[One .NET] fix binding generation for .jar in application projects (#…

…6281)

Context: https://discord.com/channels/732297728826277939/732297837953679412/885897167900934175

Adding a single `.jar` file to a .NET 6 application project does not
produce bindings:

1. The file is added to `@(AndroidLibrary)` and
   `@(AndroidJavaLibrary)` item groups, but not `@(EmbeddedJar)` or
   `@(InputJar)`.
2. Any MSBuild targets related to C# binding generation are skipped.

I could reproduce this issue in a new test.

Note that `@(AndroidLibrary)` is the preferred item group going forward
in .NET 6. We still use the old names internally and support them in projects.
One day we could drop support for the old names?

To solve the issue, we can add `.jar` files to `@(InputJar)` for all
.NET 6 application projects in the `_CategorizeAndroidLibraries`
MSBuild target.

src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.AvailableItems.targets

@@ -87,6 +87,10 @@ This item group populates the Build Action drop-down in IDEs.
     <ItemGroup Condition=" '$(UsingAndroidNETSdk)' == 'true' ">
       <LibraryProjectZip  Include="@(AndroidLibrary)" Condition=" '%(AndroidLibrary.Extension)' == '.aar' and '%(AndroidLibrary.Bind)' == 'true' " />
     </ItemGroup>
+    <!-- .NET 6 application projects -->
+    <ItemGroup Condition=" '$(AndroidApplication)' == 'true' and '$(UsingAndroidNETSdk)' == 'true' ">
+      <InputJar Include="@(AndroidLibrary)" Condition=" '%(AndroidLibrary.Extension)' == '.jar' and '%(AndroidLibrary.Bind)' == 'true' " />
+    </ItemGroup>
     <!-- .NET 6 class libraries-->
     <ItemGroup Condition=" '$(AndroidApplication)' != 'true' and '$(UsingAndroidNETSdk)' == 'true' ">
       <AndroidAarLibrary  Include="@(AndroidLibrary)" Condition=" '%(AndroidLibrary.Extension)' == '.aar' and '%(AndroidLibrary.Bind)' != 'true' " />

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

@@ -288,6 +288,28 @@ public void DotNetLibraryAarChanges ()
 			}
 		}
 
+		[Test]
+		public void AppWithSingleJar ()
+		{
+			var proj = new XASdkProject {
+				Sources = {
+					new AndroidItem.AndroidLibrary ("Jars\\javaclasses.jar") {
+						BinaryContent = () => ResourceData.JavaSourceJarTestJar,
+					}
+				}
+			};
+
+			var dotnet = CreateDotNetBuilder (proj);
+			Assert.IsTrue (dotnet.Build (), "build should succeed");
+
+			var assemblyPath = Path.Combine (FullProjectDirectory, proj.OutputPath, $"{proj.ProjectName}.dll");
+			FileAssert.Exists (assemblyPath);
+			using (var assembly = AssemblyDefinition.ReadAssembly (assemblyPath)) {
+				var typeName = "Com.Xamarin.Android.Test.Msbuildtest.JavaSourceJarTest";
+				Assert.IsNotNull (assembly.MainModule.GetType (typeName), $"{assemblyPath} should contain {typeName}");
+			}
+		}
+
 		[Test]
 		public void GenerateResourceDesigner_false()
 		{