Auto call generic

default.nix

@@ -10,13 +10,38 @@ let
     rev = "c19c816e39d14a60dd368d601aa9b389b09d0bbb";
   });
 
+  inherit (lib.attrsets) mergeAttrsList mapAttrsToList;
+
+  # TODO: Move to nix-lib if generic version proposal succeeds
+  mkAutoCalledPolyPackageDir = baseDirectory:
+  let
+    namesForShard = lib.packageSets.mkNamesForDirectory baseDirectory;
+    # This is defined up here in order to allow reuse of the value (it's kind of expensive to compute)
+    # if the overlay has to be applied multiple times
+    packageFiles = mergeAttrsList (mapAttrsToList namesForShard (builtins.readDir baseDirectory));
+  in
+  # TODO: Consider optimising this using `builtins.deepSeq packageFiles`,
+  # which could free up the above thunks and reduce GC times.
+  # Currently this would be hard to measure until we have more packages
+  # and ideally https://github.com/NixOS/nix/pull/8895
+  self: super:
+    {
+      _internalCallPolyFile = file: self.callPackage (import file { inherit (self) mkGenericPkg; }) { };
+    }
+    // builtins.mapAttrs
+      (name: value: self._internalCallPolyFile value)
+      packageFiles;
+
+  polyPkgOverlay = mkAutoCalledPolyPackageDir ./polyPkgs;
+
   pkgsOverlay = lib.mkAutoCalledPackageDir ./pkgs;
 
   toplevelOverlay = import ./top-level.nix;
 in
 
 import stdenvRepo {
   overlays = [
+    polyPkgOverlay
     pkgsOverlay
     toplevelOverlay
   ];

polyPkgs/openssl/default.nix

@@ -0,0 +1,9 @@
+{ mkGenericPkg }:
+
+mkGenericPkg {
+  versions = ./versions.nix;
+  aliases = ./aliases.nix;
+  defaultSelector = (p: p.v3_3);
+  genericBuilder = ./generic.nix;
+}
+