Changeset 62311

Timestamp:

05/06/2026 09:55:18 PM (5 months ago)

Author:

dmsnell

Message:

RTC: Promote auto-draft posts on first autosave for collaborative sessions to avoid post loss.

When an RTC session in the editor saves edits on a draft post, they always save into an autosave revision. This prevents a sync but where storing to the post itself would lead to duplicate edits. This was set in wordpress/gutenberg commit 9df142b839320316b406ee1a02e23704d42f8719. However, there is an exception to this rule: the first session to save edits needs to promote the autosave revision into a real draft post, if a post doesn’t exist. The reason is that WordPress hides autosaves.

That is, multiple people could be editing a draft post and then once they close it, never be able to find it again. While the data is still in the database, this is a loss of the post from a practical standpoint.

This change introduces an exception where the first time a collaborative session is saving draft edits, the autodraft is promoted to a real draft post, making it visible in the post list.

AI Disclaimer: This bug was detected in a fuzzing system built by AI models and the fix was first proposed by an AI model.

Developed in: ​https://github.com/WordPress/gutenberg/pull/77865
Discussed in: https://core.trac.wordpress.org/ticket/65138
See also: ​https://github.com/WordPress/gutenberg/pull/77716

Follow-up to [61680].
Props danluu, dmsnell.
See #65138.

Location:

trunk

Files:

• src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php (modified) (1 diff)
• tests/phpunit/tests/collaboration/restAutosavesController.php (added)

trunk/src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php

@@ -230 +230 @@
                 }
 
-                $post_lock = wp_check_post_lock( $post->ID );
-                $is_draft  = 'draft' === $post->post_status || 'auto-draft' === $post->post_status;
+                $post_lock_is_active      = wp_check_post_lock( $post->ID );
+                $is_auto_draft            = 'auto-draft' === $post->post_status;
+                $is_draft                 = 'draft' === $post->post_status || $is_auto_draft;
+                $is_collaboration_enabled = wp_is_collaboration_enabled();
 
                 /*
-                 * In the context of real-time collaboration, all peers are effectively
-                 * authors and we don't want to vary behavior based on whether they are the
-                 * original author. Always target an autosave revision.
+                 * When a post is still in draft form, updates from the author can directly update the post.
+                 * Other autosaves must be stored as per-user autosave revisions.
                  *
-                 * This avoids the following issue when real-time collaboration is enabled:
+                 * When RTC is active, however, regular draft autosaves must not update the parent post directly.
+                 * Since all peers are sharing a persisted editing state (a shared CRDT), it’s important that
+                 * they all store updates in a revision. If edits were applied to the post, then upon the next
+                 * editor reload, it would appear as though the post had been updated externally, and those same
+                 * changes would be re-applied to the CRDT, duplicating the edits.
                  *
-                 * - Autosaves from the original author (if they have the post lock) will
-                 *   target the saved post.
-                 *
-                 * - Autosaves from other users are applied to a post revision.
-                 *
-                 * - If any user reloads a post, they load changes from the author's autosave.
-                 *
-                 * - The saved post has now diverged from the persisted CRDT document. The
-                 *   content (and/or title or excerpt) are now "ahead" of the persisted CRDT
-                 *   document.
-                 *
-                 * - When the persisted CRDT document is loaded, a diff is computed against
-                 *   the saved post. This diff is then applied to the in-memory CRDT
-                 *   document, which can lead to duplicate inserts or deletions.
+                 * The one caveat for RTC is that the first peer to store an edit must promote an auto-draft
+                 * into a real draft post. If this doesn’t happen then the peers may continue to make edits
+                 * but the draft will be lost, as auto-drafts are not listed in post views.
                  */
-                $is_collaboration_enabled = wp_is_collaboration_enabled();
-
-                if ( $is_draft && (int) $post->post_author === $user_id && ! $post_lock && ! $is_collaboration_enabled ) {
-                        /*
-                         * Draft posts for the same author: autosaving updates the post and does not create a revision.
-                         * Convert the post object to an array and add slashes, wp_update_post() expects escaped array.
-                         */
+                $can_update_author_draft_post = (
+                        $is_draft &&
+                        (int) $post->post_author === $user_id &&
+                        ! $is_collaboration_enabled
+                );
+
+                $can_promote_auto_draft_post = (
+                        $is_auto_draft &&
+                        $is_collaboration_enabled &&
+                        current_user_can( 'edit_post', $post->ID )
+                );
+
+                $should_update_parent_draft_post = (
+                        $can_promote_auto_draft_post ||
+                        ( ! $post_lock_is_active && $can_update_author_draft_post )
+                );
+
+                if ( $should_update_parent_draft_post ) {
                         $autosave_id = wp_update_post( wp_slash( (array) $prepared_post ), true );
                 } else {
-                        // Non-draft posts: create or update the post autosave. Pass the meta data.
                         $autosave_id = $this->create_post_autosave( (array) $prepared_post, (array) $request->get_param( 'meta' ) );
                 }