flake: fix build with slang feature

crates/bender-slang/build.rs

@@ -45,6 +45,13 @@ fn main() {
         vec!["-std=c++20"]
     };
 
+    // Allow overriding FetchContent source directories via environment variables.
+    // This is used by Nix (and other sandboxed build systems) where network access
+    // is blocked and dependencies must be pre-fetched.
+    let slang_src_dir = std::env::var("SLANG_SRC_DIR").ok();
+    let fmt_src_dir = std::env::var("FMT_SRC_DIR").ok();
+    let mimalloc_src_dir = std::env::var("MIMALLOC_SRC_DIR").ok();
+
     // Apply cmake configuration for Slang library
     slang_lib
         .define("SLANG_INCLUDE_TESTS", "OFF")
@@ -57,6 +64,16 @@ fn main() {
         .define("CMAKE_DISABLE_FIND_PACKAGE_Boost", "ON")
         .profile(cmake_profile);
 
+    if let Some(ref dir) = slang_src_dir {
+        slang_lib.define("FETCHCONTENT_SOURCE_DIR_SLANG", dir);
+    }
+    if let Some(ref dir) = fmt_src_dir {
+        slang_lib.define("FETCHCONTENT_SOURCE_DIR_FMT", dir);
+    }
+    if let Some(ref dir) = mimalloc_src_dir {
+        slang_lib.define("FETCHCONTENT_SOURCE_DIR_MIMALLOC", dir);
+    }
+
     // Apply common defines and flags
     for (def, value) in common_cxx_defines.iter() {
         slang_lib.define(def, *value);
@@ -70,10 +87,17 @@ fn main() {
     let dst = slang_lib.build();
     // With FetchContent, cmake builds slang in a _deps subdirectory rather than
     // installing it. Point directly at the FetchContent build/source directories.
+    // When source dirs are overridden, include paths come from those instead.
     let slang_lib_dir = dst.join("build/_deps/slang-build/lib");
-    let slang_include_dir = dst.join("build/_deps/slang-src/include");
+    let slang_include_dir = match slang_src_dir {
+        Some(dir) => std::path::PathBuf::from(dir).join("include"),
+        None => dst.join("build/_deps/slang-src/include"),
+    };
     let slang_generated_include_dir = dst.join("build/_deps/slang-build/source");
-    let fmt_include_dir = dst.join("build/_deps/fmt-src/include");
+    let fmt_include_dir = match fmt_src_dir {
+        Some(dir) => std::path::PathBuf::from(dir).join("include"),
+        None => dst.join("build/_deps/fmt-src/include"),
+    };
 
     // Generate cpp/compile_flags.txt for clangd IDE support
     if !in_publish {
@@ -138,6 +162,9 @@ fn main() {
     println!("cargo:rerun-if-changed=cpp/rewriter.cpp");
     println!("cargo:rerun-if-changed=cpp/print.cpp");
     println!("cargo:rerun-if-changed=cpp/analysis.cpp");
+    println!("cargo:rerun-if-env-changed=SLANG_SRC_DIR");
+    println!("cargo:rerun-if-env-changed=FMT_SRC_DIR");
+    println!("cargo:rerun-if-env-changed=MIMALLOC_SRC_DIR");
 }
 
 // Generates cpp/compile_flags.txt so that clangd gets the correct include paths

flake.nix

@@ -18,20 +18,78 @@
       system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
-        teraTemplFilter = path: _type: builtins.match ".*src/script_fmt/.*tera" path != null;
-        benderFilter = path: type: ((craneLib.filterCargoSources path type) || (teraTemplFilter path type));
+
+        # Pre-fetched sources for bender-slang's cmake FetchContent dependencies.
+        # The Nix sandbox blocks network access, so we fetch these ourselves and
+        # inject them via FETCHCONTENT_SOURCE_DIR_* variables in build.rs.
+        slangSrc = pkgs.fetchFromGitHub {
+          owner = "MikePopoloski";
+          repo = "slang";
+          tag = "v11.0";
+          hash = "sha256-popHzwX0qwv2POAl7/qX3e//OwJRXGtSl9xogpSn2LI=";
+        };
+        fmtSrc = pkgs.fetchFromGitHub {
+          owner = "fmtlib";
+          repo = "fmt";
+          tag = "12.1.0";
+          hash = "sha256-ZmI1Dv0ZabPlxa02OpERI47jp7zFfjpeWCy1WyuPYZ0=";
+        };
+        mimallocSrc = pkgs.fetchFromGitHub {
+          owner = "microsoft";
+          repo = "mimalloc";
+          tag = "v3.3.2";
+          hash = "sha256-GZ37qQVDe9jgMb4Coe5oKvgaLTspZDlSkS5rdy1MfUU=";
+        };
 
         craneLib = crane.mkLib pkgs;
+
+        # Source filter: cargo sources + tera templates + bender-slang C++/CMake files + test fixtures
+        slangCrateFilter = path: _type:
+          builtins.match ".*/crates/bender-slang/(cpp/.*|CMakeLists\\.txt|build\\.rs)" path != null;
+        teraTemplFilter = path: _type: builtins.match ".*src/script_fmt/.*tera" path != null;
+        testFixtureFilter = path: _type: builtins.match ".*/tests/.*" path != null;
+        benderFilter = path: type:
+          (craneLib.filterCargoSources path type)
+          || (teraTemplFilter path type)
+          || (slangCrateFilter path type)
+          || (testFixtureFilter path type);
+
         src = pkgs.lib.cleanSourceWith {
           src = ./.;
           filter = benderFilter;
           name = "bender-source";
         };
 
-        bender = craneLib.buildPackage {
+        commonArgs = {
           inherit src;
           strictDeps = true;
+          nativeBuildInputs = with pkgs; [
+            cmake
+            python3
+          ];
         };
+
+        cargoArtifacts = craneLib.buildDepsOnly commonArgs;
+
+        bender = craneLib.buildPackage (commonArgs // {
+          inherit cargoArtifacts;
+
+          nativeCheckInputs = [ pkgs.gitMinimal ];
+
+          # Point build.rs at pre-fetched FetchContent sources
+          SLANG_SRC_DIR = slangSrc;
+          FMT_SRC_DIR = fmtSrc;
+          MIMALLOC_SRC_DIR = mimallocSrc;
+
+          # owo-colors wraps test assertions in ANSI codes when TERM is set,
+          # causing string-matching tests to fail in the sandbox.
+          preCheck = "export NO_COLOR=1";
+
+          postCheck = ''
+            patchShebangs --build tests
+            BENDER="$PWD/target/''${CARGO_BUILD_TARGET:-}/release/bender" tests/run_all.sh
+          '';
+        });
       in
       {
         packages = {