templates/basic-nix-cpp-app: init

configs/flake-parts/templates.nix

@@ -6,6 +6,10 @@
       path = ../../templates/basic-devshell;
       description = "Basic development shell template";
     };
+    basic-nix-cpp-app = {
+      path = ../../templates/basic-nix-cpp-app;
+      description = "Basic Nix program with C++ API";
+    };
     basic-nix-module-flake = {
       path = ../../templates/basic-nix-module-flake;
       description = "Basic Nix module flake template";

templates/basic-nix-cpp-app/default.nix

@@ -0,0 +1,37 @@
+{ stdenv
+, lib
+, cmake
+, meson
+, ninja
+, pkg-config
+, boost
+, nix
+, semver-cpp
+}:
+
+stdenv.mkDerivation {
+  pname = "app";
+  version = "0.1.0";
+
+  src = ./.;
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    cmake
+    boost
+    nix
+    semver-cpp
+  ];
+
+  meta = with lib; {
+    description = "Basic Nix CLI";
+    license = licenses.mit;
+    maintainers = with maintainers; [ foo-dogsquared ];
+    platforms = nix.meta.platforms;
+  };
+}

templates/basic-nix-cpp-app/meson.build

@@ -0,0 +1,11 @@
+project('app',
+  'cpp',
+  version: '0.1.0',
+  license: 'MIT',
+  meson_version: '>=0.56.0',
+  default_options: [
+    'cpp_std=c++20'
+    ]
+)
+
+subdir('src')

templates/basic-nix-cpp-app/shell.nix

@@ -0,0 +1,13 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+let
+  app = pkgs.callPackage ./. { };
+in
+pkgs.mkShell {
+  inputsFrom = [ app ];
+
+  packages = with pkgs; [
+    git
+    clang-tools
+  ];
+}

templates/basic-nix-cpp-app/src/main.cc

@@ -0,0 +1,29 @@
+// A nifty little app for resolving flakerefs to the locked input. Because the
+// C++ API is mostly unstable, this is confirmed to be working with Nix v2.18.2
+// just for reference.
+
+#include <iostream>
+
+#include <nlohmann/json.hpp>
+
+#include <nix/flake/flake.hh>
+#include <nix/shared.hh>
+#include <nix/store-api.hh>
+
+int main(int argc, char *argv[]) {
+  nix::initNix();
+
+  auto store = nix::openStore();
+
+  try {
+    nix::FlakeRef originalRef =
+        nix::parseFlakeRef(argv[1], std::nullopt, true, false);
+    auto [tree, lockedInput] = originalRef.input.fetch(store);
+    std::cout << lockedInput.to_string() << std::endl;
+  } catch (std::exception &e) {
+    std::cerr << e.what() << std::endl;
+    return EXIT_SUCCESS;
+  }
+
+  return EXIT_SUCCESS;
+}

templates/basic-nix-cpp-app/src/meson.build

@@ -0,0 +1,19 @@
+app_srcs = [
+  'main.cc',
+  ]
+
+NIX_VERSION = '>=2.17'
+
+deps = [
+  dependency('nix-cmd', version: NIX_VERSION),
+  dependency('nix-main', version: NIX_VERSION),
+  dependency('nix-expr', version: NIX_VERSION),
+  dependency('nix-store', version: NIX_VERSION),
+  ]
+
+executable('app',
+  app_srcs,
+  dependencies: deps,
+  install: true,
+  link_args: '-Wl,-lnixfetchers'
+  )