Add cache stats to telemetry output

src/frontend/ocamlmerlin/new/new_merlin.ml

@@ -130,11 +130,16 @@ let run = function
           let notify { Logger.section; msg } =
             `String (Printf.sprintf "%s: %s" section msg)
           in
+          let cache = Mpipeline.cache_information pipeline in
+          let format_cache (k,v) =
+            let fmt_str (k, v) = (k, `String v) in
+            (k, `Assoc (List.map fmt_str v)) in
           let format_timing (k,v) = (k, `Int (int_of_float (0.5 +. v))) in
           `Assoc [
             "class", `String class_; "value", message;
             "notifications", `List (List.rev_map notify !notifications);
-            "timing", `Assoc (List.map format_timing timing)
+            "timing", `Assoc (List.map format_timing timing);
+            "cache", `Assoc (List.map format_cache cache)
           ]
         in
         log ~title:"run(result)" "%a" Logger.json (fun () -> json);