IT WORKS

modules/dynamicism/dynamicism.nix

@@ -11,7 +11,6 @@ let
 
   inherit (import ./lib.nix { inherit lib; })
     typeCheck
-    convenientAttrPath
     concatFoldl
     recUpdateFoldl
     recUpdateFoldlAttrs
@@ -64,6 +63,13 @@ in
       default = { };
     };
 
+    finalEnabledSubmodules = mkOption {
+      type = options.dynamicism.for.type;
+      internal = true;
+      readOnly = true;
+      default = lib.filterAttrs (lib.const (lib.getAttr "enable")) config.dynamicism.for;
+    };
+
     finalSettings = mkOption {
       type = t.attrsOf t.raw;
       internal = true;
@@ -78,14 +84,6 @@ in
       type = t.functionTo t.raw;
       readOnly = true;
     };
-
-    doChange = mkOption {
-      type = t.functionTo t.pathInStore;
-      readOnly = true;
-      description = ''
-        The function to call to Do The Thing.
-      '';
-    };
   };
 
   # Assertions.
@@ -94,27 +92,49 @@ in
   #
   # Generic implementation.
   #
-  config.system.activationScripts."dynamicism-reset" = {
-    deps = [ "etc" "stdio" "specialfs" ];
-    text = ''
-      echo "DYNIX: removing existing systemd dropins"
-      # FIXME: do for each enabled submodule
-      if [[ -d /run/systemd/system ]]; then
-        rm -v /run/systemd/system/*/dynix-*.conf || true
+
+  config.system.activationScripts = config.dynamicism.for
+  |> lib.filterAttrs (lib.const (lib.getAttr "enable"))
+  |> lib.mapAttrs' (name: submod: let
+    forUnit = unitName: assert lib.isString unitName; let
+      dropinDir = "/run/systemd/system/${unitName}.d";
+      systemctl = lib.getExe' pkgs.systemd "systemctl";
+    in ''
+      if [[ -d "${dropinDir}" ]]; then
+        echo "Removing files in "${dropinDir}" >&2
+
+        rm -rvf "${dropinDir}/"*
+        rmdir "${dropinDir}"
+
+        ${systemctl} daemon-reload
+        ${systemctl} try-reload-or-restart "${unitName}"
       fi
     '';
-  };
+
+  in {
+    name = "dynix-reset-dynamicism-for-${name}";
+    value.deps = [ "etc" "stdio" "specialfs" "binsh" "usrbinenv" "var" "udevd" ];
+    value.text = ''
+      echo "Removing existing dynamic overrides for ${name}" >&2
+      ${submod.systemd-services-updated |> lib.map forUnit |> lib.concatStringsSep "\n"}
+    '';
+  });
+
   config.dynamicism = {
 
     applyDynamicConfiguration = {
       baseConfiguration ? builtins.getEnv "NIXOS_CONFIG",
-      newConfiguration ? baseConfiguration + "/dynamic.nix",
+      newConfiguration ? (lib.filesystem.dirOf baseConfiguration) + "/dynamic.nix",
     }: let
       locFor = appendage: lib.concatLists [
         opts.applyDynamicConfiguration.loc
         [ "(function argument)" ]
         (lib.toList appendage)
       ];
+    in
+      assert seqTrue (typeCheck (locFor "baseConfiguration") t.deferredModule baseConfiguration);
+      assert seqTrue (typeCheck (locFor "newConfiguration") t.deferredModule newConfiguration);
+    let
 
       _file = "«inline module in ${showOption opts.applyDynamicConfiguration.loc}»";
 
@@ -132,49 +152,25 @@ in
         };
       };
 
-      submodulesChanged = lib.filter (submodName:
+      submodulesChanged = nixosAfter.config.dynamicism.finalEnabledSubmodules
+      |> lib.filterAttrs (submodName: _:
         nixosBefore.config.dynamicism.for.${submodName}.finalSettings
         !=
         nixosAfter.config.dynamicism.for.${submodName}.finalSettings
-      ) (lib.attrNames config.dynamicism.for);
-    in
-      assert seqTrue (typeCheck (locFor "baseConfiguration") t.deferredModule baseConfiguration);
-      assert seqTrue (typeCheck (locFor "newConfiguration") t.deferredModule newConfiguration);
-    {
-      inherit submodulesChanged;
-    };
+      );
 
-    doChange = {
-      option,
-      value,
-      configuration ? builtins.getEnv "NIXOS_CONFIG",
-    }: let
-      loc = opts.doChange.loc ++ [ "(function argument)" "value" ];
-      option' = typeCheck loc convenientAttrPath option;
-      nixosAfter = evalNixos {
-        configuration = { config, ... }: {
-          imports = [
-            configuration
-            (lib.setAttrByPath option' (lib.mkOverride (-999) value))
-          ];
-
-          environment.systemPackages = [
-            config.dynamicism.for.gotosocial.activate
-          ];
-        };
-      };
-
-      runAllActivationScripts = nixosAfter.config.dynamicism.for
-      |> lib.filterAttrs (lib.const (lib.getAttr "enable"))
-      |> lib.mapAttrsToList (name: submod: ''
+      runForSubmodCalled = name: ''
         echo "Activating dynamic configuration for ${name}"
-        ${lib.getExe submod.activate}
-      '')
+        ${lib.getExe nixosAfter.config.dynamicism.for.${name}.activate}
+      '';
+
+      runForChanged = submodulesChanged
+      |> lib.mapAttrsToList (name: _: runForSubmodCalled name)
       |> lib.concatStringsSep "\n";
 
     in pkgs.writeShellApplication {
       name = "dynamicism-activate";
-      text = runAllActivationScripts;
+      text = runForChanged;
       passthru.configuration = nixosAfter;
     };