From 051cad7972033b1b9c8b9fbea3be1b90c1c23fa9 Mon Sep 17 00:00:00 2001
From: Radek Doulik <radekdoulik@gmail.com>
Date: Mon, 4 Jan 2021 18:29:48 +0100
Subject: [PATCH] [One .NET] Do not preserve IO stream adapter/invoker (#5449)

Context: https://github.com/xamarin/xamarin-android/issues/5167
Context: https://github.com/xamarin/xamarin-android/issues/5206

The following types are accessed through the `CallbackCode` type
in `src/Mono.Android.Export` via System.Reflection:

  * `Android.Runtime.InputStreamAdapter`
  * `Android.Runtime.InputStreamInvoker`
  * `Android.Runtime.OutputStreamAdapter`
  * `Android.Runtime.OutputStreamInvoker`

Historically the use of these types via Reflection required that they
always be preserved, just in case `Mono.Android.Export.dll` was used.

.NET 6 ILLink is able to detect such reflection use.  These types no
longer need to be explicitly preserved in all circumstances.

Stop explicitly preserving these types, and rely on ILLink to
preserve them when `Mono.Android.Export.dll` is used.

This change reduces the `.apk` size in a common situation, when
`Mono.Android.Export.dll` is not used.

apk size comparison, BuildReleaseArm64False test:

	> apkdiff -f -e dll$ before.apk after.apk
	Size difference in bytes ([*1] apk1 only, [*2] apk2 only):
	  -          80 assemblies/System.Console.dll
	  -         129 assemblies/Java.Interop.dll
	  -       1,237 assemblies/System.Private.CoreLib.dll
	  -       6,093 assemblies/Mono.Android.dll
	Summary:
	  -       7,539 Assemblies -1.01% (of 749,078)
---
 .../PreserveLists/Mono.Android.xml                            | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml b/src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml
index 3958d28e331..24c014afc59 100644
--- a/src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml
+++ b/src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml
@@ -5,8 +5,6 @@
 		<type fullname="Android.Runtime.GeneratedDummyHost" />
 		<type fullname="Android.Runtime.GeneratedEnumAttribute" />
 		<type fullname="Android.Runtime.IJavaObject" />
-		<type fullname="Android.Runtime.InputStreamAdapter" />
-		<type fullname="Android.Runtime.InputStreamInvoker" />
 		<type fullname="Android.Runtime.JNIEnv">
 			<method name="Exit" />
 			<method name="Initialize" />
@@ -34,8 +32,6 @@
 		<type fullname="Android.Runtime.LogLevel" />
 		<type fullname="Android.Runtime.LogCategories" />
 		<type fullname="Android.Runtime.NamespaceMappingAttribute" />
-		<type fullname="Android.Runtime.OutputStreamAdapter" />
-		<type fullname="Android.Runtime.OutputStreamInvoker" />
 		<type fullname="Android.Runtime.PreserveAttribute" />
 		<type fullname="Android.Runtime.RaiseThrowableEventArgs" />
 		<type fullname="Android.Runtime.RegisterAttribute" />