Add option type "str" for unique strings

An annoying and dangerous property of "types.string" is that it merges
multiple definitions by concatenating them, which almost never
produces a sensible result.  (Those options for which it does make
sense typically should use "types.lines" instead, and things only work
because the option definitions already end in a newline.)  Of course,
you can use "types.uniq types.string", but that's rather verbose, and
inconsistent with other basic types like "types.int".

Changing the behaviour of "types.string" to be unique by default is
not an option, given the large number of options that use it.  So
instead, we now have "types.str", which is equivalent to "types.uniq
types.string".

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/types.nix b/lib/types.nix
index 34d06a9144fe..8deb379c25a9 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -54,6 +54,14 @@ rec {
       check = builtins.isInt;
     };
 
+    str = mkOptionType {
+      name = "string";
+      check = builtins.isString;
+      merge = mergeOneOption;
+    };
+
+    # Deprecated; should not be used because it quietly concatenates
+    # strings, which is usually not what you want.
     string = mkOptionType {
       name = "string";
       check = builtins.isString;