Merge branch 'master' into staging-next

Quite many rebuilds from master:
> Estimating rebuild amount by counting changed Hydra jobs.
>    3926 x86_64-darwin
>    4645 x86_64-linux

lib/default.nix

@@ -66,7 +66,7 @@ let
       stringLength sub substring tail;
     inherit (trivial) id const pipe concat or and bitAnd bitOr bitXor
       bitNot boolToString mergeAttrs flip mapNullable inNixShell min max
-      importJSON warn info showWarnings nixpkgsVersion version mod compare
+      importJSON importTOML warn info showWarnings nixpkgsVersion version mod compare
       splitByAndCompare functionArgs setFunctionArgs isFunction toHexString toBaseDigits;
     inherit (fixedPoints) fix fix' converge extends composeExtensions
       makeExtensible makeExtensibleWithCustomName;

lib/modules.nix

@@ -875,4 +875,21 @@ rec {
       ];
     };
 
+  /* Use this function to import a JSON file as NixOS configuration.
+
+     importJSON -> path -> attrs
+  */
+  importJSON = file: {
+    _file = file;
+    config = lib.importJSON file;
+  };
+
+  /* Use this function to import a TOML file as NixOS configuration.
+
+     importTOML -> path -> attrs
+  */
+  importTOML = file: {
+    _file = file;
+    config = lib.importTOML file;
+  };
 }

lib/trivial.nix

@@ -281,6 +281,12 @@ rec {
   importJSON = path:
     builtins.fromJSON (builtins.readFile path);
 
+  /* Reads a TOML file.
+
+     Type :: path -> any
+  */
+  importTOML = path:
+    builtins.fromTOML (builtins.readFile path);
 
   ## Warnings