ocamlPackages.ptime: use finalAttrs pattern

pkgs/development/ocaml-modules/ptime/default.nix

@@ -1,28 +1,40 @@
-{ stdenv, lib, fetchurl, ocaml, findlib, ocamlbuild, topkg
+{ stdenv
+, lib
+, fetchurl
+, ocaml
+, findlib
+, ocamlbuild
+, topkg
 }:
 
-lib.throwIfNot (lib.versionAtLeast ocaml.version "4.08")
-  "ptime is not available for OCaml ${ocaml.version}"
-
-stdenv.mkDerivation rec {
+stdenv.mkDerivation (finalAttrs: {
   version = "1.1.0";
   pname = "ocaml${ocaml.version}-ptime";
 
   src = fetchurl {
-    url = "https://erratique.ch/software/ptime/releases/ptime-${version}.tbz";
-    sha256 = "sha256-y/WxVFT7JxBeLDNAI+HhHY+TnXF4hw9cvo7SbfcBPrE=";
+    url = "https://erratique.ch/software/ptime/releases/ptime-${finalAttrs.version}.tbz";
+    hash = "sha256-y/WxVFT7JxBeLDNAI+HhHY+TnXF4hw9cvo7SbfcBPrE=";
   };
 
-  nativeBuildInputs = [ ocaml findlib ocamlbuild topkg ];
-  buildInputs = [ topkg ];
+  nativeBuildInputs = [
+    findlib
+    ocaml
+    ocamlbuild
+    topkg
+  ];
+
+  buildInputs = [
+    topkg
+  ];
 
   strictDeps = true;
 
   inherit (topkg) buildPhase installPhase;
 
   meta = {
-    homepage = "https://erratique.ch/software/ptime";
     description = "POSIX time for OCaml";
+    homepage = "https://erratique.ch/software/ptime";
+    license = lib.licenses.isc;
     longDescription = ''
       Ptime has platform independent POSIX time support in pure OCaml.
       It provides a type to represent a well-defined range of POSIX timestamps
@@ -35,7 +47,6 @@ stdenv.mkDerivation rec {
 
       Ptime is not a calendar library.
     '';
-    license = lib.licenses.isc;
     maintainers = with lib.maintainers; [ sternenseemann ];
   };
-}
+})

pkgs/top-level/ocaml-packages.nix

@@ -1433,7 +1433,10 @@ let
 
     psq = callPackage ../development/ocaml-modules/psq { };
 
-    ptime = callPackage ../development/ocaml-modules/ptime { };
+    ptime =
+      if lib.versionAtLeast ocaml.version "4.08"
+      then callPackage ../development/ocaml-modules/ptime { }
+      else null;
 
     ptmap = callPackage ../development/ocaml-modules/ptmap { };