArg sccacheDir}
+      if [ -n "''${SCCACHE_ENFORCE_MARKER-}" ]; then
+        : > "''${SCCACHE_ENFORCE_MARKER}"
+      fi
+      exec ${pkgs.sccache}/bin/sccache ${realRustc} "$@"
+    '';
+
+    hostrustcSccache = pkgs.writeShellScriptBin "rustc" ''
+      set -euo pipefail
+      export SCCACHE_DIR=${lib.escapeShellArg sccacheDir}
+      if [ -n "''${SCCACHE_ENFORCE_MARKER-}" ]; then
+        : > "''${SCCACHE_ENFORCE_MARKER}"
+      fi
+      exec ${pkgs.sccache}/bin/sccache ${realHostRustc} "$@"
+    '';
+
     structuredExtraConfig' =
       (with lib.kernel; {
         LTO_CLANG_THIN = yes;
@@ -97,29 +121,41 @@ pkgs.callPackage (
           "CC=${lib.getExe clangSccache}"
           "HOSTCC=${lib.getExe hostccSccache}"
           "HOSTCXX=${lib.getExe hostcxxSccache}"
+          "RUSTC=${lib.getExe rustcSccache}"
+          "HOSTRUSTC=${lib.getExe hostrustcSccache}"
         ];
 
-      # Enforce that the wrappers were actually invoked at least once.
-      # sccache is a compiler wrapper; this is the contract we’re enforcing. :contentReference[oaicite:4]{index=4}
+      # Start with clean stats so the build-phase check reports only this build.
       preBuild =
         (args.preBuild or "")
         + lib.optionalString enforceSccache ''
-          export SCCACHE_ENFORCE_MARKER="$NIX_BUILD_TOP/.sccache-used"
-          rm -f "$SCCACHE_ENFORCE_MARKER"
           ${pkgs.sccache}/bin/sccache --start-server || true
           ${pkgs.sccache}/bin/sccache --zero-stats || true
         '';
 
-      postBuild =
-        (args.postBuild or "")
-        + lib.optionalString enforceSccache ''
-          if [ ! -e "$SCCACHE_ENFORCE_MARKER" ]; then
-            echo "FATAL: sccache enforcement failed: compiler wrappers were not invoked."
-            echo "This means buildLinux did not use your CC/HOSTCC overrides."
-            exit 1
-          fi
-          ${pkgs.sccache}/bin/sccache --show-stats --stats-format text || true
-        '';
+      buildPhase =
+        if enforceSccache then
+          ''
+            runHook preBuild
+            export SCCACHE_ENFORCE_MARKER="$NIX_BUILD_TOP/.sccache-used"
+            rm -f "$SCCACHE_ENFORCE_MARKER"
+            make "''${makeFlags[@]}" "''${buildFlags[@]}"
+            if [ ! -e "$SCCACHE_ENFORCE_MARKER" ]; then
+              echo "FATAL: sccache enforcement failed during buildPhase: compiler wrappers were not invoked."
+              echo "This means the build stage did not use your CC/HOSTCC/HOSTCXX/RUSTC/HOSTRUSTC overrides."
+              exit 1
+            fi
+            ${pkgs.sccache}/bin/sccache --show-stats --stats-format text || true
+            runHook postBuild
+          ''
+        else
+          (args.buildPhase or ''
+            runHook preBuild
+            make "''${makeFlags[@]}" "''${buildFlags[@]}"
+            runHook postBuild
+          '');
+
+      postBuild = args.postBuild or "";
 
       structuredExtraConfig = structuredExtraConfig';
 

flake.nix

@@ -61,7 +61,7 @@
           kernel-src = inputs.kernel-src;
         };
         modules = [
-          # ./custom/modules
+          ./custom/modules
           ragenix.nixosModules.default
           niri-flake.nixosModules.niri
           nix-index-database.nixosModules.default