Handle nil params in get requests

lib/req.ex

@@ -544,6 +544,12 @@ defmodule Req do
     update_in(
       request.options,
       &Map.merge(&1, Map.new(options), fn
+        :params, nil, new ->
+          new
+
+        :params, _old, nil ->
+          nil
+
         :params, old, new ->
           Keyword.merge(old, new)
 

lib/req/steps.ex

@@ -534,12 +534,10 @@ defmodule Req.Steps do
     put_params(request, Req.Request.get_option(request, :params, []))
   end
 
-  defp put_params(request, []) do
-    request
-  end
+  defp put_params(request, []), do: request
 
   defp put_params(request, params) do
-    encoded = URI.encode_query(params)
+    encoded = URI.encode_query(params || [])
 
     update_in(request.url.query, fn
       nil -> encoded

test/req_test.exs

@@ -95,4 +95,28 @@ defmodule ReqTest do
     resp = Req.get!(origin_url, into: :self)
     assert Req.put!(echo_url, body: resp.body).body == "foobarbaz"
   end
+
+  test "merge params" do
+    req = Req.new(url: "/", params: [a: 1])
+    assert %{options: %{params: [a: 1, b: 2]}} = Req.merge(req, params: [b: 2])
+  end
+
+  test "merge with empty params" do
+    req = Req.new(url: "/", params: nil)
+    assert %{options: %{params: [a: 1]}} = Req.merge(req, params: [a: 1])
+
+    req = Req.new(url: "/", params: [a: 1])
+    assert %{options: %{params: nil}} = Req.merge(req, params: nil)
+  end
+
+  test "request with empty params", c do
+    Bypass.expect(c.bypass, "GET", "/", fn conn ->
+      Plug.Conn.send_resp(conn, 200, "")
+    end)
+
+
+    assert {:ok, %Req.Response{}} = Req.get(Req.new(url: c.url, params: [a: 1]), params: nil)
+    assert {:ok, %Req.Response{}} = Req.get(Req.new(url: c.url, params: nil), params: [a: 1])
+    assert %Req.Response{status: 200} = Req.get!(c.url, params: nil)
+  end
 end