initial request_stream implementation for Tesla

lib/reverse_proxy_plug/http_client/adapters/tesla.ex

@@ -15,6 +15,9 @@ if Code.ensure_loaded?(Tesla) do
 
     @behaviour HTTPClient
 
+    @tesla_version Application.spec(:tesla, :vsn) |> to_string() |> Version.parse!()
+    @minimum_version_for_stream Version.parse!("1.9.0")
+
     @impl HTTPClient
     def request(%HTTPClient.Request{options: options} = request) do
       {client, opts} = Keyword.pop(options, :tesla_client)
@@ -50,5 +53,25 @@ if Code.ensure_loaded?(Tesla) do
           {:error, %HTTPClient.Error{reason: error}}
       end
     end
+
+    if Version.compare(@tesla_version, @minimum_version_for_stream) in [:gt, :eq] do
+      @impl HTTPClient
+      def request_stream(%HTTPClient.Request{options: options} = req) do
+        case request(%{req | options: Keyword.merge(options, adapter: [response: :stream])}) do
+          {:ok, %HTTPClient.Response{status_code: status_code, headers: headers, body: body}} ->
+            {:ok,
+             Stream.concat(
+               [
+                 {:status, status_code},
+                 {:headers, headers}
+               ],
+               Stream.map(body, &{:chunk, &1})
+             )}
+
+          {:error, _} = error ->
+            error
+        end
+      end
+    end
   end
 end

test/reverse_proxy_plug_test.exs

@@ -87,20 +87,6 @@ defmodule ReverseProxyPlugTest do
     assert conn.resp_body == Jason.encode!(body)
   end
 
-  test "throws an error if :stream mode is used with the Tesla adapter" do
-    proxy_opts =
-      Keyword.merge(@opts,
-        client: ReverseProxyPlug.HTTPClient.Adapters.Tesla,
-        client_options: [tesla_client: Tesla.client([], ReverseProxyPlug.TeslaMock)],
-        response_mode: :stream
-      )
-
-    assert_raise ArgumentError, fn ->
-      conn(:get, "/")
-      |> ReverseProxyPlug.call(ReverseProxyPlug.init(proxy_opts))
-    end
-  end
-
   test "does not add transfer-encoding header to response" do
     headers = [{"host", "example.com"}, {"content-length", "42"}]