populate file: admit derivations

README.md

@@ -217,6 +217,8 @@ Supported attributes:
   whether a file has changed.  This is useful when `path` points at files
   with mangled timestamps, e.g. the Nix store.
 
+  The default value is `true` if `path` is a derivation, and `false` otherwise.
+
 * `filters` (optional)
   List of filters that should be passed to [`rsync`](https://rsync.samba.org/).
   Filters are specified as attribute sets with the attributes `type` and

ci.nix

@@ -5,7 +5,7 @@ let
   pkgs = import "${krops}/pkgs" {};
 
   source = lib.evalSource [{
-    nixos-config.file = toString (pkgs.writeText "nixos-config" ''
+    nixos-config.file = pkgs.writeText "nixos-config" ''
       { pkgs, ... }: {
 
         fileSystems."/" = { device = "/dev/sda1"; };
@@ -13,7 +13,7 @@ let
         services.openssh.enable = true;
         environment.systemPackages = [ pkgs.git ];
       }
-    '');
+    '';
     nixpkgs.symlink = toString <nixpkgs>;
   }];
 in {

lib/types/populate.nix

@@ -21,11 +21,15 @@
       };
       file = lib.mkOption {
         apply = x:
-          if lib.types.absolute-pathname.check x
+          if lib.types.absolute-pathname.check x || lib.types.package.check x
             then { path = x; }
             else x;
         default = null;
-        type = lib.types.nullOr (lib.types.either lib.types.absolute-pathname source-types.file);
+        type = lib.types.nullOr (lib.types.oneOf [
+          lib.types.absolute-pathname
+          lib.types.package
+          source-types.file
+        ]);
       };
       git = lib.mkOption {
         default = null;

pkgs/populate/default.nix

@@ -45,10 +45,21 @@ let
   '';
 
   pop.file = target: source: let
-    config = rsyncDefaultConfig // sourceConfig;
-    sourceConfig = getAttrs (attrNames rsyncDefaultConfig) source;
+    config = rsyncDefaultConfig // derivedConfig // sourceConfig;
+    derivedConfig = {
+      useChecksum =
+        if isDerivation source.path
+          then true
+          else rsyncDefaultConfig.useChecksum;
+    };
+    sourceConfig =
+      filterAttrs (name: _: elem name (attrNames rsyncDefaultConfig)) source;
+    sourcePath =
+      if isDerivation source.path
+        then quote (toString source.path)
+        else quote source.path;
   in
-    rsync' target config (quote source.path);
+    rsync' target config sourcePath;
 
   pop.git = target: source: runShell target /* sh */ ''
     set -efu
@@ -198,7 +209,7 @@ let
     useChecksum = false;
     exclude = [];
     filters = [];
-    deleteExcluded = true
+    deleteExcluded = true;
   };
 
   runShell = target: command: