add checks to flake.nix

Signed-off-by: Florian Brandes <florian.brandes@posteo.de>

flake.lock

@@ -1,5 +1,21 @@
 {
   "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -18,6 +34,27 @@
         "type": "github"
       }
     },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "pre-commit-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1709087332,
+        "narHash": "sha256-HG2cCnktfHsKV0s4XW83gU3F57gaTljL9KNSuG6bnQs=",
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "637db329424fd7e46cf4185293b9cc8c88c95394",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1720087678,
@@ -33,10 +70,64 @@
         "type": "indirect"
       }
     },
+    "nixpkgs-stable": {
+      "locked": {
+        "lastModified": 1718811006,
+        "narHash": "sha256-0Y8IrGhRmBmT7HHXlxxepg2t8j1X90++qRN3lukGaIk=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "03d771e513ce90147b65fe922d87d3a0356fc125",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-23.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1719082008,
+        "narHash": "sha256-jHJSUH619zBQ6WdC21fFAlDxHErKVDJ5fpN0Hgx4sjs=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "9693852a2070b398ee123a329e68f0dab5526681",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "pre-commit-hooks": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "gitignore": "gitignore",
+        "nixpkgs": "nixpkgs_2",
+        "nixpkgs-stable": "nixpkgs-stable"
+      },
+      "locked": {
+        "lastModified": 1719259945,
+        "narHash": "sha256-F1h+XIsGKT9TkGO3omxDLEb/9jOOsI6NnzsXFsZhry4=",
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "rev": "0ff4381bbb8f7a52ca4a851660fc7a437a4c6e07",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "flake-utils": "flake-utils",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "pre-commit-hooks": "pre-commit-hooks"
       }
     },
     "systems": {

flake.nix

@@ -4,12 +4,14 @@
   inputs = {
     nixpkgs.url = "nixpkgs/nixpkgs-unstable";
     flake-utils.url = "github:numtide/flake-utils";
+    pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
   };
 
   outputs =
     { self
     , nixpkgs
     , flake-utils
+    , pre-commit-hooks
     ,
     }:
     let
@@ -33,6 +35,22 @@
 
         packages.default = self.packages.${system}.smtprd-ng;
 
+        checks = {
+          pre-commit-check = pre-commit-hooks.lib.${system}.run rec {
+            src = ./.;
+            hooks = {
+              nixpkgs-fmt.enable = true;
+              autoflake.enable = true;
+              black.enable = true;
+              isort.enable = true;
+              isort.settings.flags = "--profile black";
+              pylint.enable = false; # doesn't work correctly with module imports in flake
+              detect-private-keys.enable = true;
+            };
+          };
+          app = self.packages.${system}.smtprd-ng;
+        };
+
         apps.default = {
           type = "app";
           program = "${self.packages.${system}.smtprd-ng}/bin/smtprd-ng";