Handle stream_handlers in a single place

Author: José Valim

lib/plug/cowboy.ex

@@ -53,7 +53,6 @@ defmodule Plug.Cowboy do
     {cowboy_options, non_keyword_options} = Enum.split_with(cowboy_options, &match?({_, _}, &1))
 
     cowboy_options
-    |> set_compress()
     |> normalize_cowboy_options(scheme)
     |> to_args(scheme, plug, plug_opts, non_keyword_options)
   end
@@ -205,27 +204,6 @@ defmodule Plug.Cowboy do
     apply(:cowboy, start, args(scheme, plug, opts, cowboy_options))
   end
 
-  @default_stream_handlers [Plug.Cowboy.Stream]
-
-  defp set_compress(cowboy_options) do
-    compress = Keyword.get(cowboy_options, :compress)
-    stream_handlers = Keyword.get(cowboy_options, :stream_handlers)
-
-    case {compress, stream_handlers} do
-      {true, nil} ->
-        Keyword.put_new(cowboy_options, :stream_handlers, [
-          :cowboy_compress_h | @default_stream_handlers
-        ])
-
-      {true, _} ->
-        raise "cannot set both compress and stream_handlers at once. " <>
-                "If you wish to set compress, please add `:cowboy_compress_h` to your stream handlers."
-
-      _ ->
-        cowboy_options
-    end
-  end
-
   defp normalize_cowboy_options(cowboy_options, :http) do
     Keyword.put_new(cowboy_options, :port, 4000)
   end
@@ -249,7 +227,7 @@ defmodule Plug.Cowboy do
     dispatch = :cowboy_router.compile(dispatch || dispatch_for(plug, plug_opts))
     {extra_options, opts} = Keyword.split(opts, @protocol_options)
 
-    extra_options = Keyword.put_new(extra_options, :stream_handlers, @default_stream_handlers)
+    extra_options = set_stream_handlers(extra_options)
     protocol_and_extra_options = :maps.from_list(protocol_options ++ extra_options)
     protocol_options = Map.merge(%{env: %{dispatch: dispatch}}, protocol_and_extra_options)
     {transport_options, socket_options} = Keyword.pop(opts, :transport_options, [])
@@ -280,6 +258,28 @@ defmodule Plug.Cowboy do
     [ref || build_ref(plug, scheme), transport_options, protocol_options]
   end
 
+  @default_stream_handlers [Plug.Cowboy.Stream]
+
+  defp set_stream_handlers(opts) do
+    compress = Keyword.get(opts, :compress)
+    stream_handlers = Keyword.get(opts, :stream_handlers)
+
+    case {compress, stream_handlers} do
+      {true, nil} ->
+        Keyword.put_new(opts, :stream_handlers, [:cowboy_compress_h | @default_stream_handlers])
+
+      {true, _} ->
+        raise "cannot set both compress and stream_handlers at once. " <>
+                "If you wish to set compress, please add `:cowboy_compress_h` to your stream handlers."
+
+      {_, nil} ->
+        Keyword.put_new(opts, :stream_handlers, @default_stream_handlers)
+
+      {_, _} ->
+        opts
+    end
+  end
+
   defp build_ref(plug, scheme) do
     Module.concat(plug, scheme |> to_string |> String.upcase())
   end