WP_REST_Autosaves_Controller::get_item( WP_REST_Request $request )

	public function get_item( $request ) {
		$parent_id = (int) $request->get_param( 'parent' );

		if ( $parent_id <= 0 ) {
			return new WP_Error(
				'rest_post_invalid_id',
				__( 'Invalid post parent ID.' ),
				array( 'status' => 404 )
			);
		}

		$autosave = wp_get_post_autosave( $parent_id );

		if ( ! $autosave ) {
			return new WP_Error(
				'rest_post_no_autosave',
				__( 'There is no autosave revision for this post.' ),
				array( 'status' => 404 )
			);
		}

		$response = $this->prepare_item_for_response( $autosave, $request );
		return $response;
	}