[One .NET] "greenfield" projects opt into trimming

This is WIP depends on dotnet#8778.

As we have solved all trimming warnings in the Android workload, we
can now go "all in" on trimming.

Early in .NET 6 (maybe even 5?) we "hid" many trimming warnings as we
did not yet plan to solve them:

    <SuppressTrimAnalysisWarnings Condition=" '$(SuppressTrimAnalysisWarnings)' == '' ">true</SuppressTrimAnalysisWarnings>

These warnings were not *actionable* at the time for customers, as
many warnings were in `Mono.Android.dll`, `Java.Interop.dll`, etc.

Going forward, let's stop suppressing these warnings if `TrimMode=full`.

We can also enable trimming for new projects:

* `dotnet new android`
* `dotnet new android-wear`

These will have the `TrimMode` property set to `Full` by default:

    <!--
      Enable full trimming in Release mode.
      To learn more, see: https://learn.microsoft.com/dotnet/core/deploying/trimming/trimming-options#trimming-granularity
    -->
    <PropertyGroup Condition="'$(Configuration)' == 'Release'">
      <TrimMode>full</TrimMode>
    </PropertyGroup>

We wouldn't want to do this for existing projects *yet*, as they might
have existing code, NuGet packages, etc. where trimming warnings might
be present.

We can also improve the templates for Android class libraries:

* `dotnet new androidlib`
* `dotnet new android-bindinglib`

    <!--
      Enable trim analyzers for Android class libraries.
      To learn more, see: https://learn.microsoft.com/dotnet/core/deploying/trimming/prepare-libraries-for-trimming
    -->
    <IsTrimmable>true</IsTrimmable>

This way, new class libraries will be "trimmable" by default and be
able to react to trimming warnings.

We can also use `TrimMode=full` in many of our existing tests:

* MSBuild tests that assert 0 warnings can use `TrimMode=full`.

* On-device tests can import `trim-analyzers.props` and use `TrimMode=full`.

src/Microsoft.Android.Templates/android-bindinglib/AndroidBinding1.csproj

@@ -5,6 +5,11 @@
     <RootNamespace Condition="'$(name)' != '$(name{-VALUE-FORMS-}safe_namespace)'">AndroidBinding1</RootNamespace>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
+    <!--
+      Enable trim analyzers for Android class libraries.
+      To learn more, see: https://learn.microsoft.com/dotnet/core/deploying/trimming/prepare-libraries-for-trimming
+    -->
+    <IsTrimmable>true</IsTrimmable>
     <!--
       NOTE: you can simply add .aar or .jar files in this directory to be included in the project.
       To learn more, see: https://learn.microsoft.com/dotnet/maui/migration/android-binding-projects

src/Microsoft.Android.Templates/android-wear/AndroidApp1.csproj

@@ -11,6 +11,13 @@
     <ApplicationDisplayVersion>1.0</ApplicationDisplayVersion>
     <MSBuildWarningsAsMessages>$(MSBuildWarningsAsMessages);XA4218</MSBuildWarningsAsMessages>
   </PropertyGroup>
+  <!--
+    Enable full trimming in Release mode.
+    To learn more, see: https://learn.microsoft.com/dotnet/core/deploying/trimming/trimming-options#trimming-granularity
+  -->
+  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
+    <TrimMode>full</TrimMode>
+  </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Xamarin.AndroidX.Wear" Version="1.2.0.5" />
   </ItemGroup>

src/Microsoft.Android.Templates/android/AndroidApp1.csproj

@@ -10,4 +10,11 @@
     <ApplicationVersion>1</ApplicationVersion>
     <ApplicationDisplayVersion>1.0</ApplicationDisplayVersion>
   </PropertyGroup>
+  <!--
+    Enable full trimming in Release mode.
+    To learn more, see: https://learn.microsoft.com/dotnet/core/deploying/trimming/trimming-options#trimming-granularity
+  -->
+  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
+    <TrimMode>full</TrimMode>
+  </PropertyGroup>
 </Project>

src/Microsoft.Android.Templates/androidlib/AndroidLib1.csproj

@@ -5,5 +5,10 @@
     <RootNamespace Condition="'$(name)' != '$(name{-VALUE-FORMS-}safe_namespace)'">AndroidLib1</RootNamespace>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
+    <!--
+      Enable trim analyzers for Android class libraries.
+      To learn more, see: https://learn.microsoft.com/dotnet/core/deploying/trimming/prepare-libraries-for-trimming
+    -->
+    <IsTrimmable>true</IsTrimmable>
   </PropertyGroup>
 </Project>

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.DefaultProperties.targets

@@ -74,8 +74,9 @@
     <AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' and '$(PublishTrimmed)' == 'true' ">SdkOnly</AndroidLinkMode>
     <AndroidLinkMode Condition=" '$(AndroidLinkMode)' == '' ">None</AndroidLinkMode>
     <!-- For compat with user code not marked trimmable, only trim opt-in by default. -->
-    <TrimMode Condition=" '$(TrimMode)' == '' and '$(AndroidLinkMode)' == 'Full' ">link</TrimMode>
+    <TrimMode Condition=" '$(TrimMode)' == '' and '$(AndroidLinkMode)' == 'Full' ">full</TrimMode>
 		<TrimMode Condition="'$(TrimMode)' == ''">partial</TrimMode>
+    <SuppressTrimAnalysisWarnings Condition=" '$(SuppressTrimAnalysisWarnings)' == '' and '$(TrimMode)' == 'full' ">false</SuppressTrimAnalysisWarnings>
     <SuppressTrimAnalysisWarnings Condition=" '$(SuppressTrimAnalysisWarnings)' == '' ">true</SuppressTrimAnalysisWarnings>
     <!-- Prefer $(RuntimeIdentifiers) plural -->
     <RuntimeIdentifiers Condition=" '$(RuntimeIdentifier)' == '' And '$(RuntimeIdentifiers)' == '' ">android-arm;android-arm64;android-x86;android-x64</RuntimeIdentifiers>

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs

@@ -232,6 +232,10 @@ public void BuildHasNoWarnings (bool isRelease, bool xamarinForms, bool multidex
 				new XamarinFormsAndroidApplicationProject () :
 				new XamarinAndroidApplicationProject ();
 			proj.IsRelease = isRelease;
+			// Enable full trimming
+			if (!xamarinForms && isRelease) {
+				proj.TrimModeRelease = TrimMode.Full;
+			}
 			if (multidex) {
 				proj.SetProperty ("AndroidEnableMultiDex", "True");
 			}

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Android/AndroidLinkMode.cs

@@ -9,4 +9,10 @@ public enum AndroidLinkMode
 		SdkOnly,
 		Full,
 	}
+
+	public enum TrimMode
+	{
+		Partial,
+		Full,
+	}
 }

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Android/KnownProperties.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 
 namespace Xamarin.ProjectTools
 {
@@ -18,6 +18,7 @@ public static class KnownProperties
 		public const string RuntimeIdentifiers = "RuntimeIdentifiers";
 		public const string RunAOTCompilation = "RunAOTCompilation";
 		public const string PublishTrimmed = "PublishTrimmed";
+		public const string TrimMode = "TrimMode";
 		public const string SupportedOSPlatformVersion = "SupportedOSPlatformVersion";
 
 		public const string Deterministic = "Deterministic";

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Android/XamarinAndroidApplicationProject.cs

@@ -155,6 +155,11 @@ public AndroidLinkMode AndroidLinkModeRelease {
 			set { SetProperty (ReleaseProperties, KnownProperties.AndroidLinkMode, value.ToString ()); }
 		}
 
+		public TrimMode TrimModeRelease {
+			get => Enum.TryParse (GetProperty (ReleaseProperties, KnownProperties.TrimMode), out TrimMode trimMode) ? trimMode : TrimMode.Partial;
+			set => SetProperty (ReleaseProperties, KnownProperties.TrimMode, value.ToString ().ToLowerInvariant ());
+		}
+
 		public bool EnableMarshalMethods {
 			get { return string.Equals (GetProperty (KnownProperties.AndroidEnableMarshalMethods), "True", StringComparison.OrdinalIgnoreCase); }
 			set { SetProperty (KnownProperties.AndroidEnableMarshalMethods, value.ToString ()); }

tests/CodeGen-Binding/Xamarin.Android.JcwGen-Tests/Xamarin.Android.JcwGen-Tests.csproj

@@ -13,11 +13,16 @@
   </PropertyGroup>
 
   <Import Project="..\..\..\Configuration.props" />
+  <Import Project="$(XamarinAndroidSourcePath)\build-tools\trim-analyzers\trim-analyzers.props" />
 
   <PropertyGroup>
     <OutputPath>..\..\..\bin\Test$(Configuration)</OutputPath>
   </PropertyGroup>
 
+  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
+    <TrimMode Condition=" '$(TrimMode)' == '' ">full</TrimMode>
+  </PropertyGroup>
+
   <ItemGroup>
     <AndroidJavaSource Include="../Xamarin.Android.McwGen-Tests/java/**/*.java" />
     <Compile Remove="TimingTests.cs" />

tests/Mono.Android-Tests/Runtime-Microsoft.Android.Sdk/Mono.Android.NET-Tests.csproj

@@ -2,6 +2,7 @@
 
   <Import Project="..\..\..\Configuration.props" />
   <Import Project="..\Mono.Android-Test.Shared.projitems" Label="Shared" Condition="Exists('..\Mono.Android-Test.Shared.projitems')" />
+  <Import Project="$(XamarinAndroidSourcePath)\build-tools\trim-analyzers\trim-analyzers.props" />
 
   <PropertyGroup>
     <TargetFramework>$(DotNetAndroidTargetFramework)</TargetFramework>
@@ -19,7 +20,6 @@
     <EnableDefaultAndroidAssetItems>false</EnableDefaultAndroidAssetItems>
     <_MonoAndroidTestPackage>Mono.Android.NET_Tests</_MonoAndroidTestPackage>
     <PlotDataLabelSuffix>-$(TestsFlavor)NET6</PlotDataLabelSuffix>
-    <WarningsAsErrors>IL2037</WarningsAsErrors>
     <AndroidUseNegotiateAuthentication>true</AndroidUseNegotiateAuthentication>
     <AndroidNdkDirectory></AndroidNdkDirectory>
     <!--
@@ -36,6 +36,7 @@
 
   <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
     <AndroidLinkTool Condition=" '$(AndroidLinkTool)' == '' ">r8</AndroidLinkTool>
+    <TrimMode Condition=" '$(TrimMode)' == '' ">full</TrimMode>
   </PropertyGroup>
 
   <ItemGroup>