From 1c2fccef832e5fbf2df4162f742f76a153aa5443 Mon Sep 17 00:00:00 2001
From: Damien Cassou <damien@cassou.me>
Date: Sat, 22 Feb 2025 15:03:39 +0100
Subject: [PATCH] services.nix-gc: extract darwin agent interval code to new
 library file

---
 modules/lib/darwin.nix      | 76 +++++++++++++++++++++++++++++++++++++
 modules/lib/default.nix     |  1 +
 modules/services/nix-gc.nix | 69 ++-------------------------------
 3 files changed, 80 insertions(+), 66 deletions(-)
 create mode 100644 modules/lib/darwin.nix

diff --git a/modules/lib/darwin.nix b/modules/lib/darwin.nix
new file mode 100644
index 000000000..070cf2153
--- /dev/null
+++ b/modules/lib/darwin.nix
@@ -0,0 +1,76 @@
+{ lib }:
+let
+  intervals = [
+    "hourly"
+    "daily"
+    "weekly"
+    "monthly"
+    "semiannually"
+    "annually"
+  ];
+
+  mkCalendarInterval =
+    frequency:
+    let
+      freq = {
+        "hourly" = [ { Minute = 0; } ];
+        "daily" = [
+          {
+            Hour = 0;
+            Minute = 0;
+          }
+        ];
+        "weekly" = [
+          {
+            Weekday = 1;
+            Hour = 0;
+            Minute = 0;
+          }
+        ];
+        "monthly" = [
+          {
+            Day = 1;
+            Hour = 0;
+            Minute = 0;
+          }
+        ];
+        "semiannually" = [
+          {
+            Month = 1;
+            Day = 1;
+            Hour = 0;
+            Minute = 0;
+          }
+          {
+            Month = 7;
+            Day = 1;
+            Hour = 0;
+            Minute = 0;
+          }
+        ];
+        "annually" = [
+          {
+            Month = 1;
+            Day = 1;
+            Hour = 0;
+            Minute = 0;
+          }
+        ];
+      };
+    in
+    freq.${frequency} or null;
+
+  intervalsString = lib.concatStringsSep ", " intervals;
+
+  assertInterval = option: interval: pkgs: {
+    assertion = (!pkgs.stdenv.isDarwin) || (lib.elem interval intervals);
+    message = "On Darwin ${option} must be one of: ${intervalsString}.";
+  };
+
+  intervalDocumentation = ''
+    On Darwin it must be one of: ${intervalsString}, which are implemented as defined in {manpage}`systemd.time(7)`.
+  '';
+in
+{
+  inherit mkCalendarInterval assertInterval intervalDocumentation;
+}
diff --git a/modules/lib/default.nix b/modules/lib/default.nix
index 27fc51833..7adc71987 100644
--- a/modules/lib/default.nix
+++ b/modules/lib/default.nix
@@ -6,6 +6,7 @@ rec {
   assertions = import ./assertions.nix { inherit lib; };
 
   booleans = import ./booleans.nix { inherit lib; };
+  darwin = import ./darwin.nix { inherit lib; };
   deprecations = import ./deprecations.nix { inherit lib; };
   generators = import ./generators.nix { inherit lib; };
   gvariant = import ./gvariant.nix { inherit lib; };
diff --git a/modules/services/nix-gc.nix b/modules/services/nix-gc.nix
index a49220990..74831e13b 100644
--- a/modules/services/nix-gc.nix
+++ b/modules/services/nix-gc.nix
@@ -8,65 +8,6 @@ let
   inherit (lib) mkOption types;
 
   cfg = config.nix.gc;
-  darwinIntervals = [
-    "hourly"
-    "daily"
-    "weekly"
-    "monthly"
-    "semiannually"
-    "annually"
-  ];
-
-  mkCalendarInterval =
-    frequency:
-    let
-      freq = {
-        "hourly" = [ { Minute = 0; } ];
-        "daily" = [
-          {
-            Hour = 0;
-            Minute = 0;
-          }
-        ];
-        "weekly" = [
-          {
-            Weekday = 1;
-            Hour = 0;
-            Minute = 0;
-          }
-        ];
-        "monthly" = [
-          {
-            Day = 1;
-            Hour = 0;
-            Minute = 0;
-          }
-        ];
-        "semiannually" = [
-          {
-            Month = 1;
-            Day = 1;
-            Hour = 0;
-            Minute = 0;
-          }
-          {
-            Month = 7;
-            Day = 1;
-            Hour = 0;
-            Minute = 0;
-          }
-        ];
-        "annually" = [
-          {
-            Month = 1;
-            Day = 1;
-            Hour = 0;
-            Minute = 0;
-          }
-        ];
-      };
-    in
-    freq.${frequency} or null;
 
   nixPackage =
     if config.nix.enable && config.nix.package != null then config.nix.package else pkgs.nix;
@@ -95,8 +36,7 @@ in
 
           On Linux this is a string as defined by {manpage}`systemd.time(7)`.
 
-          On Darwin it must be one of: ${lib.concatStringsSep ", " darwinIntervals}, which are
-          implemented as defined in the manual page above.
+          $lib.hm.darwin.{intervalDocumentation}
         '';
       };
 
@@ -170,10 +110,7 @@ in
 
       (lib.mkIf pkgs.stdenv.isDarwin {
         assertions = [
-          {
-            assertion = lib.elem cfg.frequency darwinIntervals;
-            message = "On Darwin nix.gc.frequency must be one of: ${lib.concatStringsSep ", " darwinIntervals}.";
-          }
+          (lib.hm.darwin.assertInterval "nix.gc.frequency" cfg.frequency pkgs)
         ];
 
         launchd.agents.nix-gc = {
@@ -182,7 +119,7 @@ in
             ProgramArguments = [
               "${nixPackage}/bin/nix-collect-garbage"
             ] ++ lib.optional (cfg.options != null) cfg.options;
-            StartCalendarInterval = mkCalendarInterval cfg.frequency;
+            StartCalendarInterval = lib.hm.darwin.mkCalendarInterval cfg.frequency;
           };
         };
       })