add support for ambient-context

optional library to provide ambient-context implem using
Moonpool.Task_local_storage

.github/workflows/main.yml

@@ -27,7 +27,7 @@ jobs:
       - run: opam exec -- dune build @install
 
       # install some depopts
-      - run: opam install thread-local-storage trace hmap
+      - run: opam install thread-local-storage trace hmap ambient-context.0.2
       - run: opam exec -- dune build --profile=release --force @install @runtest
 
   compat:

dune-project

@@ -60,6 +60,7 @@
     :with-test)))
  (depopts
   hmap
+  (ambient-context (>= 0.2))
   (trace
    (>= 0.6)))
  (tags

moonpool.opam

@@ -24,6 +24,7 @@ depends: [
 ]
 depopts: [
   "hmap"
+  "ambient-context" {>= "0.2"}
   "trace" {>= "0.6"}
 ]
 build: [

src/ambient-context/dune

@@ -0,0 +1,5 @@
+(library
+ (name moonpool_ambient_context)
+ (public_name moonpool.ambient-context)
+ (optional) ; ambient-context
+ (libraries moonpool hmap ambient-context))

src/ambient-context/moonpool_ambient_context.ml

@@ -0,0 +1,21 @@
+open struct
+  module TLS = Moonpool.Task_local_storage
+end
+
+let storage : Ambient_context.Storage.t =
+  {
+    name = "moonpool";
+    get_context = TLS.get_local_hmap;
+    with_context =
+      (fun new_hmap f ->
+        let old = TLS.get_local_hmap () in
+        TLS.set_local_hmap new_hmap;
+        match f () with
+        | x ->
+          TLS.set_local_hmap old;
+          x
+        | exception exn ->
+          let bt = Printexc.get_raw_backtrace () in
+          TLS.set_local_hmap old;
+          Printexc.raise_with_backtrace exn bt);
+  }