From 4b1ec579327190c18f519b6cd236b058040a0be5 Mon Sep 17 00:00:00 2001
From: Dean Ellis <dellis1972@googlemail.com>
Date: Wed, 26 Jun 2024 19:19:43 +0100
Subject: [PATCH] [Xamarin.Android.Build.Tasks] Support VS "Build Acceleration"
 (#9042)

Fixes: https://github.com/dotnet/android/issues/8581
Fixes: https://dev.azure.com/devdiv/DevDiv/_workitems/edit/2051915

Context: https://github.com/dotnet/project-system/blob/9c9efad1d986e38232cbd74bec9dbd794883a91c/docs/build-acceleration.md
Context: https://github.com/dotnet/project-system/blob/dd9431b535a6158060d7ab64597276eb2c354aab/docs/design-time-builds.md#targets-that-run-during-design-time-builds
Context: https://github.com/dotnet/project-system/blob/dd9431b535a6158060d7ab64597276eb2c354aab/docs/up-to-date-check.md#default-inputs-and-outputs
Context: https://github.com/dotnet/project-system/blob/dd9431b535a6158060d7ab64597276eb2c354aab/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/DesignTimeTargets/Microsoft.Managed.DesignTime.targets#L448-L449
Context: dc3ccf28cdbe9f8c0a705400b83c11a85c81a980

The Visual Studio Fast Up-to-Date Check (FUTDC) flags
`_Microsoft.Android.Resource.Designer.dll` (dc3ccf28) as newer than
the output assembly (which it is).  But this flagging also causes it
to incorrectly think the build is out of date.

	WARNING: Potential build performance issue in 'Foo.csproj'.
	The project does not appear up-to-date after a successful build:
	Input ResolvedCompilationReference item 'obj\Debug\net8.0-android\_Microsoft.Android.Resource.Designer.dll' (2023-12-11 11:34:12.546) has been modified since the last successful build started.

Fix this by removing `_Microsoft.Android.Resource.Designer.dll` from
the list of files checked.  To do so, we *must* remove the item from
the `@(ReferencePathWithRefAssemblies)` item group *before* the
[`CollectResolvedCompilationReferencesDesignTime`][0] target runs.
This is because that Target uses the [`Returns` attribute][1]; it
turns out you cannot modify the ItemGroup that is being returned
via the `Returns` attribute on a target.

Unfortunately there isn't a way to unit test this since the Fast Update
check *only* runs in Visual Studio.  The targets do not even exist on
the command line.

[0]: https://github.com/dotnet/project-system/blob/dd9431b535a6158060d7ab64597276eb2c354aab/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/DesignTimeTargets/Microsoft.Managed.DesignTime.targets#L448-L449
[1]: https://learn.microsoft.com/visualstudio/msbuild/target-element-msbuild?view=vs-2022
---
 .../Xamarin.Android.Resource.Designer.targets | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Resource.Designer.targets b/src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Resource.Designer.targets
index d0943e16bb9..389d1857e65 100644
--- a/src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Resource.Designer.targets
+++ b/src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Resource.Designer.targets
@@ -196,6 +196,28 @@ Copyright (C) 2016 Xamarin. All rights reserved.
   </ItemGroup>
 </Target>
 
+<!--
+  The Visual Studio FastUpdate check flags the Resource Designer assembly as
+  newer than the output assembly (which it is). But it causes it to incorrectly
+  think the build is out of date. 
+
+  So lets remove it. We MUST remove the item from the @ReferencePathWithRefAssemblies
+  ItemGroup BEFORE the CollectResolvedCompilationReferencesDesignTime target runs.
+  This is because that target uses the Returns functionality. It turns out you cannot
+  modify the ItemGroup that is being returned via a Returns on a target.
+-->
+<Target Name="_RemoveResourceDesignerFromResolvedComilationReferences"
+      BeforeTargets="CollectResolvedCompilationReferencesDesignTime"
+      Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'"
+>
+  <ItemGroup>
+    <_ResourceDesignerFiles Include="%(ReferencePathWithRefAssemblies.Identity)"
+        Condition="'%(ReferencePathWithRefAssemblies.OriginalPath)' == '$(_GenerateResourceDesignerAssemblyOutput)'"
+    />
+    <ReferencePathWithRefAssemblies Remove="@(_ResourceDesignerFiles)" />
+  </ItemGroup>
+</Target>
+
 <Target Name="_BuildResourceDesigner"
     Condition=" '$(AndroidUseDesignerAssembly)' == 'True' "
     DependsOnTargets="$(_BuildResourceDesignerDependsOn)" />