add optional message to Option.getExn

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - BREAKING: Use new native `bigint` type. This requires ReScript compiler version "11.1.0-rc.6" or higher. https://github.com/rescript-association/rescript-core/pull/207
 - `Int`, `Float`, `BigInt`: use optional args and deprecate `xxxWithRadix`, `xxxWithPrecision` etc. https://github.com/rescript-association/rescript-core/pull/209
+- Add optional `~message: string=?` to `Option.getExn`.
 
 ## 1.2.0
 

src/Core__Option.res

@@ -34,10 +34,16 @@ let forEach = (opt, f) =>
   | None => ()
   }
 
-let getExn = x =>
+let getExn = (x, ~message=?) =>
   switch x {
   | Some(x) => x
-  | None => raise(Not_found)
+  | None =>
+    Core__Error.panic(
+      switch message {
+      | None => "Not found."
+      | Some(message) => message
+      },
+    )
   }
 
 external getUnsafe: option<'a> => 'a = "%identity"

src/Core__Option.resi

@@ -66,18 +66,19 @@ Option.forEach(None, x => Console.log(x)) // returns ()
 let forEach: (option<'a>, 'a => unit) => unit
 
 /**
-`getExn(opt)` returns `value` if `opt` is `Some(value)`, otherwise raises an exception.
+`getExn(opt, ~message=?)` returns `value` if `opt` is `Some(value)`, otherwise raises an exception with the message provided, or a generic message if no message was provided.
 
 ```rescript
 Option.getExn(Some(3)) // 3
 Option.getExn(None) /* Raises an Error */
+Option.getExn(None, ~message="was None!") /* Raises an Error with the message "was None!" */
 ```
 
 ## Exceptions
 
 - Raises an error if `opt` is `None`
 */
-let getExn: option<'a> => 'a
+let getExn: (option<'a>, ~message: string=?) => 'a
 
 /**
 `getUnsafe(opt)` returns `value` if `opt` is `Some(value)`, otherwise `undefined`.