From 9b060fab1bfe5c3229aa1eb10f47a16892a77e7c Mon Sep 17 00:00:00 2001
From: Jonathan Peppers <jonathan.peppers@microsoft.com>
Date: Fri, 22 Nov 2019 09:39:04 -0600
Subject: [PATCH] [Xamarin.Android.Build.Tasks] copy all assembles to
 android/assets/shrunk

In the case where `$(AndroidLinkMode)` is not `None`, we run a
`<RemoveRegisterAttribute/>` to remove all `[Register]` attributes
from `Mono.Android.dll`. This is a step to save on APK size.

However, we found that the AOT compiler is seeing *two*
`Mono.Android.dll` files:

* obj\Debug\android\assets\Mono.Android.dll
* obj\Debug\android\assets\shrunk\Mono.Android.dll

@vargaz pointed out that this is bad, some of the AOT images will be
linked against the wrong one and fail to load at runtime. We could
possibly be silently falling back to the JIT...

I first attempted to just remove the `shrunk` directory and write
`Mono.Android.dll` *in place*. This idea didn't pan out:

https://github.com/xamarin/xamarin-android/pull/3925#issuecomment-557566329

That idea broke incremental builds... So the next idea is to just copy
*every assembly* into the `android\assets\shrunk` directory. Then the
`AOT` compiler only operates against the `shrunk` directory.

This should only happen during `Release` builds, so the build
performance hit should be OK. We can also investigate removing
`[Register]` from *all* assemblies in a future PR, as that will likely
save further APK size from the support libraries, Google Play
Services, etc.
---
 .../Xamarin.Android.Common.targets            | 48 ++++++++++++++-----
 1 file changed, 35 insertions(+), 13 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
index d8d84ba676d..7ca2a8e2660 100644
--- a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
+++ b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
@@ -2041,6 +2041,30 @@ because xbuild doesn't support framework reference assemblies.
     <Output TaskParameter="Include" ItemName="_ResolvedFrameworkAssemblies" />
   </CreateItem>
 
+  <CreateItem
+    Include="@(_ResolvedAssemblies)"
+    Condition="'$(AndroidLinkMode)' == 'None' OR '$(AndroidUseSharedRuntime)' == 'true'">
+    <Output TaskParameter="Include" ItemName="_ShrunkAssemblies" />
+  </CreateItem>
+
+  <CreateItem
+    Include="@(_ResolvedAssemblies->'$(MonoAndroidIntermediateAssemblyDir)shrunk\%(Filename)%(Extension)')"
+    Condition="'$(AndroidLinkMode)' != 'None' AND '$(AndroidUseSharedRuntime)' != 'true'">
+    <Output TaskParameter="Include" ItemName="_ShrunkAssemblies" />
+  </CreateItem>
+
+  <CreateItem
+    Include="@(_ResolvedUserAssemblies)"
+    Condition="'$(AndroidLinkMode)' == 'None' OR '$(AndroidUseSharedRuntime)' == 'true'">
+    <Output TaskParameter="Include" ItemName="_ShrunkUserAssemblies" />
+  </CreateItem>
+
+  <CreateItem
+    Include="@(_ResolvedUserAssemblies->'$(MonoAndroidIntermediateAssemblyDir)shrunk\%(Filename)%(Extension)')"
+    Condition="'$(AndroidLinkMode)' != 'None' AND '$(AndroidUseSharedRuntime)' != 'true'">
+    <Output TaskParameter="Include" ItemName="_ShrunkUserAssemblies" />
+  </CreateItem>
+
   <CreateItem
     Include="@(_ResolvedFrameworkAssemblies)"
     Condition="'$(AndroidLinkMode)' == 'None' OR '$(AndroidUseSharedRuntime)' == 'true'">
@@ -2520,20 +2544,19 @@ because xbuild doesn't support framework reference assemblies.
   Condition="'$(AndroidLinkMode)' != 'None' AND '$(AndroidUseSharedRuntime)' != 'true'">
 
   <!-- Make a copy of every assembly into assets\shrunk -->
-  <Copy
-    SourceFiles="@(_ResolvedFrameworkAssemblies)"
-    DestinationFiles="@(_ShrunkFrameworkAssemblies)"
-    SkipUnchangedFiles="true" />
+  <CopyIfChanged
+    SourceFiles="@(_ResolvedAssemblies)"
+    DestinationFiles="@(_ShrunkAssemblies)" />
 
   <CopyIfChanged
-    SourceFiles="@(_ResolvedFrameworkAssemblies->'%(Identity).config')"
-    DestinationFiles="@(_ShrunkFrameworkAssemblies->'%(Identity).config')" />
+    SourceFiles="@(_ResolvedAssemblies->'%(Identity).config')"
+    DestinationFiles="@(_ShrunkAssemblies->'%(Identity).config')" />
   
   <!-- Shrink Mono.Android.dll by removing attribute only needed for GenerateJavaStubs -->
   <RemoveRegisterAttribute
     Condition="'$(AndroidLinkMode)' != 'None' AND '$(AndroidUseSharedRuntime)' != 'true'"
     Deterministic="$(Deterministic)"
-    ShrunkFrameworkAssemblies="@(_ShrunkFrameworkAssemblies)" />
+    ShrunkFrameworkAssemblies="@(_ShrunkAssemblies)" />
 
   <MakeDir Directories="$(MonoAndroidIntermediateAssemblyDir)shrunk" />
   <Touch Files="$(_RemoveRegisterFlag)" AlwaysCreate="true" />
@@ -2678,8 +2701,7 @@ because xbuild doesn't support framework reference assemblies.
 	<_BuildApkEmbedInputs>
 		$(MSBuildAllProjects)
 		;$(_PackagedResources)
-		;@(_ResolvedUserAssemblies)
-		;@(_ShrunkFrameworkAssemblies)
+		;@(_ShrunkAssemblies)
 		;@(AndroidNativeLibrary)
 		;@(_DexFile)
 		;$(_AndroidBuildPropertiesCache)
@@ -2717,7 +2739,7 @@ because xbuild doesn't support framework reference assemblies.
 	AndroidSequencePointsMode="$(_SequencePointsMode)"
 	AotAdditionalArguments="$(AndroidAotAdditionalArguments)"
 	ExtraAotOptions="$(AndroidExtraAotOptions)"
-	ResolvedAssemblies="@(_ResolvedUserAssemblies);@(_ShrunkFrameworkAssemblies)"
+	ResolvedAssemblies="@(_ShrunkAssemblies)"
 	AotOutputDirectory="$(_AndroidAotBinDirectory)"
 	IntermediateAssemblyDir="$(MonoAndroidIntermediateAssemblyDir)"
 	LinkMode="$(AndroidLinkMode)"
@@ -2742,7 +2764,7 @@ because xbuild doesn't support framework reference assemblies.
 		Condition="'$(BundleAssemblies)' == 'True'"
 		KeepTemp="$(AndroidMakeBundleKeepTemporaryFiles)"
 		AndroidNdkDirectory="$(_AndroidNdkDirectory)"
-		Assemblies="@(_ResolvedUserAssemblies);@(_AndroidResolvedSatellitePaths);@(_ShrunkFrameworkAssemblies)"
+		Assemblies="@(_ShrunkAssemblies);@(_AndroidResolvedSatellitePaths)"
 		IncludePath="$(MonoAndroidIncludeDirectory)"
 		SupportedAbis="@(_BuildTargetAbis)"
 		TempOutputPath="$(IntermediateOutputPath)"
@@ -2759,7 +2781,7 @@ because xbuild doesn't support framework reference assemblies.
     BundleAssemblies="$(BundleAssemblies)"
     BundleNativeLibraries="$(_BundleResultNativeLibraries)"
     EmbedAssemblies="$(EmbedAssembliesIntoApk)"
-    ResolvedUserAssemblies="@(_ResolvedUserAssemblies);@(_AndroidResolvedSatellitePaths)"
+    ResolvedUserAssemblies="@(_ShrunkUserAssemblies);@(_AndroidResolvedSatellitePaths)"
     ResolvedFrameworkAssemblies="@(_ShrunkFrameworkAssemblies)"
     NativeLibraries="@(AndroidNativeLibrary)"
     ApplicationSharedLibraries="@(_ApplicationSharedLibrary)"
@@ -2788,7 +2810,7 @@ because xbuild doesn't support framework reference assemblies.
       BundleAssemblies="$(BundleAssemblies)"
       BundleNativeLibraries="$(_BundleResultNativeLibraries)"
       EmbedAssemblies="$(EmbedAssembliesIntoApk)"
-      ResolvedUserAssemblies="@(_ResolvedUserAssemblies);@(_AndroidResolvedSatellitePaths)"
+      ResolvedUserAssemblies="@(_ShrunkUserAssemblies);@(_AndroidResolvedSatellitePaths)"
       ResolvedFrameworkAssemblies="@(_ShrunkFrameworkAssemblies)"
       NativeLibraries="@(AndroidNativeLibrary)"
       ApplicationSharedLibraries="@(_ApplicationSharedLibrary)"