Assets and manifests simplification

[thekid]

Current typical code:

// Cache static assets for one week, immutable fingerprinted assets for one year
$manifest= new AssetsManifest($this->environment->path('src/main/webapp/assets/manifest.json'));
$assets= new AssetsFrom($this->environment->path('src/main/webapp'))->with(fn($file) => [
  'Cache-Control' => $manifest->immutable($file) ?? 'max-age=604800, must-revalidate'
]);

Can we simplify the fn($file) => ... boilerplate?

[thekid]

One small improvement would be a caching() method:

$assets= new AssetsFrom($this->environment->path('src/main/webapp'))
  ->caching(fn($path) => $manifest->immutable($path) ?? 'max-age=604800, must-revalidate'))
;

This could go further:

$assets= new AssetsFrom($this->environment->path('src/main/webapp'))
  ->caching($manifest->immutable(...), 'max-age=604800, must-revalidate')
;

---

diff --git a/src/main/php/web/frontend/AssetsFrom.class.php b/src/main/php/web/frontend/AssetsFrom.class.php
index f9c7724..2126cfd 100755
--- a/src/main/php/web/frontend/AssetsFrom.class.php
+++ b/src/main/php/web/frontend/AssetsFrom.class.php
@@ -1,5 +1,6 @@
 <?php namespace web\frontend;
 
+use Closure;
 use io\Path;
 use util\MimeType;
 use web\Handler;
@@ -29,6 +30,7 @@ class AssetsFrom implements Handler {
 
   private $content, $security, $preference;
   private $sources= [];
+  private $caching= [];
 
   /** @param io.Path|io.Folder|string|io.Path[]|io.Folder[]|string[] $sources */
   public function __construct($sources) {
@@ -51,6 +53,17 @@ class AssetsFrom implements Handler {
     return $this;
   }
 
+  /**
+   * Uses caching directives, applying the first to return non-null.
+   *
+   * @param  (string|function(string): string)... $directives
+   * @return self
+   */
+  public function caching(... $directives) {
+    $this->caching= $directives;
+    return $this;
+  }
+
   /** Overwrites security */
   public function enacting(Security $security): self {
     $this->security= $security;
@@ -145,6 +158,12 @@ class AssetsFrom implements Handler {
           foreach ($this->security->headers() as $name => $value) {
             $response->header($name, $value);
           }
+          foreach ($this->caching as $c) {
+            if (null !== $header= ($c instanceof Closure ? $c(basename($path)) : $c)) {
+              $response->header('Cache-Control', $header);
+              break;
+            }
+          }
 
           return $this->content->serve($request, $response, $target->asFile(), $this->mime($path));
         }
diff --git a/src/test/php/web/frontend/unittest/AssetsFromTest.class.php b/src/test/php/web/frontend/unittest/AssetsFromTest.class.php
index 98f3d43..0bc04d3 100755
--- a/src/test/php/web/frontend/unittest/AssetsFromTest.class.php
+++ b/src/test/php/web/frontend/unittest/AssetsFromTest.class.php
@@ -90,6 +90,14 @@ class AssetsFromTest {
     yield ['fixture.rss', 'application/rss+xml; charset='.\xp::ENCODING];
   }
 
+  /** @return iterable */
+  private function caches() {
+    yield [['max-age=604800'], 'max-age=604800'];
+    yield [[fn($path) => 'max-age=604800'], 'max-age=604800'];
+    yield [[fn($path) => null, 'max-age=604800'], 'max-age=604800'];
+    yield [[fn($path) => 'max-age=31536000', 'max-age=604800'], 'max-age=31536000'];
+  }
+
   #[Test]
   public function can_create() {
     new AssetsFrom('.');
@@ -320,6 +328,17 @@ class AssetsFromTest {
     Assert::false(isset($res->headers()['Cache-Control']));
   }
 
+  #[Test, Values(from: 'caches')]
+  public function caching($arguments, $expected) {
+    $files= ['fixture.css' => self::CONTENTS];
+    $res= $this->serve(
+      (new AssetsFrom($this->folderWith($files)))->caching(...$arguments),
+      '/fixture.css'
+    );
+
+    Assert::equals($expected, $res->headers()['Cache-Control']);
+  }
+
   #[After]
   public function cleanup() {
     foreach ($this->remove as $folder) {

[thekid]

Or as an explicit immutable call, which would accept lookup maps with paths as keys:

$assets= new AssetsFrom($this->environment->path('src/main/webapp'))
  ->caching('max-age=604800, must-revalidate'))
  ->immutable($manifest->assets)
;

[thekid]

The question is whether this should be inside web.io.StaticContent

[thekid]

Or something like a dedicated web.io.CacheControl class?

$assets= new AssetsFrom($this->environment->path('src/main/webapp'))
  ->caching(new CacheControl()->options($manifest->immutable(...), 'max-age=604800, must-revalidate'))
;

...ore more verbose

$assets= new AssetsFrom($this->environment->path('src/main/webapp'))
  ->caching(new CacheControl()->default('max-age=604800, must-revalidate')->immutable($manifest->assets))
;

Both would add the possibility to merge with more identitiers

[thekid]

Alternatively, the web.io.CacheControl class could be used like this:

$caching= new CacheControl('max-age=604800, must-revalidate');
$assets= new AssetsFrom($this->environment->path('src/main/webapp'))
  ->caching($caching->immutable($manifest->assets))
;

[thekid]

See also: https://api.ktor.io/ktor-http/io.ktor.http/-cache-control/index.html