[templates] remove Directory.Build.targets, add @(ProjectCapability)

[jonathanpeppers]

Description of Change

The Directory.Build.targets files in the templates were a collection
of workarounds that were needed until .NET MAUI was a workload. When
.NET MAUI was a NuGet package, this was the only way to set required
values for the IDE before NuGet restore. In the early days, you had to
unload/reload MAUI projects after NuGet restore.

We can remove Directory.Build.targets from templates now, and
consolidate @(ProjectCapability) so this is defined by the workload.

The following capabilities are defined for the IDE:

• Maui
• MauiSingleProject, LaunchProfiles, XamarinStaticLaunchProfiles
  when $(SingleProject) is true

These new capabilities are defined to identify projects (via telemetry)
that bring in portions of .NET MAUI:

• MauiAssets
• MauiBlazor
• MauiCore
• MauiEssentials

Other changes:

• $(_KeepLaunchProfiles) is set by default when $(SingleProject)
  is true.
• WinUI workarounds are moved into WinUI.SingleProject.targets.
• Fixed sdk-manifests casing for src/DotNet/DotNet.csproj -t:Install

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)
• Targets a single property for a single control (or intertwined few properties)
• Adds the property to the appropriate interface
• Avoids any changes not essential to the handler property
• Adds the mapping to the PropertyMapper in the handler
• Adds the mapping method to the Android, iOS, and Standard aspects of the handler
• Implements the actual property updates (usually in extension methods in the Platform section of Core)
• Tags ported renderer methods with [PortHandler]
• Adds an example of the property to the sample project (MainPage)
• Adds the property to the stub class
• Implements basic property tests in DeviceTests

Does this PR touch anything that might affect accessibility?

No

[jonathanpeppers]

/cc @joj @tondat this is probably the portion related to the IDE.

@tondat I tried to mark you as a reviewer, but maybe you don't have contributor access on this repo.

[jonathanpeppers]

@tondat is suggesting in Teams we might change to:

<ItemGroup>
  <ProjectCapability Include="MauiSingleProject" />
  <ProjectCapability Include="LaunchProfilesGroupByPlatformFilters"/>
  <ProjectCapability Include="BuildOnlyActiveTargetFrameworkOnDebug" />
</ItemGroup>

Also, a target that would improve the developer loop (until we get the appropriate Project System changes);

<Target Name="ComputeXamarinTargetFrameworks" BeforeTargets="_ComputeTargetFrameworkItems">
  <PropertyGroup>
    <TargetFrameworks Condition="'$(TargetFramework)' == '' AND '$(_SelectedTargetFramework)' != ''">$(_SelectedTargetFramework)</TargetFrameworks>
  </PropertyGroup>
  <Message Text="SelectedTargetFramework = $(_SelectedTargetFramework)" />
  <Message Text="TargetFramework = $(TargetFramework)" />
  <Message Text="TargetFrameworks = $(TargetFrameworks)" />
  <Message Text="BuildingInsideVisualStudio = $(BuildingInsideVisualStudio)" />
</Target>

I'll want to test this target a bit, and probably refactor it.

[jonathanpeppers]

Final capabilities might be:

<ItemGroup>
  <ProjectCapability Include="MauiSingleProject" />
  <ProjectCapability Include="XamarinStaticLaunchProfiles" Condition=" '$(VisualStudioVersion)' &lt; '17.0' " />
  <ProjectCapability Include="LaunchProfilesGroupByPlatformFilters" Condition=" '$(VisualStudioVersion)' &gt;= '17.0' " />
  <ProjectCapability Include="BuildOnlyActiveTargetFrameworkOnDebug" />
</ItemGroup>

LaunchProfilesGroupByPlatformFilters is Dev17-only, and you can't have XamarinStaticLaunchProfiles at the same time.

[jonathanpeppers]

ComputeXamarinTargetFrameworks target

It does not appear that adding this target will currently work:

<Target Name="ComputeXamarinTargetFrameworks" BeforeTargets="_ComputeTargetFrameworkItems">
  <PropertyGroup>
    <TargetFrameworks Condition="'$(TargetFramework)' == '' AND '$(_SelectedTargetFramework)' != ''">$(_SelectedTargetFramework)</TargetFrameworks>
  </PropertyGroup>
  <Message Text="SelectedTargetFramework = $(_SelectedTargetFramework)" />
  <Message Text="TargetFramework = $(TargetFramework)" />
  <Message Text="TargetFrameworks = $(TargetFrameworks)" />
  <Message Text="BuildingInsideVisualStudio = $(BuildingInsideVisualStudio)" />
</Target>

This needs to run in the "outer" build when $(TargetFramework) is blank and $(TargetFrameworks) plural is set. The "outer" build does not even load .NET workloads, those are loaded when $(TargetFramework) is set in the "inner" build. I currently do not see a way to provide this target from MAUI.

ProjectCapability

I think the current logic here is right, but my IDE isn't working as expected. I don't have a way to select my Android emulator, it fails to deploy when I hit the Play button:

TBD if this is an IDE issue, or something else related to workloads.

[jonathanpeppers]

$(TargetPlatformIdentifier) changed to Android, proper case, and that caused the IDE issue. See:

• dotnet/android@15f2310
• https://github.com/xamarin/XamarinVS/pull/12385

[Redth]

@mattleibow can we remove this now?

[mattleibow]

Maybe. I know I did in my pr and I think the issue was that we were using Xcode 12. Now with Xcode 13 all over, we probably can remove it.

[mattleibow]

Does this come in late enough? The WinUI targets from the nugets create this target, and we have to overwrite with a dummy.

[jonathanpeppers]

This is imported as late as a workload can do it:

maui/src/Workload/Microsoft.Maui.Controls.Sdk/Sdk/Microsoft.Maui.Controls.Sdk.After.targets

Line 9 in f95c2e5

<Import Project="WinUI.targets" Condition=" '$(TargetPlatformIdentifier)' == 'windows' " />

maui/src/Workload/Microsoft.Maui.Controls.Sdk/Sdk/Microsoft.Maui.Controls.Sdk.targets

Lines 14 to 16 in f95c2e5

	<PropertyGroup>
	<AfterMicrosoftNETSdkTargets>$(AfterMicrosoftNETSdkTargets);$(MSBuildThisFileDirectory)Microsoft.Maui.Controls.Sdk.After.targets</AfterMicrosoftNETSdkTargets>
	</PropertyGroup>

We'd need to test, but if it doesn't work we'd have to put the Directory.Build.targets back.

[mattleibow]

/azp run

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