.NET Core 2.1 : How to trigger Copy task defined in the project file during debugging in the Visual Studio 2017? - msbuild

Question

There are some files residing in other directories that, I would like to copy to project folder automatically before build and publishing.
After some research and experimentation, I have come up with the following .csproj file.
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
<TargetFramework>netcoreapp2.1</TargetFramework>
<RuntimeFrameworkVersion>2.1.4</RuntimeFrameworkVersion>
<TieredCompilation>true</TieredCompilation>
<PreserveCompilationContext>true</PreserveCompilationContext>
</PropertyGroup>
<ItemGroup>
<APIDefinition Include="D:\SomePlace\*.API.*.yaml" />
</ItemGroup>
<Target Name="CopyFiles" BeforeTargets="Compile;Build;Publish">
<Copy SourceFiles="#(APIDefinition)" DestinationFolder="wwwroot" />
<Copy SourceFiles="D:\SomePlaceElse\BaseAPISettings.json" DestinationFolder="$(MSBuildProjectDirectory)" />
</Target>
<ItemGroup>
<Compile Remove="wwwroot\**\*;node_modules;bower_components" />
<None Update="**.user;**.vspscc">
<CopyToPublishDirectory>Never</CopyToPublishDirectory>
</None>
</ItemGroup>
<ItemGroup>
<PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.4" />
</ItemGroup>
</Project>
Here I have defined CopyFiles target, which should be run before the targets I've placed there. This target uses Copy task to copy YAML format API definition files and base API settings to the project directory.
This works well during build, publish etc. Also, if I delete the local file in the IDE, it instantly recopies it from the source.
Sometimes I make changes to these files between debugging sessions. Then, when I start debugging from Visual Studio, since the project files aren't changed, obviously the already built project is run.
Since the project is not built, my copy tasks are not triggered, and I end up with stale files during debuging.
Is there anything I can do to have my Copy tasks triggered, when I do "Start Debugging F5" in the IDE, regardless of the project build state ?
P.S. : I'm using Visual Studio 2017 15.8.5 and targeting .NET Core 2.1.4 runtime, if it makes any difference.

Answer 1

To integrate fully into the up-to-date check of the project system inside Visual Studio, I susggest the following changes:
Make the items' source and target paths known before
Register them to the up-to-date check system. (Also needs a hack to make sure the project source code is recompiled so that the output will have a newer time stamp)
Make the MSBuild target itself incremental. This also helps for command-line builds when the files don't have to be copied.
The complete changes look like this:
<ItemGroup>
<CustomCopyFile Include="..\TestFiles\*.API.*.yaml"
TargetPath="wwwroot\%(Filename)%(Extension)" />
<CustomCopyFile Include="..\TestFiles\BaseAPISettings.json"
TargetPath="%(Filename)%(Extension)" />
<UpToDateCheckInput Include="#(CustomCopyFile)" />
<UpToDateCheckBuild Include="#(CustomCopyFile->'%(TargetPath)')"
Original="#(CustomCopyFile)" />
<CustomAdditionalCompileInputs Include="#(CustomCopyFile->'%(TargetPath)')" />
</ItemGroup>
<Target Name="CopyFiles"
BeforeTargets="BeforeBuild;BeforePublish"
Inputs="#(CustomCopyFile)"
Outputs="#(CustomCopyFile->'%(TargetPath)')">
<Copy SourceFiles="#(CustomCopyFile)"
DestinationFiles="#(CustomCopyFile->'%(TargetPath)')" />
</Target>
CustomCopyFile now collects all the source files and we put the expected destination file name into the TargetPath metadata.
UpToDateCheckInput items tell Visual Studio to rebuild the project if one of these items change.
UpToDateCheckBuild items instruct Visual Studio to only check these items against special source items. This is redundant for this example project but may be helpful if the target path wasn't inside the project directory but some intermediate output (obj..) folder and no re-evaluation would see these new files. It would also be helpful if the files were also modified as part of processing (e.g. replacing variables inside the files).
CustomAdditionalCompileInputs is a hack here since the items are copied to the project folder and are considered to be "inputs to the output" automatically.. So we force the project to recompile if our source files change. If we don't do so, it would never consider the project up-to-date after a change to the source yaml files since they would be newer than the compiled app.dll file.