From 93b526c761d729808827285302f9c55d2514e1dc Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Wed, 22 Apr 2026 16:50:50 -0500
Subject: [PATCH] fix(web): suppress HEAD request logs

The log_level(%{method: \"HEAD\"}) clause never matched because
Plug.Head rewrites the method to \"GET\" before Plug.Telemetry's
register_before_send callback fires, so by log time conn.method is
\"GET\". Stash the original method in private before Plug.Head runs
and key the filter off it.
---
 lib/microwaveprop_web/endpoint.ex             | 12 +++++++-
 .../metrics_log_suppression_test.exs          | 28 +++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/lib/microwaveprop_web/endpoint.ex b/lib/microwaveprop_web/endpoint.ex
index 1586f508..24fba93e 100644
--- a/lib/microwaveprop_web/endpoint.ex
+++ b/lib/microwaveprop_web/endpoint.ex
@@ -46,6 +46,12 @@ defmodule MicrowavepropWeb.Endpoint do
 
   plug Plug.RequestId
   plug MicrowavepropWeb.Plugs.RemoteIp
+  # Plug.Head (below) rewrites method=HEAD to "GET" before
+  # Plug.Telemetry's register_before_send callback fires, so a
+  # `log_level(%{method: "HEAD"})` clause never matches. Capture
+  # the original method in private here so the log filter can still
+  # see HEAD requests and suppress them.
+  plug :stash_request_method
   plug Plug.Telemetry, event_prefix: [:phoenix, :endpoint], log: {__MODULE__, :log_level, []}
 
   plug Plug.Parsers,
@@ -71,6 +77,10 @@ defmodule MicrowavepropWeb.Endpoint do
   def log_level(%{request_path: "/live"}), do: false
   def log_level(%{request_path: "/metrics"}), do: false
   def log_level(%{request_path: "/metrics/" <> _}), do: false
-  def log_level(%{method: "HEAD"}), do: false
+  def log_level(%{private: %{original_method: "HEAD"}}), do: false
   def log_level(_conn), do: :info
+
+  defp stash_request_method(conn, _opts) do
+    Plug.Conn.put_private(conn, :original_method, conn.method)
+  end
 end
diff --git a/test/microwaveprop_web/metrics_log_suppression_test.exs b/test/microwaveprop_web/metrics_log_suppression_test.exs
index 1c18cb29..7bd686e9 100644
--- a/test/microwaveprop_web/metrics_log_suppression_test.exs
+++ b/test/microwaveprop_web/metrics_log_suppression_test.exs
@@ -71,4 +71,32 @@ defmodule MicrowavepropWeb.MetricsLogSuppressionTest do
 
     assert MicrowavepropWeb.Endpoint.log_level(rewritten) == false
   end
+
+  test "log_level/1 returns false when the original method stashed before Plug.Head was HEAD" do
+    # Plug.Head runs BEFORE Plug.Telemetry's register_before_send fires
+    # and rewrites HEAD→GET, so matching `method: \"HEAD\"` at log time
+    # never hits. Endpoint now stashes the original method in private
+    # before Plug.Head runs; assert the filter keys off it.
+    conn = %{
+      request_path: "/some/page",
+      method: "GET",
+      private: %{original_method: "HEAD"}
+    }
+
+    assert MicrowavepropWeb.Endpoint.log_level(conn) == false
+  end
+
+  test "HEAD request to a real route does not emit a Phoenix endpoint Sent log line", %{
+    conn: conn
+  } do
+    log =
+      capture_log([level: :info], fn ->
+        conn = dispatch(conn, MicrowavepropWeb.Endpoint, "HEAD", "/")
+        assert conn.status in [200, 302]
+      end)
+
+    refute log =~ "Sent 200"
+    refute log =~ "Sent 302"
+    refute log =~ "HEAD /"
+  end
 end