compressed: Default compressed: false when streaming response body

Closes #294

lib/req/steps.ex

@@ -277,14 +277,18 @@ defmodule Req.Steps do
   Supported formats:
 
     * `gzip`
+
     * `br` (if [brotli] is installed)
+
     * `zstd` (if [ezstd] is installed)
 
   ## Request Options
 
     * `:compressed` - if set to `true`, sets the `accept-encoding` header with compression
       algorithms that Req supports. Defaults to `true`.
 
+      When streaming response body (`into: fun | collectable`), `compressed` defaults to `false`.
+
   ## Examples
 
   Req automatically decompresses response body (`decompress_body/1` step) so let's disable that by
@@ -322,7 +326,7 @@ defmodule Req.Steps do
   [ezstd]: https://hex.pm/packages/ezstd
   """
   @doc step: :request
-  def compressed(request) do
+  def compressed(%Req.Request{into: nil} = request) do
     case Req.Request.get_option(request, :compressed, true) do
       true ->
         Req.Request.put_new_header(request, "accept-encoding", supported_accept_encoding())
@@ -332,6 +336,10 @@ defmodule Req.Steps do
     end
   end
 
+  def compressed(request) do
+    request
+  end
+
   defmacrop brotli_loaded? do
     Code.ensure_loaded?(:brotli)
   end

test/req/steps_test.exs

@@ -10,6 +10,18 @@ defmodule Req.StepsTest do
 
   ## Request steps
 
+  describe "compressed" do
+    test "sets accept-encoding" do
+      req = Req.new() |> Req.Request.prepare()
+      assert req.headers["accept-encoding"] == ["zstd, br, gzip"]
+    end
+
+    test "does not set accept-encoding when streaming response body" do
+      req = Req.new(into: []) |> Req.Request.prepare()
+      refute req.headers["accept-encoding"]
+    end
+  end
+
   describe "put_base_url" do
     test "it works", c do
       Bypass.expect(c.bypass, "GET", "", fn conn ->