Allow to pass encoded params.

lib/httpoison/base.ex

@@ -149,10 +149,11 @@ defmodule HTTPoison.Base do
       @spec request(atom, binary, body, headers, Keyword.t) :: {:ok, Response.t | AsyncResponse.t}
         | {:error, Error.t}
       def request(method, url, body \\ "", headers \\ [], options \\ []) do
-        if Keyword.has_key?(options, :params) do
-          url = url <> "?" <> URI.encode_query(options[:params])
-        end
-        url = process_url(to_string(url))
+        url =
+          url
+          |> to_string()
+          |> HTTPoison.Base.append_query(options[:params])
+          |> process_url()
         body = process_request_body(body)
         headers = process_request_headers(headers)
         HTTPoison.Base.request(__MODULE__, method, url, body, headers, options, &process_status_code/1, &process_headers/1, &process_response_body/1)
@@ -362,6 +363,15 @@ defmodule HTTPoison.Base do
     end
   end
 
+  @doc false
+  def append_query(url, nil), do: url
+  def append_query(url, query) when is_binary(query) do
+    url <> "?" <> query
+  end
+  def append_query(url, query) do
+    append_query(url, URI.encode_query(query))
+  end
+
   defp build_hackney_options(module, options) do
     timeout = Keyword.get options, :timeout
     recv_timeout = Keyword.get options, :recv_timeout

test/httpoison_test.exs

@@ -23,6 +23,16 @@ defmodule HTTPoisonTest do
     end
   end
 
+  test "get with serialized params" do
+    resp = HTTPoison.get("localhost:8080/get", [], params: URI.encode_query(%{foo: "bar", baz: "bong"}))
+    assert_response resp, fn(response) ->
+      args = JSX.decode!(response.body)["args"]
+      assert args["foo"] == "bar"
+      assert args["baz"] == "bong"
+      assert (args |> Map.keys |> length) == 2
+    end
+  end
+
   test "head" do
     assert_response HTTPoison.head("localhost:8080/get"), fn(response) ->
       assert response.body == ""