More descriptive error message on OAuth request_token failure (#31)

* More descriptive error message on request failure

* Request JSON responses from API, Decode JSON responses in HTTP function, Adjust error handling

* Clean up and format affected functions

lib/ueberauth/strategy/twitter.ex

@@ -101,17 +101,17 @@ defmodule Ueberauth.Strategy.Twitter do
 
   defp fetch_user(conn, token) do
     params = [{"include_entities", false}, {"skip_status", true}, {"include_email", true}]
+
     case Twitter.OAuth.get("/1.1/account/verify_credentials.json", params, token) do
       {:ok, %{status_code: 401, body: _, headers: _}} ->
         set_errors!(conn, [error("token", "unauthorized")])
-      {:ok, %{status_code: status_code, body: body, headers: _}} when status_code in 200..399 ->
-        body = Ueberauth.json_library().decode!(body)
 
+      {:ok, %{status_code: status_code, body: body, headers: _}} when status_code in 200..399 ->
         conn
         |> put_private(:twitter_token, token)
         |> put_private(:twitter_user, body)
+
       {:ok, %{status_code: _, body: body, headers: _}} ->
-        body = Ueberauth.json_library().decode!(body)
         error = List.first(body["errors"])
         set_errors!(conn, [error("token", error["message"])])
     end

lib/ueberauth/strategy/twitter/internal.ex

@@ -15,9 +15,30 @@ defmodule Ueberauth.Strategy.Twitter.OAuth.Internal do
       |> OAuther.sign(url, extraparams, creds)
       |> OAuther.header
 
-    HTTPoison.get(url, [header], params: params)
+    HTTPoison.get(url, [header, {"Accept", "application/json"}], params: params)
+    |> decode_body()
   end
 
+  def decode_body({:ok, response}) do
+    content_type =
+      Enum.find_value(response.headers, fn
+        {"content-type", val} -> val
+        _ -> nil
+      end)
+
+    case content_type do
+      "application/json" <> _ ->
+        json_body = Ueberauth.json_library().decode!(response.body)
+        json_response = %{response | body: json_body}
+        {:ok, json_response}
+
+      _ ->
+        {:ok, response}
+    end
+  end
+
+  def decode_body(other), do: other
+
   def params_decode(resp) do
     resp
     |> String.split("&", trim: true)

lib/ueberauth/strategy/twitter/oauth.ex

@@ -17,6 +17,18 @@ defmodule Ueberauth.Strategy.Twitter.OAuth do
              request_token: "/oauth/request_token",
              site: "https://api.twitter.com"]
 
+  defmodule ApiError do
+    @moduledoc "Raised on OAuth API errors."
+
+    defexception [:message, :code]
+
+    def message(e = %{code: nil}), do: e.message
+
+    def message(e) do
+      "#{e.message} (Code #{e.code})"
+    end
+  end
+
   def access_token({token, token_secret}, verifier, opts \\ []) do
     opts
     |> client()
@@ -73,19 +85,22 @@ defmodule Ueberauth.Strategy.Twitter.OAuth do
 
   defp consumer(client), do: {client.consumer_key, client.consumer_secret, :hmac_sha1}
 
-  defp decode_response({:ok, %{status_code: 200, body: body, headers: _}}) do
+  defp decode_response({:ok, %{status_code: 200, body: body}}) do
     params = Internal.params_decode(body)
     token = Internal.token(params)
     token_secret = Internal.token_secret(params)
 
     {:ok, {token, token_secret}}
   end
-  defp decode_response({:ok, %{status_code: status_code, body: _, headers: _}}) do
-    {:error, "#{status_code}"}
+
+  defp decode_response({:ok, %{status_code: status_code, body: %{"errors" => [error | _]}}}) do
+    {:error, %ApiError{message: error["message"], code: error["code"]}}
   end
+
   defp decode_response({:error, %{reason: reason}}) do
     {:error, "#{reason}"}
   end
+
   defp decode_response(error) do
     {:error, error}
   end