lib.gvariant: escape backslashes in strings

PR #1433

modules/lib/gvariant.nix

@@ -123,7 +123,7 @@ in rec {
 
   mkString = v:
     mkPrimitive type.string v // {
-      __toString = self: "'${escape [ "'" ] self.value}'";
+      __toString = self: "'${escape [ "'" "\\" ] self.value}'";
     };
 
   mkObjectpath = v:

tests/lib/types/gvariant-merge.nix

@@ -26,6 +26,7 @@ in {
 
         { string = "foo"; }
         { string = "foo"; }
+        { escapedString = "' \\"; }
 
         { tuple = mkTuple [ 1 [ "foo" ] ]; }
 
@@ -46,6 +47,7 @@ in {
             bool = true
             emptyArray1 = @as []
             emptyArray2 = @as []
+            escapedString = '\' \\'
             float = 3.140000
             int = 42
             list = @as ['one','two']