[stdlib] workaround for CustomPlaygroundQuickLookable in UIView subclasses

Author: Max Moiseev

stdlib/public/SDK/AppKit/AppKit.swift

@@ -13,8 +13,8 @@
 import Foundation
 @_exported import AppKit
 
-extension NSCursor : CustomPlaygroundQuickLookable {
-  public var customPlaygroundQuickLook: PlaygroundQuickLook {
+extension NSCursor : _DefaultCustomPlaygroundQuickLookable {
+  public var _defaultCustomPlaygroundQuickLook: PlaygroundQuickLook {
     return .image(image)
   }
 }
@@ -23,8 +23,8 @@ internal struct _NSViewQuickLookState {
   static var views = Set<NSView>()
 }
 
-extension NSView : CustomPlaygroundQuickLookable {
-  public var customPlaygroundQuickLook: PlaygroundQuickLook {
+extension NSView : _DefaultCustomPlaygroundQuickLookable {
+  public var _defaultCustomPlaygroundQuickLook: PlaygroundQuickLook {
     // if you set NSView.needsDisplay, you can get yourself in a recursive scenario where the same view
     // could need to draw itself in order to get a QLObject for itself, which in turn if your code was
     // instrumented to log on-draw, would cause yourself to get back here and so on and so forth

stdlib/public/SDK/UIKit/UIKit.swift

@@ -187,8 +187,8 @@ internal struct _UIViewQuickLookState {
   static var views = Set<UIView>()
 }
 
-extension UIView : CustomPlaygroundQuickLookable {
-  public var customPlaygroundQuickLook: PlaygroundQuickLook {
+extension UIView : _DefaultCustomPlaygroundQuickLookable {
+  public var _defaultCustomPlaygroundQuickLook: PlaygroundQuickLook {
     if _UIViewQuickLookState.views.contains(self) {
       return .view(UIImage())
     } else {

stdlib/public/core/Mirror.swift

@@ -697,6 +697,9 @@ extension PlaygroundQuickLook {
     if let customized = subject as? CustomPlaygroundQuickLookable {
       self = customized.customPlaygroundQuickLook
     }
+    else if let customized = subject as? _DefaultCustomPlaygroundQuickLookable {
+      self = customized._defaultCustomPlaygroundQuickLook
+    }
     else {
       if let q = _reflect(subject).quickLookObject {
         self = q
@@ -723,6 +726,13 @@ public protocol CustomPlaygroundQuickLookable {
   var customPlaygroundQuickLook: PlaygroundQuickLook { get }
 }
 
+
+// A workaround for <rdar://problem/25971264>
+// FIXME(ABI)
+public protocol _DefaultCustomPlaygroundQuickLookable {
+  var _defaultCustomPlaygroundQuickLook: PlaygroundQuickLook { get }
+}
+
 //===--- General Utilities ------------------------------------------------===//
 // This component could stand alone, but is used in Mirror's public interface.
 

test/1_stdlib/Mirror.swift

@@ -730,6 +730,35 @@ mirrors.test("PlaygroundQuickLook") {
   }
 }
 
+class Parent {}
+
+extension Parent : _DefaultCustomPlaygroundQuickLookable {
+  var _defaultCustomPlaygroundQuickLook: PlaygroundQuickLook {
+    return .text("base")
+  }
+}
+
+class Child : Parent { }
+
+class FancyChild : Parent, CustomPlaygroundQuickLookable {
+  var customPlaygroundQuickLook: PlaygroundQuickLook {
+    return .text("child")
+  }
+}
+
+mirrors.test("_DefaultCustomPlaygroundQuickLookable") {
+  // testing the workaround for custom quicklookables in subclasses
+  switch PlaygroundQuickLook(reflecting: Child()) {
+  case .text("base"): break
+  default: expectUnreachable("Base custom quicklookable was expected")
+  }
+
+  switch PlaygroundQuickLook(reflecting: FancyChild()) {
+  case .text("child"): break
+  default: expectUnreachable("FancyChild custom quicklookable was expected")
+  }
+}
+
 import MirrorObjC
 mirrors.test("ObjC") {
   // Some Foundation classes lie about their ivars, which would crash

test/1_stdlib/UIKit.swift

@@ -78,4 +78,21 @@ UIKitTests.test("UIOffset") {
   checkEquatable(offsets, oracle: { $0 == $1 })
 }
 
+class TestChildView : UIView, CustomPlaygroundQuickLookable {
+  convenience init() {
+    self.init(frame: CGRect(x: 0, y: 0, width: 10, height: 10))
+  }
+  var customPlaygroundQuickLook: PlaygroundQuickLook {
+    return .text("child")
+  }
+}
+
+UIKitTests.test("CustomPlaygroundQuickLookable") {
+  switch PlaygroundQuickLook(reflecting: TestChildView()) {
+  case .text("child"): break
+  default: expectUnreachable(
+    "TestChildView custom quicklookable should have been invoked")
+  }
+}
+
 runAllTests()