Error 500 when moving posts

zogstrip · June 19, 2026, 5:50pm

@here there’s a 55% chance this will fix the issue

github.com/discourse/discourse-activity-pub

FIX: Reuse a topic's tombstoned collection when moving posts in (#319)

main ← fix/move-posts-tombstoned-collection

merged 07:00PM - 19 Jun 26 UTC

ZogStriP

+184 -294

### What Moving one or more posts into a `full_topic` topic could raise `Active…Record::RecordNotUnique` and surface to the user as an HTTP 500 — from core's `TopicsController#move_posts`, which only rescues `RecordInvalid` / `RecordNotSaved`, so anything else becomes a 500. Reported on Meta: https://meta.discourse.org/t/error-500-when-moving-posts/397654 ### Why ActivityPub records are hidden once tombstoned, via `IdentifierValidations`' `default_scope { where.not(ap_type: Tombstone.type) }`. The row still exists, though, and still occupies the unique `(model_type, model_id)` index (`unique_activity_pub_collection_models`). The `:first_post_moved` / `:post_moved` handlers check `!topic.activity_pub_object` — which the default scope reports as `nil` for a tombstoned collection — and call `create_activity_pub_collection!`, which blindly inserts a second collection for the same topic and collides on the unique index. It's data-dependent (the destination topic's collection must have been tombstoned previously, e.g. via a delete/restore cycle), which matches the intermittent, "no visible preconditions" reports. ### How `create_activity_pub_collection!` now looks the collection up `unscoped`, restores it when tombstoned, and reuses it instead of inserting a duplicate. This makes the method idempotent for all of its callers, and preserves the collection's `ap_id` (its federation identity) rather than orphaning it. ### Tests - Adds a regression test for moving posts into a topic whose collection was tombstoned. - A second commit simplifies the `move_posts` topic specs — collapsing the per-scenario example fan-out into one example each, with `:aggregate_failures` on the group. Same coverage, 38 → 14 examples, roughly half the runtime.

Topic		Replies	Views
Moderator move post, get 500 internal error, how to troubleshoot Support	10	1241	October 14, 2019
Move posts 500 error due to constraint Bug	2	733	January 10, 2020
500 Error: There was an error moving posts Bug	3	382	October 25, 2023
Can not move any reply into an existing topic Bug	4	992	October 9, 2019
"There was an error moving posts" Bug	2	144	December 12, 2024

Error 500 when moving posts

Related topics