From 1583363981dd861a1356aa92ad361dc922ffa4eb Mon Sep 17 00:00:00 2001
From: David Bernheisel <dbernheisel@users.noreply.github.com>
Date: Thu, 5 Oct 2023 04:51:29 -0400
Subject: [PATCH] Add :finch_private option to put into Finch.Request (#252)

---
 lib/req.ex              |  4 ++++
 lib/req/steps.ex        | 13 +++++++++++++
 test/req/steps_test.exs | 24 ++++++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/lib/req.ex b/lib/req.ex
index 0e6fe11d..e4f8d18f 100644
--- a/lib/req.ex
+++ b/lib/req.ex
@@ -293,6 +293,9 @@ defmodule Req do
 
     * `:unix_socket` - if set, connect through the given UNIX domain socket.
 
+    * `:finch_private` - a map or keyword list of private metadata to add to the Finch request. May be useful
+      for adding custom data when handling telemetry with `Finch.Telemetry`.
+
     * `:finch_request` - a function that executes the Finch request, defaults to using `Finch.request/3`.
 
   ## Examples
@@ -350,6 +353,7 @@ defmodule Req do
           :plug,
           :finch,
           :finch_request,
+          :finch_private,
           :connect_options,
           :inet6,
           :receive_timeout,
diff --git a/lib/req/steps.ex b/lib/req/steps.ex
index 5d39bc42..a2646318 100644
--- a/lib/req/steps.ex
+++ b/lib/req/steps.ex
@@ -587,6 +587,9 @@ defmodule Req.Steps do
 
     * `:unix_socket` - if set, connect through the given UNIX domain socket.
 
+    * `:finch_private` - a map or keyword list of private metadata to add to the Finch request. May be useful
+      for adding custom data when handling telemetry with `Finch.Telemetry`.
+
     * `:finch_request` - a function that executes the Finch request, defaults to using `Finch.request/3`.
 
       The function should accept 4 arguments:
@@ -675,6 +678,7 @@ defmodule Req.Steps do
     finch_request =
       Finch.build(request.method, request.url, request_headers, body)
       |> Map.replace!(:unix_socket, request.options[:unix_socket])
+      |> add_private_options(request.options[:finch_private])
 
     finch_options =
       request.options |> Map.take([:receive_timeout, :pool_timeout]) |> Enum.to_list()
@@ -838,6 +842,15 @@ defmodule Req.Steps do
     end
   end
 
+  defp add_private_options(finch_request, nil), do: finch_request
+
+  defp add_private_options(finch_request, private_options)
+       when is_list(private_options) or is_map(private_options) do
+    Enum.reduce(private_options, finch_request, fn {k, v}, acc_finch_req ->
+      Finch.Request.put_private(acc_finch_req, k, v)
+    end)
+  end
+
   defp finch_fields_to_map(fields) do
     Enum.reduce(fields, %{}, fn {name, value}, acc ->
       Map.update(acc, name, [value], &(&1 ++ [value]))
diff --git a/test/req/steps_test.exs b/test/req/steps_test.exs
index bd7f071a..3086a75f 100644
--- a/test/req/steps_test.exs
+++ b/test/req/steps_test.exs
@@ -1648,6 +1648,30 @@ defmodule Req.StepsTest do
       end
     end
 
+    def send_telemetry_metadata_pid(_name, _measurements, metadata, _) do
+      send(metadata.request.private.pid, :telemetry_private)
+      :ok
+    end
+
+    test ":finch_private", c do
+      on_exit(fn -> :telemetry.detach("#{c.test}") end)
+
+      :ok =
+        :telemetry.attach(
+          "#{c.test}",
+          [:finch, :request, :stop],
+          &__MODULE__.send_telemetry_metadata_pid/4,
+          nil
+        )
+
+      Bypass.expect(c.bypass, "GET", "/ok", fn conn ->
+        Plug.Conn.send_resp(conn, 200, "finch_private")
+      end)
+
+      assert Req.get!(c.url <> "/ok", finch_private: %{pid: self()}).body == "finch_private"
+      assert_received :telemetry_private
+    end
+
     test "into: fun" do
       %{url: url} =
         TestSocket.serve(fn socket ->