From 6ccf554645bda0577c44a0a1970e754b3fe982e5 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Thu, 4 Dec 2025 00:24:42 -0500
Subject: [PATCH] feat span: ambient span

---
 src/core/span.ml   | 10 ++++++++++
 src/core/span.mli  |  7 +++++++
 src/core/tracer.ml | 12 ++----------
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/src/core/span.ml b/src/core/span.ml
index f0135b40..5b771d58 100644
--- a/src/core/span.ml
+++ b/src/core/span.ml
@@ -121,3 +121,13 @@ let add_links' (self : t) (links : unit -> Span_link.t list) : unit =
 let set_status = span_set_status
 
 let set_kind = span_set_kind
+
+let k_context : t Context.key = Context.new_key ()
+
+(** Find current span from ambient-context *)
+let get_ambient () : t option = Ambient_context.get k_context
+
+(** [with_ambient span f] runs [f()] with the current ambient span being set to
+    [span] *)
+let[@inline] with_ambient (span : t) (f : unit -> 'a) : 'a =
+  Ambient_context.with_key_bound_to k_context span (fun _ -> f ())
diff --git a/src/core/span.mli b/src/core/span.mli
index 673654a9..3fcaf541 100644
--- a/src/core/span.mli
+++ b/src/core/span.mli
@@ -105,3 +105,10 @@ val set_status : t -> Span_status.t -> unit
 val set_kind : t -> Span_kind.t -> unit
 (** Set the span's kind.
     @since 0.11 *)
+
+val get_ambient : unit -> t option
+(** Find current span from ambient-context *)
+
+val with_ambient : t -> (unit -> 'a) -> 'a
+(** [with_ambient span f] runs [f()] with the current ambient span being set to
+    [span] *)
diff --git a/src/core/tracer.ml b/src/core/tracer.ml
index f15c6985..b0dfbc2a 100644
--- a/src/core/tracer.ml
+++ b/src/core/tracer.ml
@@ -55,17 +55,9 @@ let (emit [@deprecated "use an explicit tracer"]) =
   | None -> ()
   | Some exp -> exp#send_trace spans
 
-(* TODO: remove scope, use span directly *)
-type scope = Scope.t = {
-  trace_id: Trace_id.t;
-  span_id: Span_id.t;
-  mutable items: Scope.item_list;
-}
-[@@deprecated "use Scope.t"]
+let (add_event [@deprecated "use Span.add_event"]) = Span.add_event
 
-let (add_event [@deprecated "use Scope.add_event"]) = Scope.add_event
-
-let (add_attrs [@deprecated "use Scope.add_attrs"]) = Scope.add_attrs
+let (add_attrs [@deprecated "use Span.add_attrs"]) = Span.add_attrs
 
 let with_' ?(tracer = simple_main_exporter) ?(force_new_trace_id = false)
     ?trace_state ?(attrs : (string * [< Value.t ]) list = []) ?kind ?trace_id