cleanup

Development/Demo/MyBook.swift

@@ -140,6 +140,43 @@ let myBook = Book.init(
     .foregroundStyle(Color.green)
 }
 
+struct StorybookTrait: PreviewModifier {
+  func body(content: Content, context: Void) -> some View {
+    content
+  }
+}
+
+@available(iOS 18.0, *)
+extension PreviewTrait where T == Preview.ViewTraits {
+
+  @MainActor public static var storybook: PreviewTrait<Preview.ViewTraits> {
+    return .init(.modifier(StorybookTrait()))
+  }
+}
+
+struct Storybook: View {
+
+  let content: AnyView
+  init<Content: View>(
+    @ViewBuilder content: () -> Content
+  ) {
+    self.content = .init(content())
+  }
+
+  var body: some View {
+    content
+  }
+}
+
+@available(iOS 18.0, *)
+#Preview(traits: .storybook) {
+  Text("My Component")
+}
+
+#Preview {
+  Text("My Component")
+}
+
 #Preview {
   Text("NO TITLE!")
     .foregroundStyle(Color.purple)
@@ -272,10 +309,10 @@ let myBook = Book.init(
   }
 }
 
-#Preview("Some title 2") {
+#Preview("Title") {
   #StorybookPreview<MyLabel> {
     BookPreview { _ in
-      MyLabel(title: "MyLabel 2")
+      MyLabel(title: "Test")
     }
   }
 }
@@ -284,9 +321,6 @@ let myBook = Book.init(
   BookPreview { _ in
     MyLabel(title: "Test")
   }
-  BookPreview { _ in
-    MyLabel(title: "Test")
-  }
 }
 
 #StorybookPage<MyLabel> {

Development/Demo/RootView.swift

@@ -39,8 +39,10 @@ struct RootView: View {
           }
 
           if #available(iOS 17.0, *) {
-            Book(title: "#Preview macro") {
-              Book.allBookPreviews()
+            if let nodes = Book.allBookPreviews() {
+              Book(title: "#Preview macro") {
+                nodes
+              }
             }
           }
         }

Sources/StorybookKit/Internals/Preview/PreviewRegistryWrapper.swift

@@ -0,0 +1,203 @@
+import DeveloperToolsSupport
+import Foundation
+import SwiftUI
+import UIKit
+
+@available(iOS 17.0, *)
+struct PreviewRegistryWrapper: Comparable {
+
+  let previewType: any DeveloperToolsSupport.PreviewRegistry.Type
+  let module: String
+
+  init(_ previewType: any DeveloperToolsSupport.PreviewRegistry.Type) {
+    self.previewType = previewType
+    self.module = previewType.fileID.components(separatedBy: "/").first!
+  }
+
+  var fileID: String { previewType.fileID }
+  var line: Int { previewType.line }
+  var column: Int { previewType.column }
+
+  @MainActor
+  var makeView: (@MainActor () -> any View) {
+    let preview: FieldReader = .init(try! previewType.makePreview())
+    let title: String? = preview["displayName"]
+    let source: FieldReader = preview["source"]
+    switch source.typeName {
+
+    case "SwiftUI.ViewPreviewSource": // iOS 17
+      let makeView: MakeFunctionWrapper<any SwiftUI.View> = .init(source["makeView"])
+      return {
+        VStack {
+          if let title, !title.isEmpty {
+            Text(title)
+              .font(.system(size: 17, weight: .semibold))
+          }
+          AnyView(makeView())
+          Text("\(fileID):\(line)")
+            .font(.caption.monospacedDigit())
+          BookSpacer(height: 16)
+        }
+      }
+
+    case "UIKit.UIViewPreviewSource": // iOS 17
+      // Unsupported due to iOS 17 not supporting casting between non-sendable closure types
+      return {
+        VStack {
+          if let title, !title.isEmpty {
+            Text(title)
+              .font(.system(size: 17, weight: .semibold))
+          }
+          Text("\(fileID):\(line)")
+            .font(.caption.monospacedDigit())
+          Text("UIView Preview not supported (UIKit.UIViewPreviewSource)")
+            .foregroundStyle(Color.red)
+            .font(.caption.monospacedDigit())
+          BookSpacer(height: 16)
+        }
+      }
+
+    case "DeveloperToolsSupport.DefaultPreviewSource<SwiftUI.ViewPreviewBody>": // iOS 18
+      let makeBody: MakeFunctionWrapper<any SwiftUI.View> = .init(source["structure", "singlePreview", "makeBody"])
+      return {
+        VStack {
+          if let title, !title.isEmpty {
+            Text(title)
+              .font(.system(size: 17, weight: .semibold))
+          }
+          AnyView(makeBody())
+          Text("\(fileID):\(line)")
+            .font(.caption.monospacedDigit())
+          BookSpacer(height: 16)
+        }
+      }
+
+    case "DeveloperToolsSupport.DefaultPreviewSource<__C.UIView>": // iOS 18
+      let makeBody: MakeFunctionWrapper<UIView> = .init(source["structure", "singlePreview", "makeBody"])
+      return {
+        BookPreview(
+          fileID,
+          line,
+          title: title ?? source.typeName,
+          viewBlock: { _ in
+            makeBody()
+          }
+        )
+      }
+
+    case "DeveloperToolsSupport.DefaultPreviewSource<__C.UIViewController>": // iOS 18
+      let makeBody: MakeFunctionWrapper<UIViewController> = .init(source["structure", "singlePreview", "makeBody"])
+      return {
+        BookPresent(
+          title: title ?? source.typeName,
+          presentingViewControllerBlock: {
+            makeBody()
+          }
+        )
+      }
+
+    case let sourceTypeName:
+      return {
+        VStack {
+          if let title, !title.isEmpty {
+            Text(title)
+              .font(.system(size: 17, weight: .semibold))
+          }
+          Text("\(fileID):\(line)")
+            .font(.caption.monospacedDigit())
+          Text("Failed to load preview (\(sourceTypeName))")
+            .foregroundStyle(Color.red)
+            .font(.caption.monospacedDigit())
+          BookSpacer(height: 16)
+        }
+      }
+    }
+  }
+
+
+  // MARK: Comparable
+
+  static func < (lhs: PreviewRegistryWrapper, rhs: PreviewRegistryWrapper) -> Bool {
+    if lhs.module == rhs.module {
+      return lhs.line < rhs.line
+    }
+    return lhs.module < rhs.module
+  }
+
+
+  // MARK: Equatable
+
+  static func == (lhs: PreviewRegistryWrapper, rhs: PreviewRegistryWrapper) -> Bool {
+    lhs.line == rhs.line && lhs.module == rhs.module
+  }
+
+
+  // MARK: - FieldReader
+
+  private struct FieldReader {
+
+    let instance: Any
+    let typeName: String
+
+    init(_ instance: Any) {
+      self.instance = instance
+      self.typeName = String(reflecting: type(of: instance))
+      let mirror: Mirror = .init(reflecting: instance)
+      self.fields = .init(
+        uniqueKeysWithValues: mirror.children.compactMap { (label, value) in
+          label.map({ ($0, value) })
+        }
+      )
+    }
+
+    subscript<T>(_ key: String, _ nextKeys: String...) -> T {
+      if nextKeys.isEmpty {
+        return fields[key] as! T
+      }
+      else {
+        return Self.traverse(from: fields[key]!, nextKeys: nextKeys) as! T
+      }
+    }
+
+    subscript(_ key: String, _ nextKeys: String...) -> FieldReader {
+      .init(Self.traverse(from: fields[key]!, nextKeys: nextKeys))
+    }
+
+    private let fields: [String: Any]
+
+    private static func traverse<C: Collection<String>>(from first: Any, nextKeys: C) -> Any {
+      if let key = nextKeys.first {
+        let mirror: Mirror = .init(reflecting: first)
+        return self.traverse(
+          from: mirror.children.first(where: { $0.label == key })!.value,
+          nextKeys: nextKeys.dropFirst()
+        )
+      }
+      else {
+        return first
+      }
+    }
+  }
+
+
+  // MARK: - MakeFunctionWrapper
+
+  @MainActor
+  private struct MakeFunctionWrapper<T> {
+
+    typealias Closure = @MainActor () -> T
+    private let closure: Closure
+
+    init(_ closure: Any) {
+      // TODO: We need a workaround to avoid implicit @Sendable from @MainActor closures
+      self.closure = unsafeBitCast(
+        closure,
+        to: Closure.self
+      )
+    }
+
+    func callAsFunction() -> T {
+      closure()
+    }
+  }
+}