RTC: Backport fix to prevent autosaves from losing content.

This is a companion change to WordPress/gutenberg#77865.

Author: Dan Luu

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

@@ -229,8 +229,9 @@ public function create_item( $request ) {
 			require_once ABSPATH . 'wp-admin/includes/post.php';
 		}
 
-		$post_lock = wp_check_post_lock( $post->ID );
-		$is_draft  = 'draft' === $post->post_status || 'auto-draft' === $post->post_status;
+		$post_lock     = wp_check_post_lock( $post->ID );
+		$is_auto_draft = 'auto-draft' === $post->post_status;
+		$is_draft      = 'draft' === $post->post_status || $is_auto_draft;
 
 		/*
 		 * In the context of real-time collaboration, all peers are effectively
@@ -256,10 +257,19 @@ public function create_item( $request ) {
 		 */
 		$is_collaboration_enabled = wp_is_collaboration_enabled();
 
-		if ( $is_draft && (int) $post->post_author === $user_id && ! $post_lock && ! $is_collaboration_enabled ) {
+		if (
+			$is_draft &&
+			(int) $post->post_author === $user_id &&
+			! $post_lock &&
+			( ! $is_collaboration_enabled || $is_auto_draft )
+		) {
 			/*
 			 * 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.
+			 *
+			 * Auto-drafts must still be promoted to drafts when collaboration is enabled so that a new post
+			 * survives URL loss and appears in Drafts. Regular draft autosaves remain revisions under
+			 * collaboration to keep the saved post from diverging from the persisted CRDT document.
 			 */
 			$autosave_id = wp_update_post( wp_slash( (array) $prepared_post ), true );
 		} else {

tests/phpunit/tests/collaboration/restAutosavesController.php

@@ -0,0 +1,94 @@
+<?php
+/**
+ * Tests for the collaboration autosaves REST controller override.
+ *
+ * @package gutenberg
+ * @subpackage Collaboration
+ *
+ * @group collaboration
+ * @group restapi
+ */
+class Tests_Collaboration_RestAutosavesController extends WP_UnitTestCase {
+
+	protected static int $author_id;
+
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
+		self::$author_id = $factory->user->create( array( 'role' => 'author' ) );
+	}
+
+	public static function wpTearDownAfterClass() {
+		self::delete_user( self::$author_id );
+		delete_option( 'wp_collaboration_enabled' );
+	}
+
+	public function set_up() {
+		parent::set_up();
+		wp_set_current_user( self::$author_id );
+	}
+
+	/**
+	 * Creates an empty auto-draft post.
+	 *
+	 * @return int Post ID.
+	 */
+	private function create_auto_draft(): int {
+		return self::factory()->post->create(
+			array(
+				'post_author'  => self::$author_id,
+				'post_content' => '',
+				'post_status'  => 'auto-draft',
+				'post_title'   => 'Auto Draft',
+				'post_type'    => 'post',
+			)
+		);
+	}
+
+	/**
+	 * Dispatches an autosave request for a post.
+	 *
+	 * @param int    $post_id Post ID.
+	 * @param string $title   Autosaved post title.
+	 * @param string $content Autosaved post content.
+	 * @return WP_REST_Response Autosave response.
+	 */
+	private function dispatch_autosave( int $post_id, string $title, string $content ): WP_REST_Response {
+		$request = new WP_REST_Request( 'POST', "/wp/v2/posts/{$post_id}/autosaves" );
+		$request->set_param( 'title', $title );
+		$request->set_param( 'content', $content );
+		$request->set_param( 'status', 'draft' );
+
+		return rest_get_server()->dispatch( $request );
+	}
+
+	public function test_auto_draft_autosave_promotes_parent_post_when_collaboration_is_disabled() {
+		update_option( 'wp_collaboration_enabled', 0 );
+
+		$post_id = $this->create_auto_draft();
+		$title   = 'No RTC autosaved title';
+		$content = '<!-- wp:paragraph --><p>No RTC autosaved content</p><!-- /wp:paragraph -->';
+
+		$response = $this->dispatch_autosave( $post_id, $title, $content );
+
+		$this->assertSame( 200, $response->get_status() );
+		$post = get_post( $post_id );
+		$this->assertSame( 'draft', $post->post_status );
+		$this->assertSame( $title, $post->post_title );
+		$this->assertSame( $content, $post->post_content );
+	}
+
+	public function test_auto_draft_autosave_promotes_parent_post_when_collaboration_is_enabled() {
+		update_option( 'wp_collaboration_enabled', 1 );
+
+		$post_id = $this->create_auto_draft();
+		$title   = 'RTC autosaved title';
+		$content = '<!-- wp:paragraph --><p>RTC autosaved content</p><!-- /wp:paragraph -->';
+
+		$response = $this->dispatch_autosave( $post_id, $title, $content );
+
+		$this->assertSame( 200, $response->get_status() );
+		$post = get_post( $post_id );
+		$this->assertSame( 'draft', $post->post_status );
+		$this->assertSame( $title, $post->post_title );
+		$this->assertSame( $content, $post->post_content );
+	}
+}