Alternate implementation

Author: dra27

src/core/opamCompat.ml

@@ -130,3 +130,15 @@ module Stdlib = Pervasives
 #else
 module Stdlib = Stdlib
 #endif
+
+module Lazy =
+#if OCAML_VERSION >= (4, 13, 0)
+  Lazy
+#else
+struct
+  include Lazy
+
+  let map f x =
+    lazy (f (force x))
+end
+#endif

src/core/opamCompat.mli

@@ -97,3 +97,14 @@ module Stdlib = Pervasives
 #else
 module Stdlib = Stdlib
 #endif
+
+module Lazy
+#if OCAML_VERSION >= (4, 13, 0)
+= Lazy
+#else
+: sig
+  include module type of struct include Lazy end
+
+  val map : ('a -> 'b) -> 'a t -> 'b t
+end
+#endif

src/state/opamSwitchState.ml

@@ -34,25 +34,28 @@ let load_switch_config ?lock_kind gt switch =
        (OpamSwitch.to_string switch);
      OpamFile.Switch_config.empty)
 
-let get_available_packages gt switch switch_config ~opams =
-  OpamPackage.Map.filter (fun package opam ->
-      OpamFilter.eval_to_bool ~default:false
-        (OpamPackageVar.resolve_switch_raw ~package gt switch switch_config)
-        (OpamFile.OPAM.available opam))
-    opams
-
-let filter_pinned_packages ~pinned ~opams =
+let filter_available_packages gt switch switch_config ~opams =
+  OpamPackage.keys @@
+    OpamPackage.Map.filter (fun package opam ->
+        OpamFilter.eval_to_bool ~default:false
+          (OpamPackageVar.resolve_switch_raw ~package gt switch switch_config)
+          (OpamFile.OPAM.available opam))
+      opams
+
+let compute_available_and_pinned_packages gt switch switch_config ~pinned ~opams =
   (* remove all versions of pinned packages, but the pinned-to version *)
   let pinned_names = OpamPackage.names_of_packages pinned in
-  OpamPackage.Map.filter
-    (fun nv _ ->
-       not (OpamPackage.Name.Set.mem nv.name pinned_names) ||
-       OpamPackage.Set.mem nv pinned)
-    opams
+  let (opams, pinned) =
+    OpamPackage.Map.partition
+      (fun nv _ ->
+         not (OpamPackage.Name.Set.mem nv.name pinned_names) ||
+         OpamPackage.Set.mem nv pinned)
+      opams
+  in
+  (filter_available_packages gt switch switch_config ~opams, pinned)
 
 let compute_available_packages gt switch switch_config ~pinned ~opams =
-  let opams = filter_pinned_packages ~pinned ~opams in
-  OpamPackage.keys @@ get_available_packages gt switch switch_config ~opams
+  fst @@ compute_available_and_pinned_packages gt switch switch_config ~pinned ~opams
 
 let repos_list_raw rt switch_config =
   let global, repos =
@@ -116,7 +119,7 @@ let infer_switch_invariant_raw
             deps dmap
         in
         dmap)
-      (OpamPackage.packages_of_names (Lazy.force available_packages) @@
+      (OpamPackage.packages_of_names available_packages @@
        OpamPackage.names_of_packages @@
        compiler)
       OpamPackage.Map.empty
@@ -134,7 +137,7 @@ let infer_switch_invariant_raw
   match List.sort (fun (_, c1) (_, c2) -> compare c1 c2) counts with
   | (nv, _) :: _ ->
     let versions =
-      OpamPackage.packages_of_name (Lazy.force available_packages) nv.name
+      OpamPackage.packages_of_name available_packages nv.name
     in
     let n = OpamPackage.Set.cardinal versions in
     if n <= 1 then
@@ -154,9 +157,10 @@ let infer_switch_invariant st =
         st.installed
     else st.compiler_packages
   in
+  let lazy available_packages = st.available_packages in
   infer_switch_invariant_raw
     st.switch_global st.switch st.switch_config st.opams
-    st.packages compiler_packages st.installed_roots st.available_packages
+    st.packages compiler_packages st.installed_roots available_packages
 
 let depexts_raw ~env nv opams =
   try
@@ -331,7 +335,8 @@ let load lock_kind gt rt switch =
     OpamPackage.Map.union (fun _ x -> x) repos_package_index pinned_opams
   in
   let available_packages =
-    lazy (get_available_packages gt switch switch_config ~opams)
+    lazy (compute_available_and_pinned_packages gt switch switch_config
+            ~pinned ~opams)
   in
   let opams =
     (* Keep definitions of installed packages, but lowest priority, and after
@@ -402,8 +407,10 @@ let load lock_kind gt rt switch =
     match switch_config.invariant with
     | Some invariant -> switch_config, invariant
     | None ->
-      let available_packages = lazy (
-        OpamPackage.keys (Lazy.force available_packages))
+      let available_packages =
+        let lazy (available_packages, pinned) = available_packages in
+        OpamPackage.Set.union available_packages @@
+          filter_available_packages gt switch switch_config ~opams:pinned
       in
       let invariant =
         infer_switch_invariant_raw
@@ -430,12 +437,6 @@ let load lock_kind gt rt switch =
           switch_config;
       switch_config, invariant
   in
-  let available_packages = lazy (
-    let available_without_pinned_alternates =
-      filter_pinned_packages ~pinned ~opams:(Lazy.force available_packages)
-    in
-    OpamPackage.keys available_without_pinned_alternates)
-  in
   let conf_files =
     let conf_files =
       OpamFilename.files (OpamPath.Switch.config_dir gt.root switch)
@@ -508,6 +509,7 @@ let load lock_kind gt rt switch =
       OpamPackage.Set.empty
   ) in
   (* depext check *)
+  let available_packages = OpamCompat.Lazy.map fst available_packages in
   let sys_packages =
     if not (OpamFile.Config.depext gt.config)
     || OpamStateConfig.(!r.no_depexts) then