[ios] test MemoryAnalyzers package (#16346)

Context: https://github.com/jonathanpeppers/memory-analyzers
Context: https://www.nuget.org/packages/MemoryAnalyzers/0.1.0-beta.3

This adds a new Roslyn analyzer that warns about the following cases.

 ## MA0001

Don't define `public` events in `NSObject` subclasses:

```csharp
public class MyView : UIView
{
    // NOPE!
    public event EventHandler MyEvent;
}
```

 ## MA0002

Don't declare members in `NSObject` subclasses unless they are:

* `WeakReference` or `WeakReference<T>`
* Value types

```csharp
class MyView : UIView
{
    // NOPE!
    public UIView? Parent { get; set; }

    public void Add(MyView subview)
    {
        subview.Parent = this;
        AddSubview(subview);
    }
}
```

 ## MA0003

Don't subscribe to events inside `NSObject` subclasses unless:

* It's your event via `this.MyEvent` or from a base type.
* The method is `static`.

```csharp
class MyView : UIView
{
    public MyView()
    {
        var picker = new UIDatePicker();
        AddSubview(picker);
        picker.ValueChanged += OnValueChanged;
    }

    void OnValueChanged(object sender, EventArgs e) { }

    // Use this instead and it doesn't leak!
    //static void OnValueChanged(object sender, EventArgs e) { }
}
```

This is also on NuGet, but I just commited the package until we can get
it added to the `dotnet-public` feed.

Places with PRs in flight are marked with:

    [UnconditionalSuppressMessage("Memory", "MA0002", Justification = "FIXME: #16530")]

A few are marked as "not an issue" with an explanation. Others mention a
test with a proof they are OK.

A few places I could actually *remove* `UnconditionalSuppressMessage`
where I could improve the analyzer to ignore that case.

src/Core/src/Core.csproj

@@ -15,6 +15,7 @@
   <Import Project="$(MauiSrcDirectory)MultiTargeting.targets" />
 
   <ItemGroup>
+    <PackageReference Include="MemoryAnalyzers" Version="0.1.0-beta.3" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Extensions.Configuration" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
     <PackageReference Include="Microsoft.Extensions.Logging" />

src/Core/src/Platform/iOS/ContainerViewController.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.Maui.HotReload;
 using ObjCRuntime;
 using UIKit;
@@ -8,11 +9,13 @@ namespace Microsoft.Maui.Platform
 	public class ContainerViewController : UIViewController, IReloadHandler
 	{
 		IElement? _view;
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: NavigationPageTests.DoesNotLeak")]
 		UIView? currentPlatformView;
 
 		// The handler needs this view before LoadView is called on the controller
 		// So this is used to create the first view that the handler will use
 		// without forcing the VC to call LoadView
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: NavigationPageTests.DoesNotLeak")]
 		UIView? _pendingLoadedView;
 
 		public IElement? CurrentView

src/Core/src/Platform/iOS/MauiCheckBox.cs

@@ -27,7 +27,6 @@ public class MauiCheckBox : UIButton
 
 		readonly WeakEventManager _weakEventManager = new WeakEventManager();
 
-		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
 		public event EventHandler? CheckedChanged
 		{
 			add => _weakEventManager.AddEventHandler(value);

src/Core/src/Platform/iOS/MauiRefreshView.cs

@@ -15,11 +15,11 @@ public class MauiRefreshView : UIView
 		bool _isRefreshing;
 		nfloat _originalY;
 		nfloat _refreshControlHeight;
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		UIView _refreshControlParent;
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		UIView? _contentView;
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		UIRefreshControl _refreshControl;
 		public UIRefreshControl RefreshControl => _refreshControl;
 

src/Core/src/Platform/iOS/MauiSearchBar.cs

@@ -1,5 +1,5 @@
 using System;
-using System.ComponentModel.Design;
+using System.Diagnostics.CodeAnalysis;
 using System.Drawing;
 using CoreGraphics;
 using Foundation;
@@ -33,6 +33,7 @@ protected internal MauiSearchBar(NativeHandle handle) : base(handle)
 		// Native Changed doesn't fire when the Text Property is set in code
 		// We use this event as a way to fire changes whenever the Text changes
 		// via code or user interaction.
+		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "FIXME: https://github.com/dotnet/maui/pull/16383")]
 		public event EventHandler<UISearchBarTextChangedEventArgs>? TextSetOrChanged;
 
 		public override string? Text
@@ -51,7 +52,9 @@ public override string? Text
 			}
 		}
 
+		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "FIXME: https://github.com/dotnet/maui/pull/16383")]
 		internal event EventHandler? OnMovedToWindow;
+		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "FIXME: https://github.com/dotnet/maui/pull/16383")]
 		internal event EventHandler? EditingChanged;
 
 		public override void WillMoveToWindow(UIWindow? window)
@@ -74,6 +77,7 @@ public override void WillMoveToWindow(UIWindow? window)
 				OnMovedToWindow?.Invoke(this, EventArgs.Empty);
 		}
 
+		[UnconditionalSuppressMessage("Memory", "MA0003", Justification = "FIXME: https://github.com/dotnet/maui/pull/16383")]
 		void OnEditingChanged(object? sender, EventArgs e)
 		{
 			EditingChanged?.Invoke(this, EventArgs.Empty);

src/Core/src/Platform/iOS/MauiSwipeView.cs

@@ -17,13 +17,13 @@ public class MauiSwipeView : ContentView
 
 		readonly SwipeRecognizerProxy _proxy;
 		readonly Dictionary<ISwipeItem, object> _swipeItems;
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		readonly UITapGestureRecognizer _tapGestureRecognizer;
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		readonly UIPanGestureRecognizer _panGestureRecognizer;
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		UIView _contentView;
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		UIStackView _actionView;
 		SwipeTransitionMode _swipeTransitionMode;
 		SwipeDirection? _swipeDirection;

src/Core/src/Platform/iOS/MauiTextField.cs

@@ -66,9 +66,9 @@ public override UITextRange? SelectedTextRange
 			}
 		}
 
-		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		public event EventHandler? TextPropertySet;
-		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		internal event EventHandler? SelectionChanged;
 	}
 }

src/Core/src/Platform/iOS/MauiTextView.cs

@@ -10,7 +10,7 @@ namespace Microsoft.Maui.Platform
 {
 	public class MauiTextView : UITextView
 	{
-		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		readonly UILabel _placeholderLabel;
 		nfloat? _defaultPlaceholderSize;
 
@@ -38,7 +38,7 @@ public override void WillMoveToWindow(UIWindow? window)
 		// Native Changed doesn't fire when the Text Property is set in code
 		// We use this event as a way to fire changes whenever the Text changes
 		// via code or user interaction.
-		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "Proven safe in test: MemoryTests.DoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MA0001", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		public event EventHandler? TextSetOrChanged;
 
 		public string? PlaceholderText

src/Core/src/Platform/iOS/MauiTimePicker.cs

@@ -7,6 +7,7 @@ namespace Microsoft.Maui.Platform
 {
 	public class MauiTimePicker : NoCaretField
 	{
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		readonly UIDatePicker _picker;
 
 #if !MACCATALYST

src/Core/src/Platform/iOS/MauiUIApplicationDelegate.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Foundation;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui.Hosting;
@@ -158,6 +159,7 @@ public virtual void PerformFetch(UIApplication application, Action<UIBackgroundF
 			Services?.InvokeLifecycleEvents<iOSLifecycle.PerformFetch>(del => del(application, completionHandler));
 		}
 
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "There can only be one MauiUIApplicationDelegate.")]
 		public static MauiUIApplicationDelegate Current { get; private set; } = null!;
 
 		[Export("window")]

src/Core/src/Platform/iOS/MauiWKWebView.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Drawing;
 using System.IO;
 using System.Threading.Tasks;
@@ -12,6 +13,7 @@ namespace Microsoft.Maui.Platform
 {
 	public class MauiWKWebView : WKWebView, IWebViewDelegate
 	{
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Used to persist cookies across WebView instances. Not a leak.")]
 		static WKProcessPool? SharedPool;
 
 		string? _pendingUrl;

src/Core/src/Platform/iOS/PlatformTouchGraphicsView.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Foundation;
 using Microsoft.Maui.Graphics;
 using Microsoft.Maui.Graphics.Platform;
@@ -10,6 +11,7 @@ public class PlatformTouchGraphicsView : PlatformGraphicsView
 	{
 		readonly UIHoverGestureRecognizerProxy _proxy;
 		WeakReference<IGraphicsView>? _graphicsView;
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
 		UIHoverGestureRecognizer? _hoverGesture;
 		RectF _rect;
 		bool _pressedContained = false;

src/Core/src/Platform/iOS/ResignFirstResponderTouchGestureRecognizer.cs

@@ -1,12 +1,15 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using UIKit;
 
 namespace Microsoft.Maui.Platform
 {
 	internal class ResignFirstResponderTouchGestureRecognizer : UITapGestureRecognizer
 	{
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "FIXME: https://github.com/dotnet/maui/pull/16530")]
 		UIView? _targetView;
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "FIXME: https://github.com/dotnet/maui/pull/16530")]
 		Token? _token;
 
 		public ResignFirstResponderTouchGestureRecognizer(UIView targetView) :

src/Core/src/Platform/iOS/WrapperView.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using CoreAnimation;
 using CoreGraphics;
 using Microsoft.Maui.Graphics;
@@ -12,6 +13,7 @@ public partial class WrapperView : UIView, IDisposable
 		CAShapeLayer? _maskLayer;
 		CAShapeLayer? _backgroundMaskLayer;
 		CAShapeLayer? _shadowLayer;
+		[UnconditionalSuppressMessage("Memory", "MA0002", Justification = "_borderView is a SubView")]
 		UIView? _borderView;
 
 		public WrapperView()