feat log: add Log_ctx.set_tag

src/log/log_ctx.ml

@@ -17,6 +17,17 @@ let get_tags_from_ctx () : Logs.Tag.set =
     (fun _ (Logs.Tag.V (tag, v)) set -> Logs.Tag.add tag v set)
     map Logs.Tag.empty
 
+let set_tag (tag : _ tag) v : unit =
+  match
+    LS.get_in_local_hmap_opt ctx_k |> Option.value ~default:Str_map.empty
+  with
+  | exception _ -> ()
+  | old_map ->
+    let new_map =
+      Str_map.add (Logs.Tag.name tag) (Logs.Tag.V (tag, v)) old_map
+    in
+    LS.set_in_local_hmap ctx_k new_map
+
 let with_tag (tag : _ tag) v (f : unit -> 'b) : 'b =
   match
     LS.get_in_local_hmap_opt ctx_k |> Option.value ~default:Str_map.empty

src/log/log_ctx.mli

@@ -8,6 +8,9 @@ type 'a tag = 'a Logs.Tag.def
 
 val create_tag : ?doc:string -> string -> 'a Fmt.printer -> 'a tag
 
+val set_tag : 'a tag -> 'a -> unit
+(** Set tag for the rest of the current task, does nothing outside of a task *)
+
 val with_tag : 'a tag -> 'a -> (unit -> 'b) -> 'b
 (** Set the tag to this value locally in the ambient context *)