feat(native): Swift Item draws core's row with typed slots, as a link or a button

packages/native/apple/README.md

@@ -28,6 +28,7 @@ apple/
 │   │   ├── Localization/
 │   │   ├── Icon/          # Icon
 │   │   ├── Avatar/        # Avatar
+│   │   ├── Item/          # Item
 │   │   ├── Text/          # Text
 │   │   ├── Heading/       # Heading
 │   │   ├── Button/        # Button

packages/native/apple/Sources/Astryx/Avatar/Avatar.swift

@@ -77,10 +77,7 @@ public struct Avatar<Status: View>: View {
   /// the build with its value, and an unnamed link or button is flagged.
   private func checkInDevelopment() {
     #if DEBUG
-    if Avatar.isUnusableHref(props.href) {
-      assertionFailure(
-        "Avatar href \"\(props.href ?? "")\" is not an absolute URL an app can open; it draws without a link.")
-    }
+    astryxCheckHref(props.href, in: "Avatar")
     // The avatar's own name: a status label alone does not name a person.
     let ownName = Avatar.meaningful(props.alt) ?? Avatar.meaningful(props.name)
     if Avatar.needsNameWarning(tap: tap, isNamed: ownName != nil) {
@@ -108,11 +105,7 @@ public struct Avatar<Status: View>: View {
   }
 
   /// A non-empty `href` that is not an absolute URL, such as a web path.
-  nonisolated static func isUnusableHref(_ href: String?) -> Bool {
-    guard let href, !href.isEmpty else { return false }
-    guard let url = URL(string: href) else { return true }
-    return url.scheme == nil
-  }
+  nonisolated static func isUnusableHref(_ href: String?) -> Bool { astryxIsUnusableHref(href) }
 
   /// The picture as a link with `href`, a button with only `onClick`, or a
   /// static image (Swift component API, A4). All three draw the same.

packages/native/apple/Sources/Astryx/Base/SafeDestination.swift

@@ -0,0 +1,48 @@
+// Copyright (c) Meta Platforms, Inc. and affiliates.
+
+import Foundation
+
+/// An `href` as a link reads it: control characters removed and surrounding
+/// whitespace trimmed, as core's shared destination rule does.
+func astryxNormalizedHref(_ href: String) -> String {
+  String(String.UnicodeScalarView(
+    href.unicodeScalars.filter { $0.value > 0x1F && $0.value != 0x7F }
+  )).trimmingCharacters(in: .whitespacesAndNewlines)
+}
+
+/// A destination a link may open, normalized as core's shared rule does, or
+/// nil for a script URL or an HTML document in a `data:` URL, which core's
+/// navigation destinations refuse (`family:navigation-destinations` FR4).
+/// The scheme is compared in lowercase without the spaces after its colon,
+/// which a data URL's media type ignores (`data: text/html` is HTML).
+func astryxSafeDestination(_ href: String) -> String? {
+  let normalized = astryxNormalizedHref(href)
+  var comparable = normalized.lowercased()
+  if let colon = comparable.firstIndex(of: ":"),
+     comparable[..<colon].range(of: "^[a-z][a-z0-9+.-]*$", options: .regularExpression) != nil {
+    let rest = comparable[comparable.index(after: colon)...].drop { $0 == " " }
+    comparable = String(comparable[...colon]) + rest
+  }
+  for blocked in ["javascript:", "vbscript:", "data:text/html"] where comparable.hasPrefix(blocked) {
+    return nil
+  }
+  return normalized
+}
+
+/// A non-empty `href` that is not an absolute URL, such as a web path. Pass
+/// the `href` as the view's link reads it, so the check and the link agree.
+func astryxIsUnusableHref(_ href: String?) -> Bool {
+  guard let href, !href.isEmpty else { return false }
+  guard let url = URL(string: href) else { return true }
+  return url.scheme == nil
+}
+
+/// Stops a development build on an `href` an app cannot open, naming the
+/// component and the value; a release build draws the view without a link.
+func astryxCheckHref(_ href: String?, in component: String) {
+  #if DEBUG
+  if astryxIsUnusableHref(href) {
+    assertionFailure("\(component) href \"\(href ?? "")\" is not an absolute URL an app can open; it draws without a link.")
+  }
+  #endif
+}

packages/native/apple/Sources/Astryx/Button/Button.swift

@@ -82,27 +82,9 @@ public struct Button: View {
   /// disabled button, as core draws a disabled `<button>`.
   var link: URL? { isDisabled ? nil : destination }
 
-  /// A destination a link may open, normalized as core's shared rule does, or
-  /// nil for a script URL or an HTML document in a `data:` URL, which core's
-  /// navigation destinations refuse (`family:navigation-destinations` FR4).
-  /// Control characters are removed and whitespace trimmed; the scheme is
-  /// compared in lowercase without the spaces after its colon, which a data
-  /// URL's media type ignores (`data: text/html` is HTML).
-  nonisolated static func safeDestination(_ href: String) -> String? {
-    let normalized = String(String.UnicodeScalarView(
-      href.unicodeScalars.filter { $0.value > 0x1F && $0.value != 0x7F }
-    )).trimmingCharacters(in: .whitespacesAndNewlines)
-    var comparable = normalized.lowercased()
-    if let colon = comparable.firstIndex(of: ":"),
-       comparable[..<colon].range(of: "^[a-z][a-z0-9+.-]*$", options: .regularExpression) != nil {
-      let rest = comparable[comparable.index(after: colon)...].drop { $0 == " " }
-      comparable = String(comparable[...colon]) + rest
-    }
-    for blocked in ["javascript:", "vbscript:", "data:text/html"] where comparable.hasPrefix(blocked) {
-      return nil
-    }
-    return normalized
-  }
+  /// A destination a link may open, or nil when core's navigation
+  /// destinations refuse it (`astryxSafeDestination`).
+  nonisolated static func safeDestination(_ href: String) -> String? { astryxSafeDestination(href) }
 
   public var body: some View {
     control