refactor: modules/users/s6-rc.nix

modules/users/s6-rc.nix

@@ -1,73 +1,85 @@
 { lib, pkgs, ... }:
 let
   logBase = "$HOME/.local/state/s6/logs";
+  maybe = cond: value: if cond then value else null;
   normalizeName = name: lib.removeSuffix ".service" (lib.removeSuffix ".target" name);
 
-  # infers the service type from the arguments and dispatches appropriately
-  genService = { name, run, finish, depends }: let
+  # create a derivation whose output is the on-disk representation of some attrset.
+  # @path: /foo/bar/...
+  # @obj: one of:
+  #   - { file = { text = "foo bar"; executable = true|false; } }
+  #   - { dir = <obj>; }
+  fsItemToDerivation = path: obj: if obj ? dir then
+    pkgs.symlinkJoin {
+      name = "s6-${path}";
+      paths = lib.mapAttrsToList
+        (n: v: fsItemToDerivation "${path}/${n}" v)
+        obj.dir
+      ;
+    }
+  else if obj ? text then
+    if obj.text != null then
+      pkgs.writeTextFile {
+        name = "s6-${path}";
+        destination = path;
+        text = obj.text;
+      }
+    else
+      pkgs.emptyDirectory
+  else if obj ? executable then
+    if obj.executable != null then
+      pkgs.writeTextFile {
+        name = "s6-${path}";
+        destination = path;
+        executable = true;
+        text = obj.executable;
+      }
+    else
+      pkgs.emptyDirectory
+  else throw "don't know how to convert fs item at path ${path} to derivation: ${obj}";
+
+  # call with an AttrSet of fs items:
+  # example:
+  # ```
+  # fsToDerivation {
+  #   usr.dir = {
+  #     normal.text = "i'm /usr/normal";
+  #     exec.executable = ''
+  #       #!/bin/sh
+  #       echo "i'm executable"
+  #     '';
+  #     lib.dir = { ... };
+  #   };
+  #   bin.dir = { ... };
+  # }
+  fsToDerivation = fs: fsItemToDerivation "/" { dir = fs; };
+
+  # infers the service type from the arguments and creates an attrset usable by `fsToDerivation`.
+  serviceToFs = { name, run, finish, depends }: let
     name' = normalizeName name;
     type = if run != null then "longrun" else "bundle";
-  in genService' {
-    name = name';
-    inherit type;
-    # TODO: a bundle can totally have dependencies. i can't just map them *all* to contents.
-    depends = lib.optionals (type == "longrun") depends;
-    finish = finish;
-    longrun-run = run;
-    bundle-contents = lib.optionals (type == "bundle") depends;
-  };
-
-  genService' = {
-    name,
-    type,
-    depends,
-    finish,
-    longrun-run,
-    bundle-contents,
-  }: pkgs.symlinkJoin {
-    name = "s6-${name}";
-    paths = [
-      (pkgs.writeTextFile {
-        name = "s6-${name}-type";
-        destination = "/${name}/type";
-        text = type;
-      })
-    ] ++ lib.optionals (finish != null) [
-      (pkgs.writeTextFile {
-        # TODO: use 'writeShellScript'?
-        name = "s6-${name}-finish";
-        destination = "/${name}/finish";
-        executable = true;
-        text = ''
-          #!/bin/sh
-          ${finish}
-        '';
-      })
-    ] ++ lib.optionals (longrun-run != null) [
-      (pkgs.writeTextFile {
-        name = "s6-${name}-run";
-        destination = "/${name}/run";
-        executable = true;
-        # TODO: consider using `makeWrapper`/`makeBinaryWrapper`?
-        text = ''
-          #!/bin/sh
-          echo "starting: s6-${name}"
-          ${longrun-run} 2>&1
-        '';
-      })
-    ] ++ lib.optionals (bundle-contents != null) [
-      (pkgs.writeTextFile {
-        name = "s6-${name}-contents";
-        destination = "/${name}/contents";
-        text = lib.concatStringsSep "\n" (builtins.map normalizeName bundle-contents);
-      })
-    ] ++ builtins.map
-      (d: pkgs.writeTextFile {
-        name = "s6-${name}-depends-${d}";
-        destination = "/${name}/dependencies.d/${normalizeName d}";
-        text = "";
-      })
-      depends;
+  in {
+    "${name}".dir = {
+      "type".text = type;
+      "finish".executable = maybe (finish != null) ''
+        #!/bin/sh
+        ${finish}
+      '';
+      "run".executable = maybe (run != null) ''
+        #!/bin/sh
+        echo "starting: s6-${name}"
+        ${run} 2>&1
+      '';
+      "contents".text = maybe (type == "bundle") (
+        lib.concatStringsSep "\n" (builtins.map normalizeName depends)
+      );
+      # TODO: a bundle can also have dependencies
+      "dependencies.d".dir = lib.optionalAttrs (type == "longrun") (
+        lib.genAttrs
+          (builtins.map normalizeName depends)
+          (dep: { text = ""; })
+      );
+    };
   };
 
   # create a directory, containing N subdirectories:
@@ -78,10 +90,11 @@ let
   #   - type
   #   - run
   # - ...
-  genServices = svcs: pkgs.symlinkJoin {
-    name = "s6-user-services";
-    paths = builtins.map genService svcs;
-  };
+  genServices = svcs: fsToDerivation (lib.foldl'
+    (acc: srv: acc // (serviceToFs srv))
+    {}
+    svcs
+  );
 
   # output is a directory containing:
   # - db