Add UserFetcherPlug.

lib/pleroma/plugs/user_fetcher_plug.ex

@@ -0,0 +1,34 @@
+defmodule Pleroma.Plugs.UserFetcherPlug do
+  import Plug.Conn
+  alias Pleroma.Repo
+  alias Pleroma.User
+
+  def init(options) do
+    options
+  end
+
+  def call(conn, options) do
+    with %{auth_credentials: %{username: username}} <- conn.assigns,
+         {:ok, %User{} = user} <- user_fetcher(username) do
+      conn
+      |> assign(:auth_user, user)
+    else
+      _ -> conn
+    end
+  end
+
+  defp user_fetcher(username_or_email) do
+    {
+      :ok,
+      cond do
+        # First, try logging in as if it was a name
+        user = Repo.get_by(User, %{nickname: username_or_email}) ->
+          user
+
+        # If we get nil, we try using it as an email
+        user = Repo.get_by(User, %{email: username_or_email}) ->
+          user
+      end
+    }
+  end
+end