Handle empty list argument without raising error (#4686)

Author: hugobarauna

lib/ecto/repo/queryable.ex

@@ -90,6 +90,8 @@ defmodule Ecto.Repo.Queryable do
     one!(name, query_for_get_by(queryable, clauses), opts)
   end
 
+  def reload(_name, [], _opts), do: []
+
   def reload(name, [head | _] = structs, opts) when is_list(structs) do
     results = all(name, query_for_reload(structs), opts)
 
@@ -105,6 +107,8 @@ defmodule Ecto.Repo.Queryable do
     one(name, query_for_reload([struct]), opts)
   end
 
+  def reload!(_name, [], _opts), do: []
+
   def reload!(name, [head | _] = structs, opts) when is_list(structs) do
     query = query_for_reload(structs)
     results = all(name, query, opts)

test/ecto/repo_test.exs

@@ -350,6 +350,14 @@ defmodule Ecto.RepoTest do
       TestRepo.reload(struct_with_custom_source)
       assert_received {:all, %{from: %{source: {"custom_schema", MySchema}}}}
     end
+
+    test "returns empty list when given empty list" do
+      assert TestRepo.reload([]) == []
+    end
+
+    test "reload! returns empty list when given empty list" do
+      assert TestRepo.reload!([]) == []
+    end
   end
 
   defmodule DefaultOptionRepo do