WordPress preview trashed posts

preview.php

<?php

class Preview {

	/**
	 * Register WordPress hooks and filters
	 *
	 * @return void
	 */
	public function register() {
		add_filter( 'post_row_actions', [ $this, 'post_row_actions' ], 10, 2 );

		if ( ! is_admin() ) {
			add_filter( 'pre_get_posts', [ $this, 'show_trash_preview' ] );
		}
	}

	/**
	 * Add a preview link for trashed posts.
	 *
	 * @param $actions
	 * @param $post
	 *
	 * @return mixed
	 */
	public function post_row_actions( $actions, $post ) {
		if ( 'trash' === $post->post_status ) {
			$actions['trash_preview'] = sprintf(
				'<a target="_blank" href="%s">%s</a>',
				esc_url( get_preview_post_link( $post ) ),
				esc_html__( 'Preview', 'textdomain' )
			);
		}

		return $actions;
	}

	/**
	 * Handle a trash preview.
	 *
	 * @param object $query The WP_Query object.
	 *
	 * @return object The WP_Query object, unchanged.
	 */
	public function show_trash_preview( $query ) {
		if (
			$query->is_main_query() &&
			$query->is_preview() &&
			$query->is_singular()
		) {
			add_filter( 'posts_results', [ $this, 'set_trash_to_draft' ], 10, 2 );
		}

		return $query;
	}

	/**
	 * Sets the post status to draft for preview.
	 *
	 * @param array $posts The post to preview.
	 *
	 * @return array Post being previewed.
	 */
	public function set_trash_to_draft( $posts ) {
		remove_filter( 'posts_results', [ $this, 'set_trash_to_draft' ], 10, 2 );
		if ( empty( $posts ) ) {
			return $posts;
		}

		if ( 'trash' !== $posts[0]->post_status ) {
			return $posts;
		}

		$posts[0]->post_status = 'draft';
		return $posts;
	}
}