lib/generators.toPretty: Only quote attribute names if necessary

lib/generators.nix

@@ -227,7 +227,7 @@ rec {
       else "{ "
           + libStr.concatStringsSep " " (libAttr.mapAttrsToList
               (name: value:
-                "${toPretty args name} = ${toPretty args value};") v)
+                "${libStr.escapeNixIdentifier name} = ${toPretty args value};") v)
         + " }"
     else if isFunction v then
       let fna = lib.functionArgs v;

lib/tests/misc.nix

@@ -469,7 +469,7 @@ runTests {
       function = "<λ>";
       functionArgs = "<λ:{(arg),foo}>";
       list = "[ 3 4 ${function} [ false ] ]";
-      attrs = "{ \"foo\" = null; \"foo bar\" = \"baz\"; }";
+      attrs = "{ foo = null; \"foo bar\" = \"baz\"; }";
       drv = "<δ:test>";
     };
   };