[Mono.Android] Interfaces contain nested types in API-30+ (#4363)

Context: dotnet/java-interop#509
Context: https://gist.github.com/jpobst/a23ecebbed0837a1abfe7c6cbd7ecf1e

Use `generator --lang-features=nested-interface-types` so that we
start binding Java types nested within interfaces in a similar
fashion in C#.  For example:

	// Java
	package android.view;
	public /* partial */ interface WindowInsetsAnimationCallback {
	    public /* partial */ class AnimationBounds {
	    }
	}

Will be bound as:

	// C#
	namespace Android.Views {
	    public partial interface IWindowInsetsAnimationCallback {
	        public partial class AnimationBounds {
		}
	    }
	}

This new binding approach will only be done for types added in API-R.
We can't do this for any previous bindings, as this would break API.
This is done via `metadata` that looks for all `@merge.SourceFile`
values prior to API-30 and adds the `//@unnest=true` attribute to those
types.  This attribute tells `generator` to treat them as legacy
"unnested" types for backwards compatibility.

The v10.0.99/API-R API diff between 54beb90 and this change:

	--- 54beb90.cs	2020-03-06 11:19:47.000000000 -0500
	+++ nested.cs	2020-03-06 11:19:19.000000000 -0500
	@@ -134296,13 +134296,43 @@
	     {
	         int DispatchMode { [Android.Runtime.RegisterAttribute("getDispatchMode", "()I", "GetGetDispatchModeHandler:Android.Views.IWindowInsetsAnimationCallbackInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")] get; }
	         [Android.Runtime.RegisterAttribute("onFinish", "(Landroid/view/WindowInsetsAnimationCallback$InsetsAnimation;)V", "GetOnFinish_Landroid_view_WindowInsetsAnimationCallback_InsetsAnimation_Handler:Android.Views.IWindowInsetsAnimationCallback, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")]
	-        void OnFinish(Android.Views.WindowInsetsAnimationCallbackInsetsAnimation animation) { }
	+        void OnFinish(Android.Views.IWindowInsetsAnimationCallback.InsetsAnimation animation) { }
	         [Android.Runtime.RegisterAttribute("onPrepare", "(Landroid/view/WindowInsetsAnimationCallback$InsetsAnimation;)V", "GetOnPrepare_Landroid_view_WindowInsetsAnimationCallback_InsetsAnimation_Handler:Android.Views.IWindowInsetsAnimationCallback, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")]
	-        void OnPrepare(Android.Views.WindowInsetsAnimationCallbackInsetsAnimation animation) { }
	+        void OnPrepare(Android.Views.IWindowInsetsAnimationCallback.InsetsAnimation animation) { }
	         [Android.Runtime.RegisterAttribute("onProgress", "(Landroid/view/WindowInsets;)Landroid/view/WindowInsets;", "GetOnProgress_Landroid_view_WindowInsets_Handler:Android.Views.IWindowInsetsAnimationCallbackInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")]
	         Android.Views.WindowInsets OnProgress(Android.Views.WindowInsets insets);
	         [Android.Runtime.RegisterAttribute("onStart", "(Landroid/view/WindowInsetsAnimationCallback$InsetsAnimation;Landroid/view/WindowInsetsAnimationCallback$AnimationBounds;)Landroid/view/WindowInsetsAnimationCallback$AnimationBounds;", "GetOnStart_Landroid_view_WindowInsetsAnimationCallback_InsetsAnimation_Landroid_view_WindowInsetsAnimationCallback_AnimationBounds_Handler:Android.Views.IWindowInsetsAnimationCallback, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")]
	-        Android.Views.WindowInsetsAnimationCallbackAnimationBounds OnStart(Android.Views.WindowInsetsAnimationCallbackInsetsAnimation animation, Android.Views.WindowInsetsAnimationCallbackAnimationBounds bounds) { throw null; }
	+        Android.Views.IWindowInsetsAnimationCallback.AnimationBounds OnStart(Android.Views.IWindowInsetsAnimationCallback.InsetsAnimation animation, Android.Views.IWindowInsetsAnimationCallback.AnimationBounds bounds) { throw null; }
	+        [Android.Runtime.RegisterAttribute("android/view/WindowInsetsAnimationCallback$AnimationBounds", DoNotGenerateAcw=true)]
	+        public sealed partial class AnimationBounds : Java.Lang.Object
	+        {
	+            [Android.Runtime.RegisterAttribute(".ctor", "(Landroid/graphics/Insets;Landroid/graphics/Insets;)V", "")]
	+            public AnimationBounds(Android.Graphics.Insets lowerBound, Android.Graphics.Insets upperBound) { }
	+            public override Java.Interop.JniPeerMembers JniPeerMembers { get { throw null; } }
	+            public Android.Graphics.Insets LowerBound { [Android.Runtime.RegisterAttribute("getLowerBound", "()Landroid/graphics/Insets;", "")] get { throw null; } }
	+            protected override System.IntPtr ThresholdClass { get { throw null; } }
	+            protected override System.Type ThresholdType { get { throw null; } }
	+            public Android.Graphics.Insets UpperBound { [Android.Runtime.RegisterAttribute("getUpperBound", "()Landroid/graphics/Insets;", "")] get { throw null; } }
	+            [Android.Runtime.RegisterAttribute("inset", "(Landroid/graphics/Insets;)Landroid/view/WindowInsetsAnimationCallback$AnimationBounds;", "")]
	+            public Android.Views.IWindowInsetsAnimationCallback.AnimationBounds Inset(Android.Graphics.Insets insets) { throw null; }
	+        }
	+        [Android.Runtime.RegisterAttribute("android/view/WindowInsetsAnimationCallback$InsetsAnimation", DoNotGenerateAcw=true)]
	+        public sealed partial class InsetsAnimation : Java.Lang.Object
	+        {
	+            [Android.Runtime.RegisterAttribute(".ctor", "(ILandroid/view/animation/Interpolator;J)V", "")]
	+            public InsetsAnimation(int typeMask, Android.Views.Animations.IInterpolator interpolator, long durationMs) { }
	+            public float Alpha { [Android.Runtime.RegisterAttribute("getAlpha", "()F", "")] get { throw null; } }
	+            public long DurationMillis { [Android.Runtime.RegisterAttribute("getDurationMillis", "()J", "")] get { throw null; } }
	+            public float Fraction { [Android.Runtime.RegisterAttribute("getFraction", "()F", "")] get { throw null; } [Android.Runtime.RegisterAttribute("setFraction", "(F)V", "")] set { } }
	+            public float InterpolatedFraction { [Android.Runtime.RegisterAttribute("getInterpolatedFraction", "()F", "")] get { throw null; } }
	+            public Android.Views.Animations.IInterpolator Interpolator { [Android.Runtime.RegisterAttribute("getInterpolator", "()Landroid/view/animation/Interpolator;", "")] get { throw null; } }
	+            public override Java.Interop.JniPeerMembers JniPeerMembers { get { throw null; } }
	+            protected override System.IntPtr ThresholdClass { get { throw null; } }
	+            protected override System.Type ThresholdType { get { throw null; } }
	+            public int TypeMask { [Android.Runtime.RegisterAttribute("getTypeMask", "()I", "")] get { throw null; } }
	+            [Android.Runtime.RegisterAttribute("setDuration", "(J)V", "")]
	+            public void SetDuration(long durationMs) { }
	+        }
	     }
	     [Android.Runtime.RegisterAttribute("android/view/WindowInsetsAnimationController", "", "Android.Views.IWindowInsetsAnimationControllerInvoker")]
	     public partial interface IWindowInsetsAnimationController : Android.Runtime.IJavaObject, Java.Interop.IJavaPeerable, System.IDisposable
	@@ -137605,13 +137635,13 @@
	         [Android.Runtime.RegisterAttribute("dispatchWindowFocusChanged", "(Z)V", "GetDispatchWindowFocusChanged_ZHandler")]
	         public virtual void DispatchWindowFocusChanged(bool hasFocus) { }
	         [Android.Runtime.RegisterAttribute("dispatchWindowInsetsAnimationFinish", "(Landroid/view/WindowInsetsAnimationCallback$InsetsAnimation;)V", "GetDispatchWindowInsetsAnimationFinish_Landroid_view_WindowInsetsAnimationCallback_InsetsAnimation_Handler")]
	-        public virtual void DispatchWindowInsetsAnimationFinish(Android.Views.WindowInsetsAnimationCallbackInsetsAnimation animation) { }
	+        public virtual void DispatchWindowInsetsAnimationFinish(Android.Views.IWindowInsetsAnimationCallback.InsetsAnimation animation) { }
	         [Android.Runtime.RegisterAttribute("dispatchWindowInsetsAnimationPrepare", "(Landroid/view/WindowInsetsAnimationCallback$InsetsAnimation;)V", "GetDispatchWindowInsetsAnimationPrepare_Landroid_view_WindowInsetsAnimationCallback_InsetsAnimation_Handler")]
	-        public virtual void DispatchWindowInsetsAnimationPrepare(Android.Views.WindowInsetsAnimationCallbackInsetsAnimation animation) { }
	+        public virtual void DispatchWindowInsetsAnimationPrepare(Android.Views.IWindowInsetsAnimationCallback.InsetsAnimation animation) { }
	         [Android.Runtime.RegisterAttribute("dispatchWindowInsetsAnimationProgress", "(Landroid/view/WindowInsets;)Landroid/view/WindowInsets;", "GetDispatchWindowInsetsAnimationProgress_Landroid_view_WindowInsets_Handler")]
	         public virtual Android.Views.WindowInsets DispatchWindowInsetsAnimationProgress(Android.Views.WindowInsets insets) { throw null; }
	         [Android.Runtime.RegisterAttribute("dispatchWindowInsetsAnimationStart", "(Landroid/view/WindowInsetsAnimationCallback$InsetsAnimation;Landroid/view/WindowInsetsAnimationCallback$AnimationBounds;)Landroid/view/WindowInsetsAnimationCallback$AnimationBounds;", "GetDispatchWindowInsetsAnimationStart_Landroid_view_WindowInsetsAnimationCallback_InsetsAnimation_Landroid_view_WindowInsetsAnimationCallback_AnimationBounds_Handler")]
	-        public virtual Android.Views.WindowInsetsAnimationCallbackAnimationBounds DispatchWindowInsetsAnimationStart(Android.Views.WindowInsetsAnimationCallbackInsetsAnimation animation, Android.Views.WindowInsetsAnimationCallbackAnimationBounds bounds) { throw null; }
	+        public virtual Android.Views.IWindowInsetsAnimationCallback.AnimationBounds DispatchWindowInsetsAnimationStart(Android.Views.IWindowInsetsAnimationCallback.InsetsAnimation animation, Android.Views.IWindowInsetsAnimationCallback.AnimationBounds bounds) { throw null; }
	         [Android.Runtime.RegisterAttribute("dispatchWindowSystemUiVisiblityChanged", "(I)V", "GetDispatchWindowSystemUiVisiblityChanged_IHandler", ApiSince=16)]
	         public virtual void DispatchWindowSystemUiVisiblityChanged([Android.Runtime.GeneratedEnumAttribute] Android.Views.SystemUiFlags visible) { }
	         [Android.Runtime.RegisterAttribute("dispatchWindowVisibilityChanged", "(I)V", "GetDispatchWindowVisibilityChanged_IHandler")]
	@@ -139966,42 +139996,12 @@
	         [Android.Runtime.RegisterAttribute("DISPATCH_MODE_STOP")]
	         public const int DispatchModeStop = 0;
	     }
	-    [Android.Runtime.RegisterAttribute("android/view/WindowInsetsAnimationCallback$AnimationBounds", DoNotGenerateAcw=true)]
	-    public sealed partial class WindowInsetsAnimationCallbackAnimationBounds : Java.Lang.Object
	-    {
	-        [Android.Runtime.RegisterAttribute(".ctor", "(Landroid/graphics/Insets;Landroid/graphics/Insets;)V", "")]
	-        public WindowInsetsAnimationCallbackAnimationBounds(Android.Graphics.Insets lowerBound, Android.Graphics.Insets upperBound) { }
	-        public override Java.Interop.JniPeerMembers JniPeerMembers { get { throw null; } }
	-        public Android.Graphics.Insets LowerBound { [Android.Runtime.RegisterAttribute("getLowerBound", "()Landroid/graphics/Insets;", "")] get { throw null; } }
	-        protected override System.IntPtr ThresholdClass { get { throw null; } }
	-        protected override System.Type ThresholdType { get { throw null; } }
	-        public Android.Graphics.Insets UpperBound { [Android.Runtime.RegisterAttribute("getUpperBound", "()Landroid/graphics/Insets;", "")] get { throw null; } }
	-        [Android.Runtime.RegisterAttribute("inset", "(Landroid/graphics/Insets;)Landroid/view/WindowInsetsAnimationCallback$AnimationBounds;", "")]
	-        public Android.Views.WindowInsetsAnimationCallbackAnimationBounds Inset(Android.Graphics.Insets insets) { throw null; }
	-    }
	     [Android.Runtime.RegisterAttribute("android/view/WindowInsetsAnimationCallback", DoNotGenerateAcw=true)]
	     [System.ObsoleteAttribute("Use the 'WindowInsetsAnimationCallback' type. This type will be removed in a future release.", true)]
	     public abstract partial class WindowInsetsAnimationCallbackConsts : Android.Views.WindowInsetsAnimationCallback
	     {
	         internal WindowInsetsAnimationCallbackConsts() { }
	     }
	-    [Android.Runtime.RegisterAttribute("android/view/WindowInsetsAnimationCallback$InsetsAnimation", DoNotGenerateAcw=true)]
	-    public sealed partial class WindowInsetsAnimationCallbackInsetsAnimation : Java.Lang.Object
	-    {
	-        [Android.Runtime.RegisterAttribute(".ctor", "(ILandroid/view/animation/Interpolator;J)V", "")]
	-        public WindowInsetsAnimationCallbackInsetsAnimation(int typeMask, Android.Views.Animations.IInterpolator interpolator, long durationMs) { }
	-        public float Alpha { [Android.Runtime.RegisterAttribute("getAlpha", "()F", "")] get { throw null; } }
	-        public long DurationMillis { [Android.Runtime.RegisterAttribute("getDurationMillis", "()J", "")] get { throw null; } }
	-        public float Fraction { [Android.Runtime.RegisterAttribute("getFraction", "()F", "")] get { throw null; } [Android.Runtime.RegisterAttribute("setFraction", "(F)V", "")] set { } }
	-        public float InterpolatedFraction { [Android.Runtime.RegisterAttribute("getInterpolatedFraction", "()F", "")] get { throw null; } }
	-        public Android.Views.Animations.IInterpolator Interpolator { [Android.Runtime.RegisterAttribute("getInterpolator", "()Landroid/view/animation/Interpolator;", "")] get { throw null; } }
	-        public override Java.Interop.JniPeerMembers JniPeerMembers { get { throw null; } }
	-        protected override System.IntPtr ThresholdClass { get { throw null; } }
	-        protected override System.Type ThresholdType { get { throw null; } }
	-        public int TypeMask { [Android.Runtime.RegisterAttribute("getTypeMask", "()I", "")] get { throw null; } }
	-        [Android.Runtime.RegisterAttribute("setDuration", "(J)V", "")]
	-        public void SetDuration(long durationMs) { }
	-    }
	     [Android.Runtime.RegisterAttribute("android/view/WindowInsetsController", DoNotGenerateAcw=true)]
	     public abstract partial class WindowInsetsController : Java.Lang.Object
	     {

Author: jpobst

src/Mono.Android/Mono.Android.targets

@@ -98,7 +98,7 @@
       <_Api>$(IntermediateOutputPath)mcw\api.xml</_Api>
       <_Dirs>--enumdir=$(IntermediateOutputPath)mcw</_Dirs>
       <_FullIntermediateOutputPath>$([System.IO.Path]::GetFullPath('$(IntermediateOutputPath)'))</_FullIntermediateOutputPath>
-      <_LangFeatures Condition="$(AndroidApiLevel) &gt;= 30">--lang-features=default-interface-methods</_LangFeatures>
+      <_LangFeatures Condition="$(AndroidApiLevel) &gt;= 30">--lang-features=default-interface-methods,nested-interface-types</_LangFeatures>
     </PropertyGroup>
     <Exec
         Command="$(ManagedRuntime) $(ManagedRuntimeArgs) $(Generator) $(_GenFlags) $(_ApiLevel) $(_Out) $(_Codegen) $(_Fixup) $(_Enums1) $(_Enums2) $(_Versions) $(_Annotations) $(_Assembly) $(_TypeMap) $(_LangFeatures) $(_Dirs) $(_Api)"

src/Mono.Android/metadata

@@ -1560,4 +1560,44 @@
   <remove-node api-since="30" path="/api/package[@name='android.animation']/interface[@name='Animator.AnimatorListener']/method[@name='onAnimationStart' and count(parameter)=2]" />
   <remove-node api-since="30" path="/api/package[@name='android.animation']/interface[@name='Animator.AnimatorListener']/method[@name='onAnimationEnd' and count(parameter)=2]" />
 
+  <!-- Starting with API added in API-30, we are going to allow interfaces to contain nested types.
+       To preserve backwards compatibility, we need to "un-nest" anything added before API-30 -->
+  
+  <!-- Handle everything that has always existed (no @merge.SourceFile) -->
+  <attr api-since="30" path="/api/package/interface[not(@merge.SourceFile)]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[not(@merge.SourceFile)]" name="unnest">true</attr>
+
+  <!-- Need these for each platform prior to 30 -->
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-10.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-10.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-15.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-15.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-16.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-16.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-17.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-17.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-18.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-18.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-19.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-19.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-20.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-20.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-21.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-21.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-22.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-22.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-23.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-23.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-24.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-24.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-25.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-25.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-26.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-26.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-27.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-27.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-28.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-28.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/interface[contains(@merge.SourceFile,'api-29.xml.in')]" name="unnest">true</attr>
+  <attr api-since="30" path="/api/package/class[contains(@merge.SourceFile,'api-29.xml.in')]" name="unnest">true</attr>
 </metadata>