Configurable cache period

src/frontend/ocamlmerlin/new/new_merlin.ml

@@ -91,8 +91,11 @@ let run = function
         (* Start processing query *)
         Logger.with_log_file Mconfig.(config.merlin.log_file)
           ~sections:Mconfig.(config.merlin.log_sections) @@ fun () ->
+        let cache_period = match Lib_config.cache_period () with
+          | Some p -> p
+          | None -> Mconfig.(config.merlin.cache_period) in
         Mocaml.flush_caches
-          ~older_than:(float_of_int (60 * Mconfig.(config.merlin.cache_period))) ();
+          ~older_than:(float_of_int (60 * cache_period)) ();
         File_id.with_cache @@ fun () ->
         let source = Msource.make (Misc.string_of_file stdin) in
         let pipeline = Mpipeline.make config source in

src/utils/lib_config.ml

@@ -4,6 +4,13 @@ let set_program_name name = program_name := name
 
 let program_name () = !program_name
 
+
+let cache_period = ref None
+
+let set_cache_period period = cache_period := Some period
+
+let cache_period () = !cache_period
+
 module Json = struct
   let set_pretty_to_string f =
     Std.Json.pretty_to_string := f

src/utils/lib_config.mli

@@ -9,6 +9,12 @@ val set_program_name : string -> unit
     [set_program]. Defaults to "Merlin". *)
 val program_name : unit -> string
 
+(** [set_cache_period] sets the file cache retention period. Measured in minutes. *)
+val set_cache_period : int -> unit
+
+(** [program ()] returns file cache retention period. Defaults to None. *)
+val cache_period : unit -> int option
+
 module Json : sig
     (** Merlin's logger requires a Json pretty-printer for correct operation.
         [set_pretty_to_string] can be used to provide one. A common pretifier