Amended oAuth strategy to resolve m/f/a tuples

lib/ueberauth/strategy/google.ex

@@ -24,17 +24,17 @@ defmodule Ueberauth.Strategy.Google do
       |> with_param(:prompt, conn)
       |> with_param(:state, conn)
 
-    opts = [redirect_uri: callback_url(conn)]
-
+    opts = oauth_client_options_from_conn(conn)
     redirect!(conn, Ueberauth.Strategy.Google.OAuth.authorize_url!(params, opts))
   end
-
+  
   @doc """
   Handles the callback from Google.
   """
   def handle_callback!(%Plug.Conn{params: %{"code" => code}} = conn) do
     params = [code: code]
-    opts = [redirect_uri: callback_url(conn)]
+    opts = oauth_client_options_from_conn(conn)
+
     case Ueberauth.Strategy.Google.OAuth.get_access_token(params, opts) do
       {:ok, token} ->
         fetch_user(conn, token)
@@ -116,7 +116,6 @@ defmodule Ueberauth.Strategy.Google do
     }
   end
 
-
   defp fetch_user(conn, token) do
     conn = put_private(conn, :google_token, token)
 
@@ -144,6 +143,17 @@ defmodule Ueberauth.Strategy.Google do
     if option(conn, key), do: Keyword.put(opts, key, option(conn, key)), else: opts
   end
 
+  defp oauth_client_options_from_conn(conn) do
+    base_options = [redirect_uri: callback_url(conn)]
+    request_options = conn.private[:ueberauth_request_options].options
+
+    case {request_options[:client_id], request_options[:client_secret]} do
+      {nil, _} -> base_options
+      {_, nil} -> base_options
+      {id, secret} -> [client_id: id, client_secret: secret] ++ base_options
+    end
+  end
+
   defp option(conn, key) do
     Keyword.get(options(conn), key, Keyword.get(default_options(), key))
   end

lib/ueberauth/strategy/google/oauth.ex

@@ -25,13 +25,8 @@ defmodule Ueberauth.Strategy.Google.OAuth do
   These options are only useful for usage outside the normal callback phase of Ueberauth.
   """
   def client(opts \\ []) do
-    config = Application.get_env(:ueberauth, Ueberauth.Strategy.Google.OAuth)
-
-    opts =
-      @defaults
-      |> Keyword.merge(opts)
-      |> Keyword.merge(config)
-
+    config = Application.get_env(:ueberauth, __MODULE__, [])
+    opts = @defaults |> Keyword.merge(opts) |> Keyword.merge(config) |> resolve_values()
     OAuth2.Client.new(opts)
   end
 
@@ -75,4 +70,13 @@ defmodule Ueberauth.Strategy.Google.OAuth do
     |> put_header("Accept", "application/json")
     |> OAuth2.Strategy.AuthCode.get_token(params, headers)
   end
+
+  defp resolve_values(list) do
+    for {key, value} <- list do
+      {key, resolve_value(value)}
+    end
+  end
+
+  defp resolve_value({m, f, a}) when is_atom(m) and is_atom(f), do: apply(m, f, a)
+  defp resolve_value(v), do: v
 end