From 1b5e4128c7266d1c534aeafe25278b054604d826 Mon Sep 17 00:00:00 2001
From: Jon Ludlam <jonathan.ludlam@citrix.com>
Date: Wed, 23 Nov 2016 10:46:22 +0000
Subject: [PATCH] Add a functor to help define errors

Signed-off-by: Jon Ludlam <jonathan.ludlam@citrix.com>
---
 example/example3_idl.ml |  8 ++------
 lib/idl.ml              | 10 ++++++++++
 lib/idl.mli             |  4 ++++
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/example/example3_idl.ml b/example/example3_idl.ml
index 491c46a4..30b04f9e 100644
--- a/example/example3_idl.ml
+++ b/example/example3_idl.ml
@@ -36,13 +36,9 @@ type blocklist = {
 type error =
   | Unimplemented of string
   [@@deriving rpcty]
-exception Exn of error
 
-let error = Idl.Error.{
-    def=error;
-    raiser=(fun e -> raise (Exn e));
-    matcher=(function | Exn e -> Some e | _ -> None);
-  }
+module E = Idl.Error.Make(struct type t=error let t = error end)
+let error = E.error
 
 type domain = string
   [@@deriving rpcty]
diff --git a/lib/idl.ml b/lib/idl.ml
index a28b60ec..165fa256 100644
--- a/lib/idl.ml
+++ b/lib/idl.ml
@@ -22,6 +22,16 @@ module Error = struct
     raiser : 'a -> exn;
     matcher : exn -> 'a option;
   }
+
+  module Make(T : sig type t val t : t Rpc.Types.def end) = struct
+    exception Exn of T.t
+    let error = {
+        def = T.t;
+        raiser = (function e -> Exn e);
+        matcher = (function | Exn e -> Some e | _ -> None)
+      }
+  end
+
 end
 
 module Interface = struct
diff --git a/lib/idl.mli b/lib/idl.mli
index 07da30bf..9aa84343 100644
--- a/lib/idl.mli
+++ b/lib/idl.mli
@@ -29,6 +29,10 @@ module Error : sig
     raiser : 'a -> exn;
     matcher : exn -> 'a option;
   }
+
+  module Make(T : sig type t val t : t Rpc.Types.def end) : sig
+    val error : T.t t
+  end
 end
 
 (** An interface is a collection of RPC declarations. *)