Caching

Alto Importmap does not include a cache layer. Cache the rendered output in the application when rebuilding the same complete map is expensive. Derive the key after every package map and application override has been merged.

<?php

require __DIR__.'/vendor/autoload.php';

use Alto\ImportMap\ImportMap;
use Alto\ImportMap\Renderer\HtmlRenderer;

$map = new ImportMap(imports: ['app' => '/assets/app.js']);
$state = json_encode($map, JSON_THROW_ON_ERROR | JSON_UNESCAPED_SLASHES);
$key = 'importmap.'.hash('sha256', $state);

$cache = [];
$html = $cache[$key] ??= (new HtmlRenderer())->render($map);

echo $key.PHP_EOL;
echo $html;

The key changes when the serialized imports, scopes, integrity metadata, or their order changes. If maps come from files, package manifests, deployment metadata, or environment-specific URLs, include their resulting map state in the key rather than relying only on a fixed cache name.

ImportMap is mutable. Calling add(), addEntry(), or merge() after output has been cached does not invalidate application storage. Finish the map first, then derive the key and render it. Cache import-map HTML and other page output under separate keys when their preload settings differ.