Add optional message argument to Result.getOrThrow and improve default error message

Author: mediremi

lib/es6/Stdlib_Result.js

@@ -1,14 +1,13 @@
 
 
+import * as Stdlib_JsError from "./Stdlib_JsError.js";
 
-function getOrThrow(x) {
+function getOrThrow(x, message) {
   if (x.TAG === "Ok") {
     return x._0;
+  } else {
+    return Stdlib_JsError.panic(message !== undefined ? message : "Result.getOrThrow called for Error value");
   }
-  throw {
-    RE_EXN_ID: "Not_found",
-    Error: new Error()
-  };
 }
 
 function mapOr(opt, $$default, f) {

lib/js/Stdlib_Result.js

@@ -1,14 +1,13 @@
 'use strict';
 
+let Stdlib_JsError = require("./Stdlib_JsError.js");
 
-function getOrThrow(x) {
+function getOrThrow(x, message) {
   if (x.TAG === "Ok") {
     return x._0;
+  } else {
+    return Stdlib_JsError.panic(message !== undefined ? message : "Result.getOrThrow called for Error value");
   }
-  throw {
-    RE_EXN_ID: "Not_found",
-    Error: new Error()
-  };
 }
 
 function mapOr(opt, $$default, f) {

runtime/Stdlib_Result.res

@@ -23,10 +23,16 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
 type t<'res, 'err> = result<'res, 'err> = Ok('res) | Error('err)
 
-let getOrThrow = x =>
+let getOrThrow = (x, ~message=?) =>
   switch x {
   | Ok(x) => x
-  | Error(_) => throw(Not_found)
+  | Error(_) =>
+    Stdlib_JsError.panic(
+      switch message {
+      | None => "Result.getOrThrow called for Error value"
+      | Some(message) => message
+      },
+    )
   }
 
 let getExn = getOrThrow

runtime/Stdlib_Result.resi

@@ -48,33 +48,43 @@
 type t<'res, 'err> = result<'res, 'err> = Ok('res) | Error('err)
 
 /**
-  `getExn(res)`: when `res` is `Ok(n)`, returns `n` when `res` is `Error(m)`, raise an exception
+  `getExn(res, ~message=?)` returns `n` if `res` is `Ok(n)`, otherwise throws an exception with the message provided, or a generic message if no message was provided.
 
   ```res example
   Result.getExn(Result.Ok(42)) == 42
 
   switch Result.getExn(Error("Invalid data")) {
-  | exception Not_found => assert(true)
+  | exception _ => assert(true)
+  | _ => assert(false)
+  }
+
+  switch Result.getExn(Error("Invalid data"), ~message="was Error!") {
+  | exception _ => assert(true) // Throws a JsError with the message "was Error!"
   | _ => assert(false)
   }
   ```
 */
 @deprecated("Use 'getOrThrow' instead")
-let getExn: result<'a, 'b> => 'a
+let getExn: (result<'a, 'b>, ~message: string=?) => 'a
 
 /**
-  `getOrThrow(res)`: when `res` is `Ok(n)`, returns `n` when `res` is `Error(m)`, raise an exception
+  `getOrThrow(res, ~message=?)` returns `n` if `res` is `Ok(n)`, otherwise throws an exception with the message provided, or a generic message if no message was provided.
 
   ```res example
   Result.getOrThrow(Result.Ok(42)) == 42
 
   switch Result.getOrThrow(Error("Invalid data")) {
-  | exception Not_found => assert(true)
+  | exception _ => assert(true)
+  | _ => assert(false)
+  }
+
+  switch Result.getOrThrow(Error("Invalid data"), ~message="was Error!") {
+  | exception _ => assert(true) // Throws a JsError with the message "was Error!"
   | _ => assert(false)
   }
   ```
 */
-let getOrThrow: result<'a, 'b> => 'a
+let getOrThrow: (result<'a, 'b>, ~message: string=?) => 'a
 
 /**
 `mapOr(res, default, f)`: When res is `Ok(n)`, returns `f(n)`, otherwise `default`.