From e1d0419ef3f66d79fcfc038419192ced50cba2ac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eric=20Meadows-J=C3=B6nsson?=
 <eric.meadows.jonsson@gmail.com>
Date: Mon, 14 Sep 2026 01:15:28 +0200
Subject: [PATCH] Return responses before an error in the order they were
 parsed

HTTP1.handle_data/2 and the HTTP2 stream/2 and recv/3 catch clauses
reversed the accumulated responses only on the success path, so the
responses in {:error, conn, error, responses} came back newest first.
The docs describe them as the responses parsed before the error.
---
 lib/mint/http1.ex             |  2 +-
 lib/mint/http2.ex             |  4 ++--
 test/mint/http1/conn_test.exs | 13 ++++++++++++-
 test/mint/http2/conn_test.exs | 23 ++++++++++++++++++++++-
 4 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/lib/mint/http1.ex b/lib/mint/http1.ex
index f21cd4eb..5a10c879 100644
--- a/lib/mint/http1.ex
+++ b/lib/mint/http1.ex
@@ -550,7 +550,7 @@ defmodule Mint.HTTP1 do
 
       {:error, conn, reason, responses} ->
         conn = internal_close(conn)
-        {:error, conn, reason, responses}
+        {:error, conn, reason, Enum.reverse(responses)}
     end
   end
 
diff --git a/lib/mint/http2.ex b/lib/mint/http2.ex
index 673f58b8..6a89b9a2 100644
--- a/lib/mint/http2.ex
+++ b/lib/mint/http2.ex
@@ -1045,7 +1045,7 @@ defmodule Mint.HTTP2 do
         other
     end
   catch
-    :throw, {:mint, conn, error, responses} -> {:error, conn, error, responses}
+    :throw, {:mint, conn, error, responses} -> {:error, conn, error, Enum.reverse(responses)}
   end
 
   def stream(%__MODULE__{}, _message) do
@@ -1091,7 +1091,7 @@ defmodule Mint.HTTP2 do
         {:error, %{conn | state: :closed}, error, _responses = []}
     end
   catch
-    :throw, {:mint, conn, error, responses} -> {:error, conn, error, responses}
+    :throw, {:mint, conn, error, responses} -> {:error, conn, error, Enum.reverse(responses)}
   end
 
   def recv(_conn, _byte_count, _timeout) do
diff --git a/test/mint/http1/conn_test.exs b/test/mint/http1/conn_test.exs
index 44453eda..de7f5011 100644
--- a/test/mint/http1/conn_test.exs
+++ b/test/mint/http1/conn_test.exs
@@ -217,6 +217,17 @@ defmodule Mint.HTTP1Test do
     assert_closed_and_released(conn)
   end
 
+  test "responses before an error are returned in order", %{conn: conn} do
+    {:ok, conn, ref} = HTTP1.request(conn, "GET", "/", [], nil)
+    response = "HTTP/1.1 200 OK\r\ntransfer-encoding: chunked\r\n\r\n5\r\nhello\r\nXX"
+
+    assert {:error, conn, %HTTPError{reason: :invalid_chunk_size}, responses} =
+             HTTP1.stream(conn, {:tcp, conn.socket, response})
+
+    assert [{:status, ^ref, 200}, {:headers, ^ref, _}, {:data, ^ref, "hello"}] = responses
+    assert_closed_and_released(conn)
+  end
+
   test "connection: close", %{conn: conn} do
     {:ok, conn, ref} = HTTP1.request(conn, "GET", "/", [], nil)
     response = "HTTP/1.1 200 OK\r\ncontent-length: 1\r\nconnection: close\r\n\r\nX"
@@ -572,7 +583,7 @@ defmodule Mint.HTTP1Test do
         "1\r\nX\r\n0\r\nfoo: " <> String.duplicate("x", 25) <> "\r\n"
 
     assert {:error, _conn, %HTTPError{reason: {:max_header_list_size_exceeded, 32, 30}},
-            [{:data, _, "X"}, {:headers, _, _}, {:status, _, 200}]} =
+            [{:status, _, 200}, {:headers, _, _}, {:data, _, "X"}]} =
              HTTP1.stream(conn, {:tcp, conn.socket, response})
   end
 
diff --git a/test/mint/http2/conn_test.exs b/test/mint/http2/conn_test.exs
index 12f4a901..0dac8a54 100644
--- a/test/mint/http2/conn_test.exs
+++ b/test/mint/http2/conn_test.exs
@@ -545,6 +545,27 @@ defmodule Mint.HTTP2Test do
       assert HTTP2.open?(conn, :read)
     end
 
+    test "responses before a GOAWAY error are returned in order", %{conn: conn} do
+      {conn, ref} = open_request(conn)
+
+      assert_recv_frames [headers(stream_id: stream_id)]
+
+      assert {:error, %HTTP2{}, error, responses} =
+               stream_frames(conn, [
+                 headers(
+                   stream_id: stream_id,
+                   hbf: server_encode_headers([{":status", "200"}]),
+                   flags: set_flags(:headers, [:end_headers])
+                 ),
+                 data(stream_id: stream_id, data: "hello", flags: set_flags(:data, [])),
+                 goaway(last_stream_id: stream_id, error_code: :protocol_error, debug_data: "")
+               ])
+
+      assert_http2_error error, {:server_closed_connection, :protocol_error, ""}
+
+      assert [{:status, ^ref, 200}, {:headers, ^ref, []}, {:data, ^ref, "hello"}] = responses
+    end
+
     test "with GOAWAY with :no_error and responses after the GOAWAY frame", %{conn: conn} do
       {conn, ref} = open_request(conn)
 
@@ -2067,7 +2088,7 @@ defmodule Mint.HTTP2Test do
                  window_update(stream_id: stream_id, window_size_increment: 1000)
                ])
 
-      assert Enum.reverse(responses) == [
+      assert responses == [
                {:status, ref, 200},
                {:headers, ref, []},
                {:data, ref, ""},