fix: ensure adapter is set (#717)

lib/tesla.ex

@@ -105,8 +105,9 @@ defmodule Tesla do
   end
 
   defp prepare(module, %{pre: pre, post: post} = client, options) do
-    env = struct(Env, options ++ [__module__: module, __client__: client])
-    stack = pre ++ module.__middleware__() ++ post ++ [effective_adapter(module, client)]
+    adapter = effective_adapter(module, client)
+    env = struct(Env, options ++ [__module__: module, __client__: %{client | adapter: adapter}])
+    stack = pre ++ module.__middleware__() ++ post ++ [adapter]
     {env, stack}
   end
 

test/tesla_test.exs

@@ -49,7 +49,7 @@ defmodule TeslaTest do
       :ok
     end
 
-    test "defauilt adapter" do
+    test "default adapter" do
       assert Tesla.effective_adapter(EmptyClient) == {Tesla.Adapter.Httpc, :call, [[]]}
     end
 
@@ -63,6 +63,11 @@ defmodule TeslaTest do
       assert Tesla.effective_adapter(ModuleAdapterClient) == {Tesla.Mock, :call, [[]]}
     end
 
+    test "ensure adapter is set" do
+      assert {:ok, response} = ModuleAdapterClient.request(url: "test")
+      assert response.__client__.adapter
+    end
+
     test "execute module adapter" do
       assert {:ok, response} = ModuleAdapterClient.request(url: "test")
       assert response.url == "test/module/someopt"