From 58e451b6661713b0338f276e508c12450b3e8a3b Mon Sep 17 00:00:00 2001
From: Jonathan Peppers <jonathan.peppers@microsoft.com>
Date: Fri, 31 Aug 2018 13:43:45 -0500
Subject: [PATCH] [Xamarin.Android.Build.Tasks] simplify inputs to
 _CompileToDalvik

Recently I've been discovering more and more places where usage of
`**\*.*` can hurt the performance of our build.

In this case, the `_FindCompiledJavaFiles` target:

    <Target Name="_FindCompiledJavaFiles" DependsOnTargets="_CompileJava">
        <CreateItem Include="$(IntermediateOutputPath)android\bin\classes\\**\*.class">
            <Output TaskParameter="Include" ItemName="_CompiledJavaFiles" />
        </CreateItem>
    </Target>

This target is running even in builds with no changes, so we are
*always* recursing directories and finding `*.class` files.

But since we are using a `classes.zip` file now, we don't need to
recurse and find the `*.class` files at all anymore!

I was able to remove this target completely, and change
`$(_CompileToDalvikInputs)` to use
`$(IntermediateOutputPath)android\bin\classes.zip`. Less inputs also
help build times, because MSBuild won't have to evaluate timestamps on
all the `*.class` files. It can just look at the single `classes.zip`
file.

To see the difference, a build with no changes was taking:

    46 ms  _FindCompiledJavaFiles                     1 calls
    15 ms  _CompileToDalvikWithDx                     1 calls

After these changes:

    4 ms  _CompileToDalvikWithDx                     1 calls

`_FindCompiledJavaFiles` is gone completely.

I also made sure to include `_CompileJava` in
`$(_CompileToDalvikDependsOnTargets)` in place of
`_FindCompiledJavaFiles`.
---
 .../Xamarin.Android.Common.targets                    | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
index 6d018c2b0d1..38997de0a12 100755
--- a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
+++ b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
@@ -2470,16 +2470,9 @@ because xbuild doesn't support framework reference assemblies.
   </CreateItem>
 </Target>
 
-<Target Name="_FindCompiledJavaFiles" DependsOnTargets="_CompileJava">
-  <CreateItem
-    Include="$(IntermediateOutputPath)android\bin\classes\\**\*.class">
-    <Output TaskParameter="Include" ItemName="_CompiledJavaFiles" />
-  </CreateItem>
-</Target>
-
 <PropertyGroup>
 	<_CompileToDalvikDependsOnTargets>
-		_FindCompiledJavaFiles;
+		_CompileJava;
 		_GetMonoPlatformJarPath;
 		_GetAdditionalResourcesFromAssemblies;
 		_CreateAdditionalResourceCache;
@@ -2489,7 +2482,7 @@ because xbuild doesn't support framework reference assemblies.
 		$(MSBuildAllProjects)
 		;@(_JavaLibrariesToCompileForAppDx)
 		;@(AndroidExternalJavaLibrary)
-		;@(_CompiledJavaFiles)
+		;$(IntermediateOutputPath)android\bin\classes.zip
 		;@(ProguardConfiguration)
 		;@(MultiDexMainDexList)
 		;$(_AndroidBuildPropertiesCache)