From 7b7f1fd6b480dc1937b666a437570f07d7b8f687 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@dashbit.co>
Date: Sun, 1 Oct 2023 20:31:02 +0200
Subject: [PATCH] Revert "Add `Plug.Conn.register_before_chunk/2` (#1154)"

This reverts commit 8bff7c193aa8517e2d4c14a15df4a98dfa6c2ce7.
---
 lib/plug/conn.ex        | 43 ---------------------------------
 test/plug/conn_test.exs | 53 -----------------------------------------
 2 files changed, 96 deletions(-)

diff --git a/lib/plug/conn.ex b/lib/plug/conn.ex
index 1a0bcd53..54997b0a 100644
--- a/lib/plug/conn.ex
+++ b/lib/plug/conn.ex
@@ -551,8 +551,6 @@ defmodule Plug.Conn do
   """
   @spec chunk(t, body) :: {:ok, t} | {:error, term} | no_return
   def chunk(%Conn{adapter: {adapter, payload}, state: :chunked} = conn, chunk) do
-    conn = run_before_chunk(conn, chunk)
-
     if iodata_empty?(chunk) do
       {:ok, conn}
     else
@@ -1808,36 +1806,6 @@ defmodule Plug.Conn do
     update_in(conn.private[:before_send], &[callback | &1 || []])
   end
 
-  @doc ~S"""
-  Registers a callback to be invoked before a chunk is sent by `chunk/2`.
-
-  Callbacks are invoked in the reverse order they are registered, that is, callbacks which
-  are registered first are invoked last.
-
-  ## Examples
-
-  This example logs the size of the chunk about to be sent:
-
-      register_before_chunk(conn, fn _conn, chunk ->
-        Logger.info("Sending #{IO.iodata_length(chunk)} bytes")
-        conn
-      end)
-
-  """
-  @doc since: "1.15.0"
-  @spec register_before_chunk(t, (t, body -> t)) :: t
-  def register_before_chunk(conn, callback)
-
-  def register_before_chunk(%Conn{state: state}, _callback)
-      when state not in @unsent do
-    raise AlreadySentError
-  end
-
-  def register_before_chunk(%Conn{} = conn, callback)
-      when is_function(callback, 2) do
-    update_in(conn.private[:before_chunk], &[callback | &1 || []])
-  end
-
   @doc """
   Halts the `Plug` pipeline by preventing further plugs downstream from being
   invoked. See the docs for `Plug.Builder` for more information on halting a
@@ -1874,17 +1842,6 @@ defmodule Plug.Conn do
     %{conn | resp_headers: merge_headers(conn.resp_headers, conn.resp_cookies)}
   end
 
-  defp run_before_chunk(%Conn{private: private} = conn, chunk) do
-    initial_state = conn.state
-    conn = Enum.reduce(private[:before_chunk] || [], conn, & &1.(&2, chunk))
-
-    if conn.state != initial_state do
-      raise ArgumentError, "cannot send or change response from run_before_chunk/2 callback"
-    end
-
-    %{conn | resp_headers: merge_headers(conn.resp_headers, conn.resp_cookies)}
-  end
-
   defp merge_headers(headers, cookies) do
     Enum.reduce(cookies, headers, fn {key, opts}, acc ->
       value =
diff --git a/test/plug/conn_test.exs b/test/plug/conn_test.exs
index aaad463a..d71b6399 100644
--- a/test/plug/conn_test.exs
+++ b/test/plug/conn_test.exs
@@ -405,51 +405,6 @@ defmodule Plug.ConnTest do
     assert get_resp_header(conn, "x-body") == ["CHUNK"]
   end
 
-  test "chunk/2 runs before_chunk callbacks" do
-    pid = self()
-
-    conn(:get, "/foo")
-    |> register_before_chunk(fn conn, chunk ->
-      send(pid, {:before_chunk, 1, chunk})
-      conn
-    end)
-    |> register_before_chunk(fn conn, chunk ->
-      send(pid, {:before_chunk, 2, chunk})
-      conn
-    end)
-    |> send_chunked(200)
-    |> chunk("CHUNK")
-
-    # We need to match with n1 and n2 because if we match directly on 1 and 2 then
-    # selective receive will match on the messages even if they're out of order.
-    assert_receive {:before_chunk, n1, "CHUNK"}
-    assert_receive {:before_chunk, n2, "CHUNK"}
-    assert n1 == 2
-    assert n2 == 1
-  end
-
-  test "chunk/2 uses the updated conn from before_chunk callbacks" do
-    pid = self()
-
-    conn =
-      conn(:get, "/foo")
-      |> assign(:test_counter, 0)
-      |> register_before_chunk(fn conn, _chunk ->
-        {count, conn} = get_and_update_in(conn.assigns[:test_counter], &{&1, &1 + 1})
-        send(pid, {:before_chunk, count})
-        conn
-      end)
-      |> send_chunked(200)
-
-    assert {:ok, conn} = chunk(conn, "CHUNK")
-    assert {:ok, conn} = chunk(conn, "CHUNK")
-    assert {:ok, _conn} = chunk(conn, "CHUNK")
-
-    assert_received {:before_chunk, 0}
-    assert_received {:before_chunk, 1}
-    assert_received {:before_chunk, 2}
-  end
-
   test "inform/3 performs an informational request" do
     conn = conn(:get, "/foo") |> inform(103, [{"link", "</style.css>; rel=preload; as=style"}])
     assert {103, [{"link", "</style.css>; rel=preload; as=style"}]} in sent_informs(conn)
@@ -1454,14 +1409,6 @@ defmodule Plug.ConnTest do
     end
   end
 
-  test "register_before_chunk/2 raises when a response has already been sent" do
-    conn = send_resp(conn(:get, "/"), 200, "ok")
-
-    assert_raise Plug.Conn.AlreadySentError, fn ->
-      register_before_chunk(conn, fn _ -> nil end)
-    end
-  end
-
   test "does not delegate to connections' adapter's chunk/2 when called with an empty chunk" do
     defmodule RaisesOnEmptyChunkAdapter do
       defdelegate send_chunked(state, status, headers), to: Plug.Adapters.Test.Conn