Move C++ projects to use PackageReference

[asklar]

Apparently PackageReference will work in C++ projects now. We should try it and see if there are any gaps, and if acceptable then remove the packages.config stuff as it complicates things.

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@asklar As it turns out, PackageReference support in C++ projects works today. You will need to do the following:

1. Add <ProjectCapability Include="PackageReferences" /> to an item group in your vcxproj file or a targets file included by it.
2. Add a Directory.Build.props file or above the project’s directory, and add an Import element to it with the following value: $(MSBuildProjectExtensionsPath)$(MSBuildProjectFile).*.props. (You can technically add this anywhere that MSBuild will see it, but I find that putting it in Directory.Build.props ensures that it is both included at the correct place, and is also easily shared between all the projects in your solution.)
3. Add a Directory.Build.targets file in the same location, and add an Import element to it with this value: $(MSBuildProjectExtensionsPath)$(MSBuildProjectFile).*.targets.
4. Unload and reload your C++ project(s).

After that, not only will NuGet packages auto-restore like with csproj, but the NuGet Package Manager UI will also add and remove PackageReference elements from the project instead of creating a packages.config file. (If this doesn’t seem to work, you may need to use the VS 16.11 beta; that’s what I’m using, and it works great for me.) Note that vcxproj will require you to run File > Save All before changes made in the NuGet UI will persist to the project file, as with any other changes to a vcxproj made using the GUI. Hope this helps!

Originally posted by @wjk in dotnet/project-system#2491 (comment)

References

• https://developercommunity.visualstudio.com/t/use-packagereference-in-vcxproj/351636
• https://github.com/jlaanstra/CppWinRT-PackageReference

[JunielKatarn]

I think @dannyvv tried this before, only native projects still rely on traditional NuGet locations (meaning, packages will still be stored in the packages relative folder).

This is definitely useful, however, as it reduces the possibility of version mismatches.

[wjk]

@JunielKatarn Not necessarily. I have used vcxproj PackageReference with both the global (per-user) NuGet package cache, and a local package cache set via the nuget.config file, and have never ran into any such problems. Keep in mind that either way, the packages will all be unpacked as siblings of the same directory (either the per-user cache, or the path set in the nuget.config file), just as with packages.config. IMHO, if a NuGet package requires a specific restore layout to function properly, that is a bug in that package that should be corrected. (All paths in props/targets files in NuGet packages should be relative to $(MSBuildThisFileDirectory).) What packages do you expect will give problems?

[JunielKatarn]

@wjk none specifically. Maybe I was misinformed?
If a Native C++ project can load the packages from the NuGet package cache instead of requiring an explicit location (usually relative to the VCXPROJ file), that would be a huge gain for us, because we wouldn't need to copy the packages for each local git clone.

Did I understand this correctly?

[wjk]

That’s correct! 🚀

[JunielKatarn]

That’s correct! 🚀

🤯
I guess I'll be submitting this enhancement for this project... TODAY, then.

One last question. Does this PackageReference mechanism work with plain NuGet.exe, or does it require some VS magic?

[wjk]

As it turns out, PackageReferences uses neither! Just run MSBuild.exe /t:Restore to download all needed packages, just as you would do with csproj (or run MSBuild.exe /restore to do so and then build the project).

[JunielKatarn]

Pretty much, pure modern MSBuild APIs, then.
Awesome.

[asklar]

Yeah I'm excited about the opportunity for simplification this brings!
If it requires a specific min version of VS, then that'd be important to know.

Today our C++ projects (both the framework as well as 3rd party libraries) have hardcoded dependencies to find nuget packages under the solution folder, so being able to remove all that would be great.

[wjk]

@asklar Support for C++ PackageReference in the VS GUI requires at least 16.9 per dotnet/project-system#6629, which was the last PR needed to implement this feature. Support for restoring C++ PackageReferences via the command line goes back much, much further.