Relax result:map_error

Author: lpil

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Unreleased
 
+- `result:map_error` has been relaxed to allow mapping to a different error
+  type.
+
+## v0.3.0 - 2019-06-25
+
 - The `map_dict` module gains a `fold` function.
 - All modules moved under the `std` namespace.
 - The `http` module has been split out into the `gleam_http` package.

gen/src/[email protected]

@@ -32,8 +32,8 @@ map(Result, Fun) ->
 
 map_error(Result, Fun) ->
     case Result of
-        {ok, _} ->
-            Result;
+        {ok, X} ->
+            {ok, X};
 
         {error, Error} ->
             {error, Fun(Error)}

gen/test/gleam@result_test.erl

@@ -21,8 +21,9 @@ map_test() ->
 map_error_test() ->
     gleam@expect:equal(gleam@result:map_error({ok, 1}, fun(X) -> X + 1 end),
                        {ok, 1}),
-    gleam@expect:equal(gleam@result:map_error({error, 1}, fun(X) -> X + 1 end),
-                       {error, 2}).
+    gleam@expect:equal(gleam@result:map_error({error, 1},
+                                              fun(X) -> {<<"ok">>, X + 1} end),
+                       {error, {<<"ok">>, 2}}).
 
 flatten_test() ->
     gleam@expect:equal(gleam@result:flatten({ok, {ok, 1}}), {ok, 1}),

src/gleam/result.gleam

@@ -24,7 +24,7 @@ pub fn map(result, fun) {
 
 pub fn map_error(result, fun) {
   case result {
-  | Ok(_) -> result
+  | Ok(x) -> Ok(x)
   | Error(error) -> Error(fun(error))
   }
 }

test/gleam/result_test.gleam

@@ -37,8 +37,8 @@ pub fn map_error_test() {
   |> expect:equal(_, Ok(1))
 
   Error(1)
-  |> result:map_error(_, fn(x) { x + 1 })
-  |> expect:equal(_, Error(2))
+  |> result:map_error(_, fn(x) { {"ok", x + 1} })
+  |> expect:equal(_, Error({"ok", 2}))
 }
 
 pub fn flatten_test() {