[generator] Add missing `EnsureUIThread` for generated `init` and `initWithCoder` (#8250)

Fix https://github.com/xamarin/xamarin-macios/issues/8249

src/generator.cs

@@ -4184,20 +4184,25 @@ public partial class Generator : IMemberGatherer {
 
 	string CurrentMethod;
 
-	void GenerateThreadCheck ()
+	void GenerateThreadCheck (StreamWriter sw = null)
 	{
+		string s;
 		switch (CurrentPlatform) {
 			case PlatformName.iOS:
 			case PlatformName.WatchOS:
 			case PlatformName.TvOS:
-				print ("global::{0}.UIApplication.EnsureUIThread ();", ns.Get ("UIKit"));
+				s = $"global::{ns.Get ("UIKit")}.UIApplication.EnsureUIThread ();";
 				break;
 			case PlatformName.MacOSX:
-				print ("global::{0}.NSApplication.EnsureUIThread ();", ns.Get ("AppKit"));
+				s = $"global::{ns.Get ("AppKit")}.NSApplication.EnsureUIThread ();";
 				break;
 			default:
 				throw new BindingException (1047, CurrentPlatform);
 		}
+		if (sw == null)
+			print (s);
+		else
+			sw.WriteLine (s);
 	}
 
 	// Stret.NeedStret is shared between generator and X.I dll so in order to wrap the exception
@@ -6451,6 +6456,10 @@ public partial class Generator : IMemberGatherer {
 								sw.WriteLine ("\tthrow new PlatformNotSupportedException (\"This API is not supported on this version of iOS\");");
 								sw.WriteLine ("\t\t#else");
 							}
+							if (type_needs_thread_checks) {
+								sw.Write ("\t\t\t");
+								GenerateThreadCheck (sw);
+							}
 							var indentation = 3;
 							WriteIsDirectBindingCondition (sw, ref indentation, is_direct_binding, is_direct_binding_value,
 							                               () => string.Format ("InitializeHandle (global::{1}.IntPtr_objc_msgSend (this.Handle, global::{2}.{0}), \"init\");", initSelector, ns.Messaging, ns.CoreObjCRuntime),
@@ -6478,7 +6487,10 @@ public partial class Generator : IMemberGatherer {
 							if (nscoding) {
 								if (debug)
 									sw.WriteLine ("\t\t\tConsole.WriteLine (\"{0}.ctor (NSCoder)\");", TypeName);
-								sw.WriteLine ();
+								if (type_needs_thread_checks) {
+									sw.Write ("\t\t\t");
+									GenerateThreadCheck (sw);
+								}
 								var indentation = 3;
 								WriteIsDirectBindingCondition (sw, ref indentation, is_direct_binding, is_direct_binding_value,
 								                               () => string.Format ("InitializeHandle (global::{1}.IntPtr_objc_msgSend_IntPtr (this.Handle, {0}, coder.Handle), \"initWithCoder:\");", initWithCoderSelector, ns.Messaging),

tests/cecil-tests/Helper.cs

@@ -63,8 +63,11 @@ namespace Cecil.Tests {
 				yield return new TestCaseData (Path.Combine (Configuration.MonoTouchRootDirectory, "lib", "32bits", "Xamarin.iOS.dll"));
 				yield return new TestCaseData (Path.Combine (Configuration.MonoTouchRootDirectory, "lib", "64bits", "Xamarin.iOS.dll"));
 
-				yield return new TestCaseData (Configuration.XamarinWatchOSDll);
-				yield return new TestCaseData (Configuration.XamarinTVOSDll);
+				// XamarinWatchOSDll is stripped of its IL
+				yield return new TestCaseData (Path.Combine (Configuration.MonoTouchRootDirectory, "lib", "32bits", "Xamarin.WatchOS.dll"));
+				// XamarinTVOSDll is stripped of it's IL
+				yield return new TestCaseData (Path.Combine (Configuration.MonoTouchRootDirectory, "lib", "64bits", "Xamarin.TVOS.dll"));
+
 				yield return new TestCaseData (Configuration.XamarinMacMobileDll);
 				yield return new TestCaseData (Configuration.XamarinMacFullDll);
 			}

tests/cecil-tests/Test.cs

@@ -48,5 +48,43 @@ namespace Cecil.Tests {
 				}
 			}
 		}
+
+		[TestCaseSource (typeof (Helper), "PlatformAssemblies")]
+		// ref: https://github.com/xamarin/xamarin-macios/issues/8249
+		public void EnsureUIThreadOnInit (string assemblyPath)
+		{
+			var assembly = Helper.GetAssembly (assemblyPath);
+			if (assembly == null) {
+				Assert.Ignore ("{assemblyPath} could not be found (might be disabled in build)");
+				return; // just to help nullability
+			}
+
+			// `CNContactsUserDefaults` is `[ThreadSafe (false)]` and part of iOS and macOS
+			var t = assembly.MainModule.GetType ("Contacts.CNContactsUserDefaults");
+			if (t == null) {
+				// tvOS does not have the type so let's find an alternative
+				t = assembly.MainModule.GetType ("PhotosUI.PHLivePhotoView");
+			}
+			if (t == null) {
+				Assert.Fail ($"No type found for {assembly}");
+				return; // just to help nullability
+			}
+
+			foreach (var c in t.Methods) {
+				if (!c.IsConstructor || c.IsStatic || c.HasParameters)
+					continue;
+				// .ctor(IntPtr)
+				var found = false;
+				foreach (var ins in c.Body.Instructions) {
+					if (ins.OpCode.Code != Code.Call)
+						continue;
+					found |= (ins.Operand as MethodReference)?.Name == "EnsureUIThread";
+				}
+				if (!found)
+					Assert.Fail ("EnsureUIThread missing");
+				else
+					return; // single case, no point in iterating anymore
+			}
+		}
 	}
 }

tests/introspection/Mac/MacApiTypoTest.cs

@@ -12,7 +12,7 @@ namespace Introspection
 	[TestFixture]
 	public class MacApiTypoTest : ApiTypoTest
 	{
-		NSSpellChecker checker = new NSSpellChecker ();
+		NSSpellChecker checker;
 
 		[SetUp]
 		public void SetUp ()
@@ -20,6 +20,7 @@ namespace Introspection
 			var sdk = new Version (Constants.SdkVersion);
 			if (!PlatformHelper.CheckSystemVersion (sdk.Major, sdk.Minor))
 				Assert.Ignore ("Typos only verified using the latest SDK");
+			checker = new NSSpellChecker ();
 		}
 
 		public override string GetTypo (string txt)