Use polymorphic variants for chunk key encoding separator.

lib/extensions.ml

@@ -47,17 +47,15 @@ module RegularGrid = struct
       Ok y.configuration.chunk_shape
 end
 
-type separator = Dot | Slash
-
 module ChunkKeyEncoding = struct
   type encoding = Default | V2
   type config = {separator : string} [@@deriving yojson]
   type key_encoding = config Util.ExtPoint.t [@@deriving yojson]
   type t = {encoding : encoding; sep : string}
 
   let create = function
-    | Dot -> {encoding = Default; sep = "."}
-    | Slash -> {encoding = Default; sep = "/"}
+    | `Dot -> {encoding = Default; sep = "."}
+    | `Slash -> {encoding = Default; sep = "/"}
 
   (* map a chunk coordinate index to a key. E.g, (2,3,1) maps to c/2/3/1 *)
   let encode t index =

lib/extensions.mli

@@ -10,14 +10,9 @@ module RegularGrid : sig
   val to_yojson : t -> Yojson.Safe.t
 end
 
-type separator = Dot | Slash
-(** A type representing the separator in an array chunk's key encoding.
-    For example, [Dot] is "/", and is used to encode the chunk index
-    [(0, 3, 5)] as [0/3/5]. *) 
-
 module ChunkKeyEncoding : sig
   type t
-  val create : separator -> t
+  val create : [< `Slash | `Dot > `Slash ] -> t
   val encode : t -> int array -> string
   val equal : t -> t -> bool
   val of_yojson : Yojson.Safe.t -> (t, string) result

lib/metadata.ml

@@ -117,7 +117,7 @@ module ArrayMetadata = struct
   [@@deriving yojson, eq]
 
   let create
-    ?(sep=Extensions.Slash)
+    ?(sep=`Slash)
     ?(codecs=Codecs.Chain.default)
     ?(dimension_names=[])
     ?(attributes=`Null)

lib/metadata.mli

@@ -34,7 +34,7 @@ module ArrayMetadata : sig
   (** A type representing a parsed array metadata document. *)
 
   val create :
-    ?sep:Extensions.separator ->
+    ?sep:[< `Dot | `Slash > `Slash ] ->
     ?codecs:Codecs.Chain.t ->
     ?dimension_names:string option list ->
     ?attributes:Yojson.Safe.t ->

lib/storage/storage.ml

@@ -27,7 +27,7 @@ module Make (M : STORE) : S with type t = M.t = struct
     | Some n -> create_group t n
 
   let create_array
-    ?(sep=Extensions.Slash)
+    ?(sep=`Slash)
     ?(dimension_names=[])
     ?(attributes=`Null)
     ?codecs

lib/storage/storage_intf.ml

@@ -54,7 +54,7 @@ module type S = sig
       is already a member of this store. *)
 
   val create_array
-    : ?sep:Extensions.separator ->
+    : ?sep:[< `Dot | `Slash > `Slash ] ->
       ?dimension_names:string option list ->
       ?attributes:Yojson.Safe.t ->
       ?codecs:Codecs.chain ->