fix decode_map throwing when `null` is being passed in (#432)

2 files changed, 38 insertions, 0 deletions

diff --git a/test/gleam/dynamic_test.gleam b/test/gleam/dynamic_test.gleam
index ffd8b73..a220e6e 100644
--- a/test/gleam/dynamic_test.gleam
+++ b/test/gleam/dynamic_test.gleam
@@ -51,6 +51,35 @@ if javascript {
   }
 }
 
+if erlang {
+  pub type MyAtom {
+    ThisIsAnAtom
+  }
+
+  pub fn map_from_atom_test() {
+    ThisIsAnAtom
+    |> dynamic.from
+    |> dynamic.map(dynamic.string, dynamic.int)
+    |> should.equal(Error([
+      DecodeError(expected: "Map", found: "Atom", path: []),
+    ]))
+  }
+}
+
+if javascript {
+  external fn get_null() -> dynamic.Dynamic =
+    "../gleam_stdlib_test_ffi.mjs" "get_null"
+
+  pub fn map_from_null_test() {
+    get_null()
+    |> dynamic.from
+    |> dynamic.map(dynamic.string, dynamic.int)
+    |> should.equal(Error([
+      DecodeError(expected: "Map", found: "Null", path: []),
+    ]))
+  }
+}
+
 pub fn string_test() {
   ""
   |> dynamic.from
@@ -758,6 +787,11 @@ pub fn map_test() {
   |> should.equal(Error([
     DecodeError(expected: "Map", found: "Function", path: []),
   ]))
+
+  Nil
+  |> dynamic.from
+  |> dynamic.map(dynamic.string, dynamic.int)
+  |> should.equal(Error([DecodeError(expected: "Map", found: "Nil", path: [])]))
 }
 
 pub fn shallow_list_test() {
diff --git a/test/gleam_stdlib_test_ffi.mjs b/test/gleam_stdlib_test_ffi.mjs
index 68922c9..c859093 100755
--- a/test/gleam_stdlib_test_ffi.mjs
+++ b/test/gleam_stdlib_test_ffi.mjs
@@ -6,3 +6,7 @@ export function uint8array(list) {
   }
   return array;
 }
+
+export function get_null() {
+  return null;
+}