Make no_placeholder_text_policy multilang-aware

lib/pleroma/web/activity_pub/mrf/no_placeholder_text_policy.ex

@@ -6,9 +6,49 @@ defmodule Pleroma.Web.ActivityPub.MRF.NoPlaceholderTextPolicy do
   @moduledoc "Ensure no content placeholder is present (such as the dot from mastodon)"
   @behaviour Pleroma.Web.ActivityPub.MRF.Policy
 
+  @placeholders [".", "<p>.</p>"]
+
   @impl true
   def history_awareness, do: :auto
 
+  @impl true
+  def filter(
+        %{
+          "type" => type,
+          "object" => %{"contentMap" => %{} = content_map, "attachment" => _} = _child_object
+        } = object
+      )
+      when type in ["Create", "Update"] do
+    fixed_content_map =
+      Enum.reduce(content_map, %{}, fn {lang, content}, acc ->
+        if content in @placeholders do
+          acc
+        else
+          Map.put(acc, lang, content)
+        end
+      end)
+
+    fixed_object =
+      if fixed_content_map == %{} do
+        Map.put(
+          object,
+          "object",
+          object["object"]
+          |> Map.drop(["contentMap"])
+          |> Map.put("content", "")
+        )
+      else
+        object
+        |> put_in(["object", "contentMap"], fixed_content_map)
+        |> put_in(
+          ["object", "content"],
+          Pleroma.MultiLanguage.map_to_str(fixed_content_map, multiline: true)
+        )
+      end
+
+    {:ok, fixed_object}
+  end
+
   @impl true
   def filter(
         %{
@@ -16,7 +56,7 @@ def filter(
           "object" => %{"content" => content, "attachment" => _} = _child_object
         } = object
       )
-      when type in ["Create", "Update"] and content in [".", "<p>.</p>"] do
+      when type in ["Create", "Update"] and content in @placeholders do
     {:ok, put_in(object, ["object", "content"], "")}
   end
 

test/pleroma/web/activity_pub/mrf/no_placeholder_text_policy_test.exs

@@ -21,6 +21,30 @@ test "it clears content object" do
     assert res["object"]["content"] == ""
   end
 
+  test "multilang aware" do
+    message = %{
+      "type" => "Create",
+      "object" => %{
+        "content" => ".",
+        "contentMap" => %{"a" => ".", "b" => "lol"},
+        "attachment" => "image"
+      }
+    }
+
+    assert {:ok, res} = NoPlaceholderTextPolicy.filter(message)
+    assert res["object"]["content"] == "lol"
+    assert res["object"]["contentMap"] == %{"b" => "lol"}
+
+    message = %{
+      "type" => "Create",
+      "object" => %{"content" => ".", "contentMap" => %{"a" => "."}, "attachment" => "image"}
+    }
+
+    assert {:ok, res} = NoPlaceholderTextPolicy.filter(message)
+    assert res["object"]["content"] == ""
+    assert res["object"]["contentMap"] == nil
+  end
+
   test "history-aware" do
     message = %{
       "type" => "Create",