2 files changed, 7 insertions, 0 deletions
diff --git a/lib/future.ml b/lib/future.ml
index 1e9cada513..d8f7b3a947 100644
--- a/lib/future.ml
+++ b/lib/future.ml
@@ -111,6 +111,11 @@ let purify f x =
     v
   with e -> let e = Errors.push e in !unfreeze state; raise e
 
+let transactify f x =
+  let state = !freeze () in
+  try f x
+  with e -> let e = Errors.push e in !unfreeze state; raise e
+
 let purify_future f x =
   match !x with
   | Val _ | Exn _ | Delegated | Dropped -> f x
diff --git a/lib/future.mli b/lib/future.mli
index 39be0c1806..f07d325e03 100644
--- a/lib/future.mli
+++ b/lib/future.mli
@@ -59,4 +59,6 @@ val set_freeze : (unit -> Dyn.t) -> (Dyn.t -> unit) -> unit
 
 (* Once set_freeze is called we can purify a computation *)
 val purify : ('a -> 'b) -> 'a -> 'b
+(* And also let a function alter the state but backtrack if it raises exn *)
+val transactify : ('a -> 'b) -> 'a -> 'b