clean up

Author: bobzhang

jscomp/core/destruct_exn.md

@@ -0,0 +1,39 @@
+
+
+
+Its essential is 
+
+```ocaml
+external destruct : 'b -> (exn -> 'a) 
+```
+
+However it does not prevent things like 
+
+```ocaml
+destruct v begin fun exn -> 
+   Js.log exn ; 
+   match exn with 
+   | .. 
+   | .. 
+```
+
+Here it forces us to answer whether `v` is exception or not, 
+
+while such syntax below does not need us answer `v` is exception 
+or not,  it just asks us to answer it matches a branch of exception or not which can be done in a sound way.
+
+```ocaml
+match%exn v with 
+| .. 
+| .. 
+```
+
+However, we need make sure such cases not happen
+
+```ocaml
+match%exn v with 
+| e -> ...
+
+```
+Or any vagous pattern which needs us to answer if 
+it is an exception or not

jscomp/runtime/caml_exceptions.ml

@@ -63,10 +63,44 @@ let create (str : string) : Caml_builtin_exceptions.exception_block =
   v 
 
 external isUndefined : 'a -> bool = "#is_undef"
-(** It could be either customized exception or built in exception *)
-let isCamlException e = 
+
+
+(**
+  This function should never throw
+  It could be either customized exception or built in exception 
+  Note due to that in OCaml extensible variants have the same 
+  runtime representation as exception, so we can not 
+  really tell the difference. 
+  
+  However, if we make a false alarm, classified extensible variant 
+  as exception, it will be OKAY for nested pattern match
+
+   {[
+     match toExn x : exn option with 
+     | Some _ 
+       -> Js.log "Could be an OCaml exception or an open variant"
+          (* If it is an Open variant, it will never pattern match, 
+             This is Okay, since exception could never have exhaustive pattern match
+             
+          *)
+     | None -> Js.log "Not an OCaml exception for sure"
+   ]}
+
+   However, there is still something wrong, since if user write such code
+   {[
+     match toExn x with 
+     | Some _ -> (* assert it is indeed an exception *)
+       (* This assertion is wrong, since it could be an open variant *)
+     | None -> (* assert it is not an exception *)
+   ]}
+
+   This is not a problem in `try .. with` since the logic above is not expressible, see more design in [destruct_exn.md]
+  *)
+let isCamlExceptionOrOpenVariant e = 
   Obj.tag e = object_tag  (* nullary exception *)
   ||
   let slot = Obj.field e 0 in 
   not (isUndefined slot) &&
   (Obj.tag slot = object_tag)
+
+

jscomp/runtime/caml_exceptions.mli

@@ -35,4 +35,4 @@ val get_id : unit -> nativeint
 
 val create : string -> Caml_builtin_exceptions.exception_block
 
-val isCamlException : Obj.t -> bool
+val isCamlExceptionOrOpenVariant : Obj.t -> bool

jscomp/runtime/js_exn.ml

@@ -23,17 +23,18 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)
 
 
-type t (* =  *)
-  (* < stack : string Js.undefined ; *)
-  (*   message : string Js.undefined ;  *)
-  (*   name : string Js.undefined; *)
-  (*   fileName : string Js.undefined *)
-  (* > Js.t *)
+type t 
 
-exception Error of t 
+type exn +=  Error of t 
 
 external stack : t -> string option = ""
   [@@bs.get] [@@bs.return undefined_to_opt]
+external message : t -> string option = ""
+  [@@bs.get] [@@bs.return undefined_to_opt] 
+external name : t -> string option = ""
+  [@@bs.get] [@@bs.return undefined_to_opt] 
+external fileName : t -> string option = ""
+  [@@bs.get] [@@bs.return undefined_to_opt] 
 
 (**
    {[
@@ -44,7 +45,7 @@ external stack : t -> string option = ""
    ]}
 *)
 let internalToOCamlException (e : Obj.t) =
-  if Caml_exceptions.isCamlException e  then
+  if Caml_exceptions.isCamlExceptionOrOpenVariant e  then
     (Obj.magic e  : exn)
   else Error (Obj.magic (e : Obj.t) : t) 
 

jscomp/runtime/js_exn.mli

@@ -30,6 +30,12 @@ exception Error of t
 
 external stack : t -> string option = ""
   [@@bs.get] [@@bs.return undefined_to_opt]
+external message : t -> string option = ""
+  [@@bs.get] [@@bs.return undefined_to_opt] 
+external name : t -> string option = ""
+  [@@bs.get] [@@bs.return undefined_to_opt] 
+external fileName : t -> string option = ""
+  [@@bs.get] [@@bs.return undefined_to_opt] 
 
 (** Used by the compiler internally *)
 val internalToOCamlException : Obj.t -> exn

lib/js/caml_exceptions.js

@@ -24,7 +24,7 @@ function create(str) {
   return v;
 }
 
-function isCamlException(e) {
+function isCamlExceptionOrOpenVariant(e) {
   if (e.tag === 248) {
     return /* true */1;
   } else {
@@ -37,8 +37,8 @@ function isCamlException(e) {
   }
 }
 
-exports.caml_set_oo_id  = caml_set_oo_id;
-exports.get_id          = get_id;
-exports.create          = create;
-exports.isCamlException = isCamlException;
+exports.caml_set_oo_id               = caml_set_oo_id;
+exports.get_id                       = get_id;
+exports.create                       = create;
+exports.isCamlExceptionOrOpenVariant = isCamlExceptionOrOpenVariant;
 /* No side effect */

lib/js/js_exn.js

@@ -6,7 +6,7 @@ var Caml_exceptions = require("./caml_exceptions.js");
 var $$Error = Caml_exceptions.create("Js_exn.Error");
 
 function internalToOCamlException(e) {
-  if (Caml_exceptions.isCamlException(e)) {
+  if (Caml_exceptions.isCamlExceptionOrOpenVariant(e)) {
     return e;
   } else {
     return [