[M4] cargoxx build invokes nix+cmake

src/cli/cmd_build.cpp

@@ -7,6 +7,7 @@ import cargoxx.layout;
 import cargoxx.linkdb;
 import cargoxx.lockfile;
 import cargoxx.codegen;
+import cargoxx.exec;
 
 namespace cargoxx::cli {
 
@@ -72,7 +73,36 @@ auto synthesize_lockfile(const manifest::Manifest& m,
 
 } // namespace
 
-auto cmd_build(const fs::path& project_root, bool no_build, bool /*release*/,
+namespace {
+
+auto run_nix_cmake(const fs::path& project_root, const std::vector<std::string>& cmake_args,
+                   std::string_view phase) -> util::Result<void> {
+    std::vector<std::string> args{"develop", "--command", "cmake"};
+    args.insert(args.end(), cmake_args.begin(), cmake_args.end());
+
+    auto r = exec::run("nix", args, exec::ExecOptions{
+                                        .cwd = project_root,
+                                        .env_overrides = {},
+                                        .timeout = std::nullopt,
+                                        .inherit_stdio = true,
+                                    });
+    if (!r) {
+        return std::unexpected(r.error());
+    }
+    if (r->exit_code != 0) {
+        return std::unexpected(util::Error{
+            util::ErrorCode::BuildCmakeFailed,
+            std::format("cmake {} failed (exit {})", phase, r->exit_code),
+            "", std::nullopt, std::nullopt,
+        });
+    }
+    return {};
+}
+
+} // namespace
+
+auto cmd_build(const fs::path& project_root, bool no_build, bool release,
+               std::optional<std::string> target,
                std::optional<fs::path> overlay_path) -> util::Result<void> {
     auto manifest_path = project_root / "Cargoxx.toml";
     auto m = manifest::parse(manifest_path);
@@ -124,13 +154,31 @@ auto cmd_build(const fs::path& project_root, bool no_build, bool /*release*/,
         return std::unexpected(r.error());
     }
 
-    if (!no_build) {
-        return std::unexpected(util::Error{
-            util::ErrorCode::NotImplemented,
-            "cargoxx build invocation is not implemented in this milestone",
-            "rerun with --no-build to generate files only (full build lands at M4)",
-            std::nullopt, std::nullopt,
-        });
+    if (no_build) {
+        return {};
+    }
+
+    const std::string profile = release ? "release" : "debug";
+    const std::string profile_cap = release ? "Release" : "Debug";
+    const auto build_dir = std::format("build/{}", profile);
+
+    std::vector<std::string> configure_args{
+        "-B", build_dir,
+        "-S", "build",
+        "-G", "Ninja",
+        std::format("-DCMAKE_BUILD_TYPE={}", profile_cap),
+    };
+    if (auto r = run_nix_cmake(project_root, configure_args, "configure"); !r) {
+        return std::unexpected(r.error());
+    }
+
+    std::vector<std::string> build_args{"--build", build_dir};
+    if (target) {
+        build_args.push_back("--target");
+        build_args.push_back(*target);
+    }
+    if (auto r = run_nix_cmake(project_root, build_args, "build"); !r) {
+        return std::unexpected(r.error());
     }
 
     return {};