SideEffects: Correctly handle chat messages sent to yourself

lib/pleroma/web/activity_pub/side_effects.ex

@@ -306,6 +306,7 @@ def handle_object_creation(%{"type" => "ChatMessage"} = object, meta) do
 
       streamables =
         [[actor, recipient], [recipient, actor]]
+        |> Enum.uniq()
         |> Enum.map(fn [user, other_user] ->
           if user.local do
             {:ok, chat} = Chat.bump_or_create(user.id, other_user.ap_id)

test/pleroma/web/common_api_test.exs

@@ -95,6 +95,20 @@ test "it blocks and does not federate if outgoing blocks are disabled", %{
   describe "posting chat messages" do
     setup do: clear_config([:instance, :chat_limit])
 
+    test "it posts a self-chat" do
+      author = insert(:user)
+      recipient = author
+
+      {:ok, activity} =
+        CommonAPI.post_chat_message(
+          author,
+          recipient,
+          "remember to buy milk when milk truk arive"
+        )
+
+      assert activity.data["type"] == "Create"
+    end
+
     test "it posts a chat message without content but with an attachment" do
       author = insert(:user)
       recipient = insert(:user)