May be useful to handle the case when the function inside List.map fails:
let%catch func lst =
List.map (fun x ->
if x > 0 then failwith "Some problem" else x + 1) lst becomes:
let%catch func lst =
try
Ok (List.map (fun x ->
if x > 0 then failwith "Some problem" else x + 1) lst)
with
| Failure err -> Error (*[ "func: " + err ]*) (* error messages with tracing *)
(* and so on *) ...
| _ -> Error "func: Unknown error" Extension handles both top-level and “embedded” let bindings:
let foo =
let%catch wants_to_raise () = (* wrap some Stdlib function for example *)
(* some logic *)
failwith "Stdlib exception" (* call to Stdlib function that raises an exception *)
in
wants_to_raise () (* returns ('a, string) result *)Also works with “function” syntax:
let%catch wrap_function = function
| Some res -> res
| None -> failwith "function syntax works too"It basically wraps each case of the pattern matching.
let () =
match wrap_function None with
| Ok ok -> Printf.printf "Ok\n" ;
| Error err -> Printf.printf "%s\n" err ;
()
prints :
wrap_function: function syntax works tooTo instal this rewriter as opam package:
git clone https://github.com/slamko/ppx_catch.git &&
cd ppx_catch &&
dune build &&
opam install .Now to use it in your project add ppx_catch to library list and tell to use it as a preprocessor in your dune file:
(libraries
ppx_catch)
(preprocess (pps ppx_catch))For a complete dune file example see test/dune
GPL-v3.0
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent