lib/pleroma/web/common_api/utils.ex

@@ -37,7 +37,7 @@ def attachments_from_ids_no_descs([]), do: []
 
   def attachments_from_ids_no_descs(ids) do
     Enum.map(ids, fn media_id ->
-      case Repo.get(Object, media_id) do
+      case get_attachment(media_id) do
         %Object{data: data} -> data
         _ -> nil
       end
@@ -51,13 +51,17 @@ def attachments_from_ids_descs(ids, descs_str) do
     {_, descs} = Jason.decode(descs_str)
 
     Enum.map(ids, fn media_id ->
-      with %Object{data: data} <- Repo.get(Object, media_id) do
+      with %Object{data: data} <- get_attachment(media_id) do
         Map.put(data, "name", descs[media_id])
       end
     end)
     |> Enum.reject(&is_nil/1)
   end
 
+  defp get_attachment(media_id) do
+    Repo.get(Object, media_id)
+  end
+
   @spec get_to_and_cc(ActivityDraft.t()) :: {list(String.t()), list(String.t())}
 
   def get_to_and_cc(%{in_reply_to_conversation: %Participation{} = participation}) do

lib/pleroma/web/mastodon_api/views/status_view.ex

@@ -529,10 +529,19 @@ def render("attachment.json", %{attachment: attachment}) do
         true -> "unknown"
       end
 
-    <<hash_id::signed-32, _rest::binary>> = :crypto.hash(:md5, href)
+    attachment_id =
+      with {_, ap_id} when is_binary(ap_id) <- {:ap_id, attachment["id"]},
+           {_, %Object{data: _object_data, id: object_id}} <-
+             {:object, Object.get_by_ap_id(ap_id)} do
+        to_string(object_id)
+      else
+        _ ->
+          <<hash_id::signed-32, _rest::binary>> = :crypto.hash(:md5, href)
+          to_string(attachment["id"] || hash_id)
+      end
 
     %{
-      id: to_string(attachment["id"] || hash_id),
+      id: attachment_id,
       url: href,
       remote_url: href,
       preview_url: href_preview,

test/pleroma/web/mastodon_api/controllers/status_controller_test.exs

@@ -2129,6 +2129,25 @@ test "it updates the status", %{conn: conn, user: user} do
       assert response["spoiler_text"] == "lol"
     end
 
+    test "it updates the attachments", %{conn: conn, user: user} do
+      attachment = insert(:attachment, user: user)
+      attachment_id = to_string(attachment.id)
+
+      {:ok, activity} = CommonAPI.post(user, %{status: "mew mew #abc", spoiler_text: "#def"})
+
+      response =
+        conn
+        |> put_req_header("content-type", "application/json")
+        |> put("/api/v1/statuses/#{activity.id}", %{
+          "status" => "mew mew #abc",
+          "spoiler_text" => "#def",
+          "media_ids" => [attachment_id]
+        })
+        |> json_response_and_validate_schema(200)
+
+      assert [%{"id" => ^attachment_id}] = response["media_attachments"]
+    end
+
     test "it does not update visibility", %{conn: conn, user: user} do
       {:ok, activity} =
         CommonAPI.post(user, %{

test/support/factory.ex

@@ -111,6 +111,18 @@ def note_factory(attrs \\ %{}) do
     }
   end
 
+  def attachment_factory(attrs \\ %{}) do
+    user = attrs[:user] || insert(:user)
+
+    data =
+      attachment_data(user.ap_id, nil)
+      |> Map.put("id", Pleroma.Web.ActivityPub.Utils.generate_object_id())
+
+    %Pleroma.Object{
+      data: merge_attributes(data, Map.get(attrs, :data, %{}))
+    }
+  end
+
   def attachment_note_factory(attrs \\ %{}) do
     user = attrs[:user] || insert(:user)
     {length, attrs} = Map.pop(attrs, :length, 1)