Added immutable caching to the fingerprinted media types for the ConfigReader+Properties extension in the Website service target.

Services/Website/Sources/App/Extensions/ConfigReader+Properties.swift

@@ -56,10 +56,15 @@ package extension ConfigReader {
     /// The `Cache-Control` policy applied to static files, grouped by media type.
     ///
     /// The max-ages are read from the `cache.maxAge.asset`, `cache.maxAge.text`, `cache.maxAge.image`, and
-    /// `cache.maxAge.default` keys. Stylesheets and scripts are referenced through fingerprinted URLs (see `FingerprintAssets`) and
+    /// `cache.maxAge.default` keys. Stylesheets, scripts, videos, JPEGs, and WebPs are referenced through fingerprinted URLs (see
-    /// fonts are immutable subset files, so all three are served long-lived and `immutable` — a deploy busts them by changing the URL, never by
+    /// `FingerprintAssets`) and fonts are immutable subset files, so all of them are served long-lived and `immutable` — a deploy busts them by
-    /// revalidation. The remaining text files (e.g. `robots.txt`) keep their unversioned URLs and require revalidation once stale; images and
+    /// changing the URL, never by revalidation. The remaining text files (e.g. `robots.txt`) keep their unversioned URLs and require revalidation
-    /// everything else are served public with their max-age alone. The groups match in order, so the specific types precede the `text` category.
+    /// once stale; the remaining images cannot be `immutable` — the group covers the icons, and a browser fetches `/favicon.ico` unversioned
+    /// whatever the markup says — and everything else is served public with its max-age alone. The groups match in order, so the specific types
+    /// precede the `text` and `image` categories.
+    ///
+    /// - Important: an image the markup references without a `?v=` token must be in neither JPEG nor WebP, or it is served immutable for a year and
+    ///   a deploy cannot dislodge it.
     var cacheControl: CacheControl {
         let maxAgeAsset = int(
             forKey: .Cache.maxAgeAsset,
@@ -82,6 +87,9 @@ package extension ConfigReader {
             (.textCss, [.public, .maxAge(maxAgeAsset), .immutable]),
             (.textJavascript, [.public, .maxAge(maxAgeAsset), .immutable]),
             (.font, [.public, .maxAge(maxAgeAsset), .immutable]),
+            (.videoMp4, [.public, .maxAge(maxAgeAsset), .immutable]),
+            (.imageJpeg, [.public, .maxAge(maxAgeAsset), .immutable]),
+            (.imageWebp, [.public, .maxAge(maxAgeAsset), .immutable]),
             (.text, [.public, .maxAge(maxAgeText), .mustRevalidate]),
             (.image, [.public, .maxAge(maxAgeImage)]),
             (.init(type: .any), [.public, .maxAge(maxAgeDefault)]),

Services/Website/Tests/App/AppTests.swift

@@ -14,10 +14,14 @@ struct AppTests {
 
     // MARK: Constants
 
-    // Stylesheets and scripts are referenced through fingerprinted URLs, so they are served immutable.
+    // Referenced through fingerprinted URLs, or an immutable subset file in the case of a font, so all of these are served immutable.
     private let immutableExtensions: [AssetExtension] = [
         .css,
-        .js
+        .jpg,
+        .js,
+        .mp4,
+        .webp,
+        .woff2
     ]
 
     // Absolute path to the copy of the package's "Resources/Static" folder made into the test bundle

Services/Website/Tests/App/ConfigReaderPropertiesTests.swift

@@ -61,6 +61,44 @@ struct ConfigReaderPropertiesTests {
         #expect(reader(values: [.Analytics.websiteID: ""]).analytics == nil)
     }
 
+    @Test(arguments: [
+        "shared.css",
+        "shared.js",
+        "milker-400.woff2",
+        "booth.mp4",
+        "portrait.jpg",
+        "portrait.webp"
+    ])
+    func `cache control to mark the fingerprinted media immutable`(
+        file: String
+    ) throws {
+        let header = try #require(reader().cacheControl.getCacheControlHeader(for: file))
+
+        #expect(header.contains("immutable"))
+    }
+
+    @Test(arguments: [
+        // The icons are exempt: a browser fetches `/favicon.ico` unversioned whatever the markup says, and the manifest names the PNGs.
+        "favicon.ico",
+        "icon-192.png",
+        "icon.svg"
+    ])
+    func `cache control to leave the unversioned images mutable`(
+        file: String
+    ) throws {
+        let header = try #require(reader().cacheControl.getCacheControlHeader(for: file))
+
+        #expect(!header.contains("immutable"))
+    }
+
+    @Test
+    func `cache control to have the unversioned text revalidate`() throws {
+        let header = try #require(reader().cacheControl.getCacheControlHeader(for: "robots.txt"))
+
+        #expect(header.contains("must-revalidate"))
+        #expect(!header.contains("immutable"))
+    }
+
 }
 
 // MARK: - Helpers