Use an explicit cache to avoid using the global cache

cli/lock.ml

@@ -224,36 +224,36 @@ let interpret_solver_error ~repositories solver = function
 
 (** Turns each repository URL into a path to the repository's sources,
     eventually fetching them from the remote. *)
-let make_repository_locally_available global_state url =
+let make_repository_locally_available url =
   let open OpamProcess.Job.Op in
   match OpamUrl.local_dir url with
   | Some path when Opam.Url.is_local_filesystem url ->
       Done (Ok (OpamFilename.Dir.to_string OpamFilename.Op.(path / "packages")))
   | _ -> (
+      let tmp_dir = Fpath.(Bos.OS.Dir.default_tmp () / "opam-monorepo") in
       (* the URL might contain all kind of invalid characters like slashes -> hash *)
       let repo_dir =
         url |> OpamUrl.to_string |> Digest.string |> Digest.to_hex
       in
-      let dir =
-        Fpath.(Bos.OS.Dir.default_tmp () / "opam-monorepo" / "repos" / repo_dir)
-      in
+      let dir = Fpath.(tmp_dir / "repos" / repo_dir) in
+      let cache_dir = Fpath.(tmp_dir / "cache") in
       let url =
         match OpamUrl.backend_of_string url.transport with
         | `http -> OpamUrl.Op.(url / "index.tar.gz")
         | `rsync | #OpamUrl.version_control -> url
       in
-      match Bos.OS.Dir.create dir with
+      match Result.List.map ~f:Bos.OS.Dir.create [ cache_dir; dir ] with
       | Error (`Msg msg) -> Done (Rresult.R.error_msg msg)
       | Ok _ -> (
-          Opam.pull_tree ~url ~hashes:[] ~dir global_state @@| function
+          Opam.pull_tree_with_cache ~cache_dir ~url ~hashes:[] ~dir @@| function
           | Error (`Msg msg) -> Rresult.R.error_msg msg
           | Ok () ->
               let packages = Fpath.(dir / "packages" |> to_string) in
               Ok packages))
 
-let make_repositories_locally_available global_state repositories =
+let make_repositories_locally_available repositories =
   repositories
-  |> OpamProcess.Job.seq_map (make_repository_locally_available global_state)
+  |> OpamProcess.Job.seq_map make_repository_locally_available
   |> OpamProcess.Job.run |> Result.List.all
 
 let opam_env_from_global_state global_state =
@@ -289,7 +289,7 @@ let calculate_opam ~source_config ~build_only ~allow_jbuilder
                 Fmt.(list ~sep:(const char '\n') Opam.Pp.url)
                 repositories);
           let* local_repo_dirs =
-            make_repositories_locally_available global_state repositories
+            make_repositories_locally_available repositories
           in
           let opam_env = extract_opam_env ~source_config global_state in
           let solver = Opam_solve.explicit_repos_solver in

lib/opam.ml

@@ -56,11 +56,8 @@ let has_cross_compile_tag opam =
   let tags = OpamFile.OPAM.tags opam in
   List.mem ~set:tags "cross-compile"
 
-let pull_tree ~url ~hashes ~dir global_state =
+let pull_tree_with_cache' ~cache_dir ~url ~hashes ~dir =
   let dir_str = Fpath.to_string dir in
-  let cache_dir =
-    OpamRepositoryPath.download_cache global_state.OpamStateTypes.root
-  in
   let label = dir_str in
   (* Opam requires a label for the pull, it's only used for logging *)
   let opam_dir = OpamFilename.Dir.of_string dir_str in
@@ -70,6 +67,16 @@ let pull_tree ~url ~hashes ~dir global_state =
   | Not_available (_, long_msg) ->
       Error (`Msg (Printf.sprintf "Failed to pull %s: %s" label long_msg))
 
+let pull_tree ~url ~hashes ~dir global_state =
+  let cache_dir =
+    OpamRepositoryPath.download_cache global_state.OpamStateTypes.root
+  in
+  pull_tree_with_cache' ~cache_dir ~url ~hashes ~dir
+
+let pull_tree_with_cache ~cache_dir =
+  let cache_dir = cache_dir |> Fpath.to_string |> OpamFilename.Dir.of_string in
+  pull_tree_with_cache' ~cache_dir
+
 module Url = struct
   type t = Git of { repo : string; ref : string option } | Other of string
 

lib/opam.mli

@@ -170,6 +170,16 @@ val pull_tree :
     if sucessful and an error otherwise.
     This benefits from opam's global cache.*)
 
+val pull_tree_with_cache :
+  cache_dir:Fpath.t ->
+  url:OpamUrl.t ->
+  hashes:OpamHash.t list ->
+  dir:Fpath.t ->
+  (unit, [> `Msg of string ]) result OpamProcess.job
+(** Pulls the sources from [url] to [dir] using opam's library. Returns the target directory path
+    if sucessful and an error otherwise.
+    Uses a dedicated path for caching. *)
+
 val local_package_version :
   OpamFile.OPAM.t ->
   explicit_version:OpamTypes.version option ->