Deprecate server pushes given it is being removed from browsers and c…

…lients

lib/plug/conn.ex

@@ -1401,6 +1401,7 @@ defmodule Plug.Conn do
   resource if your certificate is not trusted. In the case of Chrome this means
   a valid cert with a SAN. See https://www.chromestatus.com/feature/4981025180483584
   """
+  @deprecated "Most browsers and clients have removed push support"
   @spec push(t, String.t(), Keyword.t()) :: t
   def push(%Conn{} = conn, path, headers \\ []) do
     adapter_push(conn, path, headers)
@@ -1411,6 +1412,7 @@ defmodule Plug.Conn do
   Pushes a resource to the client but raises if the adapter
   does not support server push.
   """
+  @deprecated "Most browsers and clients have removed push support"
   @spec push!(t, String.t(), Keyword.t()) :: t
   def push!(%Conn{adapter: {adapter, _}} = conn, path, headers \\ []) do
     case adapter_push(conn, path, headers) do

lib/plug/test.ex

@@ -145,6 +145,7 @@ defmodule Plug.Test do
       assert {"/static/application.js", [{"accept", "application/javascript"}]} in pushes
 
   """
+  @deprecated "Most browsers and clients have removed push support"
   def sent_pushes(%Conn{adapter: {Plug.Adapters.Test.Conn, %{ref: ref}}}) do
     Enum.reverse(receive_pushes(ref, []))
   end

test/plug/adapters/test/conn_test.exs

@@ -126,18 +126,6 @@ defmodule Plug.Adapters.Test.ConnTest do
     assert {103, [{"link", "</script.js>; rel=preload; as=script"}]} in informational_requests
   end
 
-  test "push adds to the pushes list" do
-    conn =
-      conn(:get, "/")
-      |> Plug.Conn.push("/static/application.css", [{"accept", "text/css"}])
-      |> Plug.Conn.push("/static/application.js", [{"accept", "application/javascript"}])
-
-    pushes = Plug.Test.sent_pushes(conn)
-
-    assert {"/static/application.css", [{"accept", "text/css"}]} in pushes
-    assert {"/static/application.js", [{"accept", "application/javascript"}]} in pushes
-  end
-
   test "full URL overrides existing conn.host" do
     conn_with_host = conn(:get, "http://www.elixir-lang.org/")
     assert conn_with_host.host == "www.elixir-lang.org"

test/plug/conn_test.exs

@@ -449,22 +449,6 @@ defmodule Plug.ConnTest do
     )
   end
 
-  test "push/3 performs a server push" do
-    conn = conn(:get, "/foo") |> push("/static/application.css", [{"accept", "text/plain"}])
-    assert {"/static/application.css", [{"accept", "text/plain"}]} in sent_pushes(conn)
-  end
-
-  test "push/3 works out the MIME type if not set" do
-    conn = conn(:get, "/foo") |> push("/static/application.css")
-    assert {"/static/application.css", [{"accept", "text/css"}]} in sent_pushes(conn)
-  end
-
-  test "push/3 will raise if the response is sent before pushing" do
-    assert_raise(Plug.Conn.AlreadySentError, fn ->
-      conn(:get, "/foo") |> send_chunked(200) |> push("/static/application.css")
-    end)
-  end
-
   test "chunk/2 raises if send_chunked/3 hasn't been called yet" do
     conn = conn(:get, "/")