chore: nix flake update

    Switched to nixpkgs-unstable
    Replaced postgresql dependency with much smaller libpq.
    Utilise new inputs.self.submodules feature to simplify flake use
    Moved apps to a separate file
    Changelog-None

Author: JosephGoulden

.github/workflows/ci.yaml

@@ -594,6 +594,25 @@ jobs:
           cat config.vars
           VALGRIND=0 uv run eatmydata pytest tests/ -vvv -n ${PYTEST_PAR} ${PYTEST_OPTS}
 
+  check-flake:
+    name: Check Nix Flake
+    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: true
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: 'recursive'
+      - name: Check Nix flake inputs
+        uses: DeterminateSystems/flake-checker-action@v8
+      - name: Install Nix
+        uses: cachix/install-nix-action@v31
+        with:
+          nix_path: nixpkgs=channel:nixos-25.05
+      - name: Check flake
+        run: nix flake check
+
   gather:
     # A dummy task that depends on the full matrix of tests, and
     # signals successful completion. Used for the PR status to pass

doc/developers-guide/developers-guide.md

@@ -62,8 +62,8 @@ The entry point is `flake.nix` in the root of the project, where the inputs and
 
 `nix develop .#rust` will create a shell env for developing rust.
 
-`nix build .?submodules=1` will build the default package (cln).
+`nix build` will build the default package (cln).
 
-`nix flake check .?submodules=1` will build the cln and rust packages. Rust tests are run during the build. There are also checks to run cargo audit and nixfmt.
+`nix flake check` will build the cln and rust packages. Rust tests are run during the build. There are also checks to run cargo audit and nixfmt.
 
-If you have nix installed you can use `nix run "git+https://github.com/hashrelay/lightning?ref=flake&submodules=1#lightningd"` to run lightningd without having to manually clone the repo. This make use of the flake output apps.
+If you have nix installed you can use `nix run "git+https://github.com/hashrelay/lightning?ref=flake#lightningd"` to run lightningd without having to manually clone the repo. This makes use of the flake output `apps`.

flake.lock

@@ -2,18 +2,23 @@
   description = "Core Lightning (CLN): A specification compliant Lightning Network implementation in C";
 
   inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
 
     flake-parts.url = "github:hercules-ci/flake-parts";
 
     crane.url = "github:ipetkov/crane";
 
-    treefmt-nix.url = "github:numtide/treefmt-nix";
+    treefmt-nix = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
 
     advisory-db = {
       url = "github:rustsec/advisory-db";
       flake = false;
     };
+
+    self.submodules = true;
   };
 
   outputs =
@@ -29,6 +34,7 @@
         inputs.treefmt-nix.flakeModule
         ./nix/pkgs/flake-module.nix
         ./nix/checks/flake-module.nix
+        ./nix/apps.nix
         ./nix/shells.nix
         ./nix/treefmt.nix
       ];
@@ -45,20 +51,6 @@
             inherit system;
             overlays = [ (final: prev: { craneLib = (inputs.crane.mkLib pkgs); }) ];
           };
-          apps = {
-            lightningd = {
-              program = "${self'.packages.cln}/bin/lightningd";
-            };
-            lightning-cli = {
-              program = "${self'.packages.cln}/bin/lightning-cli";
-            };
-            lightning-hsmtool = {
-              program = "${self'.packages.cln}/bin/lightning-hsmtool";
-            };
-            reckless = {
-              program = "${self'.packages.cln}/bin/reckless";
-            };
-          };
         };
     };
 }

flake.nix

@@ -0,0 +1,31 @@
+{ ... }:
+{
+  perSystem =
+    {
+      config,
+      pkgs,
+      system,
+      self',
+      ...
+    }:
+    {
+      apps = {
+        lightningd = {
+          program = "${self'.packages.cln}/bin/lightningd";
+          meta.description = "Core Lightning daemon";
+        };
+        lightning-cli = {
+          program = "${self'.packages.cln}/bin/lightning-cli";
+          meta.description = "Core Lightning command line interface";
+        };
+        lightning-hsmtool = {
+          program = "${self'.packages.cln}/bin/lightning-hsmtool";
+          meta.description = "Core Lightning HSM tool";
+        };
+        reckless = {
+          program = "${self'.packages.cln}/bin/reckless";
+          meta.description = "Core Lightning reckless tool";
+        };
+      };
+    };
+}

nix/apps.nix

@@ -26,26 +26,27 @@ stdenv.mkDerivation {
   # when building on darwin we need cctools to provide the correct libtool
   # as libwally-core detects the host as darwin and tries to add the -static
   # option to libtool, also we have to add the modified gsed package.
-  nativeBuildInputs =
-    [
-      autoconf
-      autogen
-      automake
-      gettext
-      gitMinimal
-      postgresql
-      libtool
-      lowdown
-      pkgconf
-      py3
-      unzip
-      which
-    ]
-    ++ lib.optionals postgresSupport [ postgresql ]
-    ++ lib.optionals stdenv.isDarwin [
-      cctools
-      darwin.autoSignDarwinBinariesHook
-    ];
+  nativeBuildInputs = [
+    autoconf
+    autogen
+    automake
+    gettext
+    gitMinimal
+    libtool
+    lowdown
+    pkgconf
+    py3
+    unzip
+    which
+  ]
+  ++ lib.optionals postgresSupport [
+    libpq
+    libpq.pg_config
+  ]
+  ++ lib.optionals stdenv.isDarwin [
+    cctools
+    darwin.autoSignDarwinBinariesHook
+  ];
 
   buildInputs = [
     gmp