lib: Add composeManyExtensions

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/tests/misc.nix b/lib/tests/misc.nix
index 6175f15819a7..35a5801c724f 100644
--- a/lib/tests/misc.nix
+++ b/lib/tests/misc.nix
@@ -87,6 +87,26 @@ runTests {
     expected = true;
   };
 
+  testComposeManyExtensions0 = {
+    expr = let obj = makeExtensible (self: { foo = true; });
+               emptyComposition = composeManyExtensions [];
+               composed = obj.extend emptyComposition;
+           in composed.foo;
+    expected = true;
+  };
+
+  testComposeManyExtensions =
+    let f = self: super: { bar = false; baz = true; };
+        g = self: super: { bar = super.baz or false; };
+        h = self: super: { qux = super.bar or false; };
+        obj = makeExtensible (self: { foo = self.qux; });
+    in {
+    expr = let composition = composeManyExtensions [f g h];
+               composed = obj.extend composition;
+           in composed.foo;
+    expected = (obj.extend (composeExtensions f (composeExtensions g h))).foo;
+  };
+
   testBitAnd = {
     expr = (bitAnd 3 10);
     expected = 2;