Stream out hashtag follows

lib/pleroma/hashtag.ex

@@ -10,6 +10,7 @@ defmodule Pleroma.Hashtag do
 
   alias Ecto.Multi
   alias Pleroma.Hashtag
+  alias Pleroma.User.HashtagFollow
   alias Pleroma.Object
   alias Pleroma.Repo
 
@@ -111,4 +112,19 @@ defmodule Pleroma.Hashtag do
       {:ok, deleted_count}
     end
   end
+
+  def get_followers(%Hashtag{id: hashtag_id}) do
+    from(hf in HashtagFollow)
+    |> where([hf], hf.hashtag_id == ^hashtag_id)
+    |> join(:inner, [hf], u in assoc(hf, :user))
+    |> select([hf, u], u.id)
+    |> Repo.all()
+  end
+
+  def get_recipients_for_activity(%Pleroma.Activity{object: %{hashtags: tags}}) do
+    tags
+    |> Enum.map(&get_followers/1)
+    |> List.flatten()
+    |> Enum.uniq()
+  end
 end

lib/pleroma/web/streamer.ex

@@ -17,6 +17,7 @@ defmodule Pleroma.Web.Streamer do
   alias Pleroma.Web.OAuth.Token
   alias Pleroma.Web.Plugs.OAuthScopesPlug
   alias Pleroma.Web.StreamerView
+  require Pleroma.Constants
 
   @mix_env Mix.env()
   @registry Pleroma.Web.StreamerRegistry
@@ -252,7 +253,17 @@ defmodule Pleroma.Web.Streamer do
       User.get_recipients_from_activity(item)
       |> Enum.map(fn %{id: id} -> "user:#{id}" end)
 
-    Enum.each(recipient_topics, fn topic ->
+    hashtag_recipients =
+      if Pleroma.Constants.as_public() in item.recipients do
+        Pleroma.Hashtag.get_recipients_for_activity(item)
+        |> Enum.map(fn id -> "user:#{id}" end)
+      else
+        []
+      end
+
+    all_recipients = Enum.uniq(recipient_topics ++ hashtag_recipients)
+
+    Enum.each(all_recipients, fn topic ->
       push_to_socket(topic, item)
     end)
   end