Modernization

MIGRATING.md

@@ -0,0 +1,102 @@
+# Migrating to XUI 2.0
+
+XUI 2.0 raises the platform floor, fixes several API quirks that surfaced in long-term use, and modernises the codebase for Swift 5.9+. This guide enumerates every breaking change.
+
+## Platform floor
+
+| | 1.x | 2.0 |
+|---|---|---|
+| iOS | 13.0 | **15.0** |
+| macOS | 10.15 | **12.0** |
+| watchOS | 6.0 | **8.0** |
+| tvOS | 13.0 | **15.0** |
+| Swift tools | 5.3 | **5.9** |
+
+If you cannot raise your deployment target, stay on XUI 1.x.
+
+## `firstReceiver` returns `Receiver?` (was `Receiver!`)
+
+The implicitly-unwrapped optional return type silently produced crashes at unexpected call sites. The signature is now an honest `Receiver?`.
+
+**Before:**
+```swift
+let detail: DetailViewModel = root.firstReceiver(as: DetailViewModel.self)
+detail.open()
+```
+
+**After:**
+```swift
+guard let detail = root.firstReceiver(as: DetailViewModel.self) else { return }
+detail.open()
+```
+
+## `popover(model:)` / `sheet(model:)` argument label
+
+The closure argument label is now `destination:` (was `content:`), matching `navigation(model:)`. The same rename applies to `PopoverModifier` and `SheetModifier`.
+
+**Before:**
+```swift
+.sheet(model: $viewModel.modal, content: { vm in ModalView(viewModel: vm) })
+.popover(model: $viewModel.popover, content: { vm in PopoverView(viewModel: vm) })
+```
+
+**After:**
+```swift
+.sheet(model: $viewModel.modal) { vm in ModalView(viewModel: vm) }
+.popover(model: $viewModel.popover) { vm in PopoverView(viewModel: vm) }
+```
+
+## `sheet(model:)` / `popover(model:)` — value-type model footgun documented
+
+Both modifiers identify the presented item by object identity. Passing a `struct`-typed `Model` silently re-boxes on every render (via `object as AnyObject`), producing a fresh `ObjectIdentifier` each time and causing the sheet/popover to re-present continuously. This was undocumented in 1.x; in 2.0 it's called out in the doc comments.
+
+The constraint was **not** raised to `Model: AnyObject` because doing so would reject `any MyViewModel` even when `MyViewModel: AnyObject` (protocols don't self-conform to `AnyObject`), which would break the protocol-typed view model use case that is XUI's headline feature. The generic stays unconstrained; pass a reference type or a class-constrained protocol existential.
+
+## `navigation(model:)` / `NavigationLink(model:)` / `onNavigation(_:)` / `NavigationModifier` are deprecated
+
+These are built on `NavigationLink(isActive:)`, which Apple deprecated in iOS 16. They still function on iOS 15, but emit a deprecation warning.
+
+**On iOS 16+, replace `.navigation(model:)` with `.navigationDestination(model:)`:**
+
+```swift
+// Before
+ContentView()
+    .navigation(model: $viewModel.detail) { vm in DetailView(viewModel: vm) }
+
+// After
+NavigationStack {
+    ContentView()
+        .navigationDestination(model: $viewModel.detail) { vm in DetailView(viewModel: vm) }
+}
+```
+
+For `NavigationLink(model:destination:label:)`, prefer `NavigationLink(value:)` plus `.navigationDestination(for:)`.
+
+## `Result+Combine` operators are deprecated
+
+`Publisher.asResult()`, `Publisher.mapResult(success:failure:)`, and `Publisher.tryMapResult(...)` are deprecated. They will be removed in a future major release. Prefer structured concurrency:
+
+```swift
+// Before
+publisher.tryMapResult(
+    success: { $0.uppercased() },
+    failure: { _ in "fallback" }
+)
+
+// After
+do {
+    let value = try await asyncCall()
+    return value.uppercased()
+} catch {
+    return "fallback"
+}
+```
+
+## Newly public `Binding.first(equalTo:)` / `Binding.first(as:)`
+
+These overloads were documented in the README but accidentally non-public in 1.x. They are now `public` and available to callers.
+
+## Internal cleanups
+
+- `@_functionBuilder` was migrated to `@resultBuilder` (`CancellableBuilder`, `CollectionBuilder`). Both attributes are functionally equivalent — no caller change required.
+- `Tests/LinuxMain.swift` and `Tests/XUITests/XCTestManifests.swift` were deleted (SwiftPM auto-discovers tests on Linux since 5.4).

Package.swift

@@ -1,10 +1,10 @@
-// swift-tools-version:5.3
+// swift-tools-version: 5.9
 
 import PackageDescription
 
 let package = Package(
     name: "XUI",
-    platforms: [.iOS(.v13), .macOS(.v10_15), .watchOS(.v6), .tvOS(.v13)],
+    platforms: [.iOS(.v15), .macOS(.v12), .watchOS(.v8), .tvOS(.v15)],
     products: [
         .library(
             name: "XUI",