Also allow structs atoms on Map.from_struct/1

Author: José Valim

lib/elixir/lib/map.ex

@@ -41,18 +41,28 @@ defmodule Map do
   @doc """
   Converts a struct to map.
 
+  It accepts the struct module or a struct itself and
+  simply removes the `__struct__` field from the struct.
+
   ## Example
 
       defmodule User do
         defstruct [:name]
       end
 
-      Map.from_struct(%User{name: "valim"})
-      #=> %{name: "valim"}
+      Map.from_struct(User)
+      #=> %{name: nil}
+
+      Map.from_struct(%User{name: "john"})
+      #=> %{name: "john"}
 
   """
-  def from_struct(struct) do
-    :maps.delete(:__struct__, struct)
+  def from_struct(struct) when is_atom(struct) do
+    :maps.remove(:__struct__, struct.__struct__)
+  end
+
+  def from_struct(%{__struct__: _} = struct) do
+    :maps.remove(:__struct__, struct)
   end
 
   def equal?(%{} = map1, %{} = map2), do: map1 === map2

lib/elixir/test/elixir/map_test.exs

@@ -125,8 +125,9 @@ defmodule MapTest do
   end
 
   test "map from struct" do
+    assert Map.from_struct(ExternalUser) == %{name: "josé", age: 27}
     assert Map.from_struct(%ExternalUser{name: "valim"}) == %{name: "valim", age: 27}
-    assert Map.from_struct(%{name: "valim"}) == %{name: "valim"}
+    assert_raise FunctionClauseError, fn -> Map.from_struct(%{name: "valim"}) end
   end
 
   defmodule LocalUser do