lib/types: Add oneOf, extension of either to a list of types

lib/tests/modules.sh

@@ -71,6 +71,15 @@ checkConfigError 'The option value .* in .* is not of type.*positive integer.*'
 checkConfigOutput "42" config.value ./declare-int-between-value.nix ./define-value-int-positive.nix
 checkConfigError 'The option value .* in .* is not of type.*between.*-21 and 43.*inclusive.*' config.value ./declare-int-between-value.nix ./define-value-int-negative.nix
 
+# Check either types
+# types.either
+checkConfigOutput "42" config.value ./declare-either.nix ./define-value-int-positive.nix
+checkConfigOutput "\"24\"" config.value ./declare-either.nix ./define-value-string.nix
+# types.oneOf
+checkConfigOutput "42" config.value ./declare-oneOf.nix ./define-value-int-positive.nix
+checkConfigOutput "[ ]" config.value ./declare-oneOf.nix ./define-value-list.nix
+checkConfigOutput "\"24\"" config.value ./declare-oneOf.nix ./define-value-string.nix
+
 # Check mkForce without submodules.
 set -- config.enable ./declare-enable.nix ./define-enable.nix
 checkConfigOutput "true" "$@"

lib/tests/modules/declare-either.nix

@@ -0,0 +1,5 @@
+{ lib, ... }: {
+  options.value = lib.mkOption {
+    type = lib.types.either lib.types.int lib.types.str;
+  };
+}

lib/tests/modules/declare-oneOf.nix

@@ -0,0 +1,9 @@
+{ lib, ... }: {
+  options.value = lib.mkOption {
+    type = lib.types.oneOf [
+      lib.types.int
+      (lib.types.listOf lib.types.int)
+      lib.types.str
+    ];
+  };
+}

lib/types.nix

@@ -443,6 +443,13 @@ rec {
       functor = (defaultFunctor name) // { wrapped = [ t1 t2 ]; };
     };
 
+    # Any of the types in the given list
+    oneOf = ts:
+      let
+        head' = if ts == [] then throw "types.oneOf needs to get at least one type in its argument" else head ts;
+        tail' = tail ts;
+      in foldl' either head' tail';
+
     # Either value of type `finalType` or `coercedType`, the latter is
     # converted to `finalType` using `coerceFunc`.
     coercedTo = coercedType: coerceFunc: finalType: