Open same-host non-HTTP(S) URLs (webcal:, mailto:, ...) via the system

Source/Turbo/Navigator/Routing/Handlers/AppNavigationRouteDecisionHandler.swift

@@ -8,6 +8,14 @@ public final class AppNavigationRouteDecisionHandler: RouteDecisionHandler {
     public func matches(proposal: VisitProposal,
                         configuration: Navigator.Configuration) -> Bool {
         let location = proposal.url
+
+        /// Only HTTP(S) URLs can be routed in-app. A same-host URL with a custom
+        /// scheme (e.g. `webcal://my.app.com/calendar.ics`) must fall through to
+        /// `SystemNavigationRouteDecisionHandler` so the system can open it.
+        guard location.scheme == "http" || location.scheme == "https" else {
+            return false
+        }
+
         if #available(iOS 16, *) {
             return configuration.startLocation.host() == location.host()
         }

Source/Turbo/Navigator/Routing/Handlers/SystemNavigationRouteDecisionHandler.swift

@@ -10,6 +10,13 @@ public final class SystemNavigationRouteDecisionHandler: RouteDecisionHandler {
     public func matches(proposal: VisitProposal,
                         configuration: Navigator.Configuration) -> Bool {
         let location = proposal.url
+
+        /// Non-HTTP(S) URLs (webcal:, mailto:, sms:, ...) are always opened via
+        /// the system, even when they point at the app's own host.
+        guard location.scheme == "http" || location.scheme == "https" else {
+            return true
+        }
+
         if #available(iOS 16, *) {
             return configuration.startLocation.host() != location.host()
         }

Tests/Turbo/Routing/AppNavigationRouteDecisionHandlerTest.swift

@@ -38,6 +38,13 @@ final class AppNavigationRouteDecisionHandlerTest: XCTestCase {
         XCTAssertFalse(result)
     }
 
+    func test_non_http_scheme_on_app_domain_does_not_match() {
+        let url = URL(string: "webcal://my.app.com/calendars/subscribe.ics?token=123")!
+        let result = route.matches(proposal: proposal(for: url), configuration: navigatorConfiguration)
+
+        XCTAssertFalse(result)
+    }
+
     func test_masqueraded_url_does_not_match() {
         let url = URL(string: "https://app.my.com@fake.domain")!
         let result = route.matches(proposal: proposal(for: url), configuration: navigatorConfiguration)

Tests/Turbo/Routing/SystemNavigationRouteDecisionHandlerTest.swift

@@ -52,6 +52,13 @@ final class SystemNavigationRouteDecisionHandlerTests: XCTestCase {
         XCTAssertTrue(result)
     }
 
+    func test_non_http_scheme_on_app_domain_matches() {
+        let url = URL(string: "webcal://my.app.com/calendars/subscribe.ics?token=123")!
+        let result = route.matches(proposal: proposal(for: url), configuration: navigatorConfiguration)
+
+        XCTAssertTrue(result)
+    }
+
     func test_sms_urls_match() {
         let url = URL(string: "sms:1-408-555-1212")!
         let result = route.matches(proposal: proposal(for: url), configuration: navigatorConfiguration)