FrontendStatic: Add plug to serve frontends based on configuration.

lib/pleroma/plugs/frontend_static.ex

@@ -0,0 +1,54 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Plugs.FrontendStatic do
+  require Pleroma.Constants
+
+  @moduledoc """
+  This is a shim to call `Plug.Static` but with runtime `from` configuration`. It dispatches to the different frontends.
+  """
+  @behaviour Plug
+
+  def file_path(path, frontend_type \\ :primary) do
+    if configuration = Pleroma.Config.get([:frontends, frontend_type]) do
+      instance_static_path = Pleroma.Config.get([:instance, :static_dir], "instance/static")
+
+      Path.join([
+        instance_static_path,
+        "frontends",
+        configuration["name"],
+        configuration["ref"],
+        path
+      ])
+    else
+      nil
+    end
+  end
+
+  def init(opts) do
+    opts
+    |> Keyword.put(:from, "__unconfigured_frontend_static_plug")
+    |> Plug.Static.init()
+  end
+
+  def call(conn, opts) do
+    frontend_type = Map.get(opts, :frontend_type, :primary)
+    path = file_path("", frontend_type)
+
+    if path do
+      conn
+      |> call_static(opts, path)
+    else
+      conn
+    end
+  end
+
+  defp call_static(conn, opts, from) do
+    opts =
+      opts
+      |> Map.put(:from, from)
+
+    Plug.Static.call(conn, opts)
+  end
+end

lib/pleroma/plugs/instance_static.ex

@@ -16,11 +16,11 @@ defmodule Pleroma.Plugs.InstanceStatic do
     instance_path =
       Path.join(Pleroma.Config.get([:instance, :static_dir], "instance/static/"), path)
 
-    if File.exists?(instance_path) do
-      instance_path
-    else
+    frontend_path = Pleroma.Plugs.FrontendStatic.file_path(path, :primary)
+
+    (File.exists?(instance_path) && instance_path) ||
+      (frontend_path && File.exists?(frontend_path) && frontend_path) ||
       Path.join(Application.app_dir(:pleroma, "priv/static/"), path)
-    end
   end
 
   def init(opts) do

lib/pleroma/web/endpoint.ex

@@ -28,6 +28,17 @@ defmodule Pleroma.Web.Endpoint do
     }
   )
 
+  # Careful! No `only` restriction here, as we don't know what frontends contain.
+  plug(Pleroma.Plugs.FrontendStatic,
+    at: "/",
+    frontend_type: :primary,
+    gzip: true,
+    cache_control_for_etags: @static_cache_control,
+    headers: %{
+      "cache-control" => @static_cache_control
+    }
+  )
+
   # Serve at "/" the static files from "priv/static" directory.
   #
   # You should set gzip to true if you are running phoenix.digest