lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -921,7 +921,24 @@ def prepare_attachments(object) do
   end
 
   def strip_internal_fields(object) do
-    Map.drop(object, Pleroma.Constants.object_internal_fields())
+    outer = Map.drop(object, Pleroma.Constants.object_internal_fields())
+
+    case outer do
+      %{"formerRepresentations" => %{"orderedItems" => list}} when is_list(list) ->
+        update_in(
+          outer["formerRepresentations"]["orderedItems"],
+          &Enum.map(
+            &1,
+            fn
+              item when is_map(item) -> Map.drop(item, Pleroma.Constants.object_internal_fields())
+              item -> item
+            end
+          )
+        )
+
+      _ ->
+        outer
+    end
   end
 
   defp strip_internal_tags(%{"tag" => tags} = object) do

test/pleroma/web/activity_pub/transmogrifier_test.exs

@@ -550,4 +550,58 @@ test "puts dimensions into attachment url field" do
       assert Transmogrifier.fix_attachments(object) == expected
     end
   end
+
+  describe "strip_internal_fields/1" do
+    test "it strips internal fields in formerRepresentations" do
+      original = %{
+        "formerRepresentations" => %{
+          "orderedItems" => [
+            %{"generator" => %{}}
+          ]
+        }
+      }
+
+      stripped = Transmogrifier.strip_internal_fields(original)
+
+      refute Map.has_key?(
+               Enum.at(stripped["formerRepresentations"]["orderedItems"], 0),
+               "generator"
+             )
+    end
+
+    test "it strips internal fields in maybe badly-formed formerRepresentations" do
+      original = %{
+        "formerRepresentations" => %{
+          "orderedItems" => [
+            %{"generator" => %{}},
+            "https://example.com/1"
+          ]
+        }
+      }
+
+      stripped = Transmogrifier.strip_internal_fields(original)
+
+      refute Map.has_key?(
+               Enum.at(stripped["formerRepresentations"]["orderedItems"], 0),
+               "generator"
+             )
+
+      assert Enum.at(stripped["formerRepresentations"]["orderedItems"], 1) ==
+               "https://example.com/1"
+    end
+
+    test "it ignores if formerRepresentations does not look like an OrderedCollection" do
+      original = %{
+        "formerRepresentations" => %{
+          "items" => [
+            %{"generator" => %{}}
+          ]
+        }
+      }
+
+      stripped = Transmogrifier.strip_internal_fields(original)
+
+      assert Map.has_key?(Enum.at(stripped["formerRepresentations"]["items"], 0), "generator")
+    end
+  end
 end