Raise on pipe_through if route or scope previously defined in scope

lib/phoenix/presence.ex

@@ -312,12 +312,12 @@ defmodule Phoenix.Presence do
   devices, could return:
 
       iex> MyPresence.get_by_key("room:1", "user1")
-      [%{name: "User 1", metas: [%{device: "Desktop"}, %{device: "Mobile"}]}]
+      %{name: "User 1", metas: [%{device: "Desktop"}, %{device: "Mobile"}]}
 
   Like `c:list/1`, the presence metadata is passed to the `fetch`
   callback of your presence module to fetch any additional information.
   """
-  @callback get_by_key(Phoenix.Socket.t() | topic, key :: String.t()) :: [presence]
+  @callback get_by_key(Phoenix.Socket.t() | topic, key :: String.t()) :: map() | []
 
   @doc """
   Extend presence information with additional data.

lib/phoenix/router/scope.ex

@@ -14,7 +14,8 @@ defmodule Phoenix.Router.Scope do
             private: %{},
             assigns: %{},
             log: :debug,
-            trailing_slash?: false
+            trailing_slash?: false,
+            route_defined?: false
 
   @doc """
   Initializes the scope.
@@ -61,6 +62,8 @@ defmodule Phoenix.Router.Scope do
         metadata
       end
 
+    put_top(module, %{top | route_defined?: true})
+
     Phoenix.Router.Route.build(
       line,
       kind,
@@ -120,7 +123,12 @@ defmodule Phoenix.Router.Scope do
   """
   def pipe_through(module, new_pipes) do
     new_pipes = List.wrap(new_pipes)
-    %{pipes: pipes} = top = get_top(module)
+    %{pipes: pipes, route_defined?: route_defined?} = top = get_top(module)
+
+    if route_defined? do
+      raise ArgumentError,
+            "pipe_through must be placed before any routes or scopes in the current scope"
+    end
 
     if pipe = Enum.find(new_pipes, &(&1 in pipes)) do
       raise ArgumentError,
@@ -160,7 +168,8 @@ defmodule Phoenix.Router.Scope do
     private = Keyword.get(opts, :private, %{})
     assigns = Keyword.get(opts, :assigns, %{})
 
-    update_stack(module, fn stack -> [top | stack] end)
+    put_top(module, %{top | route_defined?: true})
+    update_stack(module, fn stack -> [%{top | route_defined?: true} | stack] end)
 
     put_top(module, %Scope{
       path: top.path ++ path,

test/phoenix/router/pipeline_test.exs

@@ -158,6 +158,37 @@ defmodule Phoenix.Router.PipelineTest do
     end
   end
 
+  test "pipe_through after route or scope raises" do
+    assert_raise ArgumentError, ~r{pipe_through must be placed before any routes or scopes in the current scope}, fn ->
+      defmodule PipeThroughAfterRouteRouter do
+        use Phoenix.Router, otp_app: :phoenix
+
+        pipeline :browser do
+        end
+
+        scope "/" do
+          get "/foo", Phoenix.Router.PipelineTest.SampleController, :index
+          pipe_through :browser
+        end
+      end
+    end
+
+    assert_raise ArgumentError, ~r{pipe_through must be placed before any routes or scopes in the current scope}, fn ->
+      defmodule PipeThroughAfterScopeRouter do
+        use Phoenix.Router, otp_app: :phoenix
+
+        pipeline :browser do
+        end
+
+        scope "/" do
+          scope "/foo" do
+          end
+          pipe_through :browser
+        end
+      end
+    end
+  end
+
   test "pipeline raises on conflict" do
     assert_raise ArgumentError, ~r{there is an import from Kernel with the same name}, fn ->
       defmodule ConflictingPipeline do

test/phoenix/router/routing_test.exs

@@ -63,8 +63,10 @@ defmodule Phoenix.Router.RoutingTest do
       pipe_through :noop
       get "/plug", SomePlug, []
       get "/users/:id/raise", UserController, :raise
-      pipe_through :halt
-      get "/info", UserController, :raise
+      scope "/" do
+        pipe_through :halt
+        get "/info", UserController, :raise
+      end
     end
 
     get "/no_log", SomePlug, [], log: false