nix: setup sccache

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I375e0d41d42939b63a01a59d41b3fd426a6a6964

nix/shell.nix

@@ -26,18 +26,6 @@ in
     name = "pinakes-dev";
     packages =
       [
-        pkgs.taplo # TOML formatter
-        pkgs.lldb # debugger
-        pkgs.llvm
-
-        # Modern, LLVM based linking pipelime
-        llvmPackages.lld
-        llvmPackages.clang
-
-        # Additional Cargo Tooling
-        pkgs.cargo-nextest
-        pkgs.cargo-deny
-
         # Build tools
         # We use the rust-overlay to get the stable Rust toolchain for various targets.
         # This is not exactly necessary, but it allows for compiling for various targets
@@ -47,11 +35,43 @@ in
           targets = ["wasm32-unknown-unknown" "wasm32-wasip1"]; # web + plugins
         })
 
+        # Modern, LLVM based linking pipeline
+        llvmPackages.lld
+        llvmPackages.clang
+
         # Handy CLI for packaging Dioxus apps and such
         pkgs.dioxus-cli
+
+        # Additional Cargo Tooling
+        pkgs.cargo-nextest
+        pkgs.cargo-deny
+
+        #  Other tools
+        pkgs.taplo # TOML formatter
+        pkgs.lldb # debugger
+        pkgs.sccache # distributed Rust cache
       ]
       ++ runtimeDeps;
 
+    # We could do this in the NixOS configuration via ~/.config/cargo.toml
+    # or something, but this is better because it lets everyone benefit
+    # from sccache while working with Pinakes. The reason those variables
+    # are not in 'env' are that we have to use Bash, which doesn't mix well
+    # with Nix strings.
+    shellHook = ''
+      if [ -n "$SCCACHE_BIN" ]; then
+        export RUSTC_WRAPPER="$SCCACHE_BIN"
+        export SCCACHE_DIR="''${HOME}/.cache/sccache"
+        export SCCACHE_CACHE_SIZE="50G"
+        mkdir -p "$SCCACHE_DIR"
+
+        echo "sccache setup complete!"
+      fi
+
+      # Start the daemon early for slightly faster startup.
+      "$SCCACHE_BIN" --start-server >/dev/null 2>&1 || true
+    '';
+
     env = {
       # Allow Cargo to use lld and clang properly
       LIBCLANG_PATH = "${llvmPackages.libclang.lib}/lib";
@@ -64,5 +84,8 @@ in
 
       # Runtime library path for GTK/WebKit/xdotool
       LD_LIBRARY_PATH = "${lib.makeLibraryPath runtimeDeps}";
+
+      # Enable sccache for local nix develop shell
+      SCCACHE_BIN = "${pkgs.sccache}/bin/sccache";
     };
   }