allow users to filter out certain handle_in messages

lib/phoenix/channel.ex

@@ -332,6 +332,20 @@ defmodule Phoenix.Channel do
 
   Note that changing an event type's level doesn't affect what is logged,
   unless you set it to `false`, it affects the associated level.
+
+  To filter out logs for certain messages, you can pass a function to the
+  `:log_join` and `:log_handle_in` options. The function should return `false`
+  for messages you want to filter out, and `:debug` or `:info` for messages
+  you want to log.
+
+  For example, to filter out handle_in messages when the event name starts
+  with "ping_" and matches `%{"pong" => true}` in params:
+
+      use Phoenix.Channel, log_handle_in: &__MODULE__.filter_ping/2
+
+      def filter_ping("ping_" <> _, %{"pong" => true}), do: false
+      def filter_ping(_, _), do: :debug
+
   """
   alias Phoenix.Socket
   alias Phoenix.Channel.Server

lib/phoenix/logger.ex

@@ -343,7 +343,7 @@ defmodule Phoenix.Logger do
 
   @doc false
   def phoenix_channel_joined(_, %{duration: duration}, %{socket: socket} = metadata, _) do
-    channel_log(:log_join, socket, fn ->
+    channel_log(:log_join, metadata, fn ->
       %{result: result, params: params} = metadata
 
       [
@@ -364,7 +364,7 @@ defmodule Phoenix.Logger do
 
   @doc false
   def phoenix_channel_handled_in(_, %{duration: duration}, %{socket: socket} = metadata, _) do
-    channel_log(:log_handle_in, socket, fn ->
+    channel_log(:log_handle_in, metadata, fn ->
       %{event: event, params: params} = metadata
 
       [
@@ -382,10 +382,21 @@ defmodule Phoenix.Logger do
     end)
   end
 
-  defp channel_log(_log_option, %{topic: "phoenix" <> _}, _fun), do: :ok
+  defp channel_log(_log_option, %{socket: %{topic: "phoenix" <> _}}, _fun), do: :ok
 
-  defp channel_log(log_option, %{private: private}, fun) do
-    if level = Map.get(private, log_option) do
+  defp channel_log(log_option, %{socket: %{private: private}, event: event, params: params}, fun) do
+    log_option = Map.get(private, log_option)
+
+    level =
+      cond do
+        is_function(log_option, 2) ->
+          log_option.(event, params)
+
+        true ->
+          log_option
+      end
+
+    if level do
       Logger.log(level, fun)
     end
   end