fix: do not raise on schemas with string keys (#4)

lib/peri.ex

@@ -300,7 +300,7 @@ defmodule Peri do
   end
 
   defp enumerable_has_key?(data, key) when is_map(data) do
-    Map.has_key?(data, key) or Map.has_key?(data, Atom.to_string(key))
+    Map.has_key?(data, key) or Map.has_key?(data, (is_binary(key) && key) || Atom.to_string(key))
   end
 
   defp enumerable_has_key?(data, key) when is_list(data) do
@@ -334,7 +334,7 @@ defmodule Peri do
 
   defp get_enumerable_value(enum, key) do
     case Access.get(enum, key) do
-      nil when is_map(enum) -> Map.get(enum, Atom.to_string(key))
+      nil when is_map(enum) -> Map.get(enum, (is_binary(key) && key) || Atom.to_string(key))
       val -> val
     end
   end

test/peri_test.exs

@@ -9,6 +9,12 @@ defmodule PeriTest do
     email: {:required, :string}
   })
 
+  defschema(:simple_mixed_keys, %{
+    "email" => {:required, :string},
+    name: :string,
+    age: :integer
+  })
+
   defschema(:nested, %{
     user: %{
       name: :string,
@@ -68,6 +74,13 @@ defmodule PeriTest do
              } =
                simple(data)
     end
+
+    test "does not raise on simple schema with string keys" do
+      data = %{name: "John", age: 30}
+
+      assert {:error, [%Peri.Error{path: ["email"], message: "is required"}]} =
+               simple_mixed_keys(data)
+    end
   end
 
   describe "nested schema validation" do