wp_ajax_delete_theme()

function wp_ajax_delete_theme() {
	check_ajax_referer( 'updates' );

	if ( empty( $_POST['slug'] ) ) {
		wp_send_json_error( array(
			'slug'         => '',
			'errorCode'    => 'no_theme_specified',
			'errorMessage' => __( 'No theme specified.' ),
		) );
	}

	$stylesheet = preg_replace( '/[^A-z0-9_\-]/', '', wp_unslash( $_POST['slug'] ) );
	$status     = array(
		'delete' => 'theme',
		'slug'   => $stylesheet,
	);

	if ( ! current_user_can( 'delete_themes' ) ) {
		$status['errorMessage'] = __( 'Sorry, you are not allowed to delete themes on this site.' );
		wp_send_json_error( $status );
	}

	if ( ! wp_get_theme( $stylesheet )->exists() ) {
		$status['errorMessage'] = __( 'The requested theme does not exist.' );
		wp_send_json_error( $status );
	}

	// Check filesystem credentials. `delete_theme()` will bail otherwise.
	$url = wp_nonce_url( 'themes.php?action=delete&stylesheet=' . urlencode( $stylesheet ), 'delete-theme_' . $stylesheet );
	ob_start();
	$credentials = request_filesystem_credentials( $url );
	ob_end_clean();
	if ( false === $credentials || ! WP_Filesystem( $credentials ) ) {
		global $wp_filesystem;

		$status['errorCode']    = 'unable_to_connect_to_filesystem';
		$status['errorMessage'] = __( 'Unable to connect to the filesystem. Please confirm your credentials.' );

		// Pass through the error from WP_Filesystem if one was raised.
		if ( $wp_filesystem instanceof WP_Filesystem_Base && is_wp_error( $wp_filesystem->errors ) && $wp_filesystem->errors->get_error_code() ) {
			$status['errorMessage'] = esc_html( $wp_filesystem->errors->get_error_message() );
		}

		wp_send_json_error( $status );
	}

	include_once( ABSPATH . 'wp-admin/includes/theme.php' );

	$result = delete_theme( $stylesheet );

	if ( is_wp_error( $result ) ) {
		$status['errorMessage'] = $result->get_error_message();
		wp_send_json_error( $status );
	} elseif ( false === $result ) {
		$status['errorMessage'] = __( 'Theme could not be deleted.' );
		wp_send_json_error( $status );
	}

	wp_send_json_success( $status );
}