Support redirecting by object ID in static FE.

This matches the behavior of pleroma-fe better.

Fixes #1412.

lib/pleroma/web/static_fe/static_fe_controller.ex

@@ -119,11 +119,26 @@ def show(%{assigns: %{username_or_id: username_or_id}} = conn, params) do
     end
   end
 
+  def show(%{assigns: %{object_id: _}} = conn, _params) do
+    url = Helpers.url(conn) <> conn.request_path
+    case Activity.get_create_by_object_ap_id_with_object(url) do
+      %Activity{} = activity ->
+        redirect(conn, to: "/notice/#{activity.id}")
+        _ ->
+        conn
+        |> put_status(404)
+        |> render("error.html", %{message: "Post not found.", meta: ""})
+    end
+  end
+
   def assign_id(%{path_info: ["notice", notice_id]} = conn, _opts),
     do: assign(conn, :notice_id, notice_id)
 
   def assign_id(%{path_info: ["users", user_id]} = conn, _opts),
     do: assign(conn, :username_or_id, user_id)
 
+  def assign_id(%{path_info: ["objects", object_id]} = conn, _opts),
+    do: assign(conn, :object_id, object_id)
+
   def assign_id(conn, _opts), do: conn
 end

test/web/static_fe/static_fe_controller_test.exs

@@ -1,5 +1,6 @@
 defmodule Pleroma.Web.StaticFE.StaticFEControllerTest do
   use Pleroma.Web.ConnCase
+  alias Pleroma.Activity
   alias Pleroma.Web.ActivityPub.Transmogrifier
   alias Pleroma.Web.CommonAPI
 
@@ -128,6 +129,20 @@ test "shows the whole thread", %{conn: conn} do
       assert html =~ "voyages"
     end
 
+    test "redirect by AP object ID", %{conn: conn} do
+      user = insert(:user)
+
+      {:ok, %Activity{data: %{"object" => object_url}}} =
+        CommonAPI.post(user, %{"status" => "beam me up"})
+
+      conn =
+        conn
+        |> put_req_header("accept", "text/html")
+        |> get(URI.parse(object_url).path)
+
+      assert html_response(conn, 302) =~ "redirected"
+    end
+
     test "404 when notice not found", %{conn: conn} do
       conn =
         conn