Add mergeStringOption and factor mergeSomethingOption by introducing mergeTypedOption.

svn path=/nixpkgs/trunk/; revision=13310

1 files changed, 13 insertions, 8 deletions

diff --git a/pkgs/lib/default.nix b/pkgs/lib/default.nix
index fa71e02c01ce..e5247c57267b 100644
--- a/pkgs/lib/default.nix
+++ b/pkgs/lib/default.nix
@@ -391,14 +391,19 @@ rec {
     else if all __isAttrs list then mergeAttrs list
     else abort "${name}: Cannot merge values.";
 
-  mergeEnableOption = name: list:
-    if all (x: true == x || false == x) list
-    then fold logicalOR false list
-    else abort "${name}: Expect a boolean value.";
-
-  mergeListOption = name: list:
-    if all __isList list then concatLists list
-    else abort "${name}: Expect a list.";
+  mergeTypedOption = typeName: predicate: merge: name: list:
+    if all predicate list then merge list
+    else abort "${name}: Expect a ${typeName}.";
+
+  mergeEnableOption = mergeTypedOption "boolean"
+    (x: true == x || false == x) (fold logicalOR false);
+
+  mergeListOption = mergeTypedOption "list"
+    __isList concatLists;
+
+  mergeStringOption = mergeTypedOption "string"
+    (x: if builtins ? isString then builtins.isString x else x + "")
+    concatStrings;
 
   # Merge sets of options and bindings.
   # noOption: function to call if no option is declared.