How to pack a referenced project into a nuget package?

I have a C# solution which contains 3 projects; Application.Server, Application.Client, and Application.Common. Both server and client have a project reference to common.

I want to pack server and client up so that they can be used by other teams in my organisation. I have some automated build pipeline set up that do so, and they publish the nuget packages for server and client. They do not package or publish common. When I inspect the nuget packages, I can see that they reference the common package.

Is there a way that I can get them to build that project into them self? Ideally I don't want to publish the common package as it's pretty specific to my application, and it doesn't really make sense that it's something that's independently consumable by other departments. I also don't want to have to worry about wrangling extra nuget packages if I can help it (as in reality, Common is actually several projects).

If your projects are "old style"/non-SDK/traditional csproj, AND if any project uses a NuGet package, if all those NuGet references are defined using packages.config, then use you can use nuget.exe pack -IncludeReferencedProjects. However, if any of your projects use PackageReference to define their package references (new, SDK-style projects can only use PackageReference), then nuget.exe pack will not correctly create NuGet dependencies for those packages. For SDK style multi-targeting projects, nuget pack will probably completely fail.

The only supported way to pack projects that use PackageReference, or any SDK style project, is to use NuGet's MSBuild pack target (either dotnet pack or msbuild -t:pack). However, this does not have an equivalent to nuget.exe's IncludeReferencedProjects.

If your projects are SDK style, it really shouldn't be any more difficult to create and publish one package or many packages. Simply run dotnet pack on your solution, and every packable project gets packed (remember to mark any class library project you don't want to become a package as not packable). Then use your favourite scripting language to find and publish all nupkg files. For example (Get-ChildItem -Recurse -Filter *.nupkg $SLN_DIR | ForEach-Object { & dotnet nuget push $_ }, or copy/move all nupkgs to a single place (or use the appropriate setting to make NuGet create the packages there in the first place) and use dotnet nuget push *.nupkg.

The NuGet team recommends one package per assembly, and the tooling automatically creates NuGet dependencies for project references, so it all "just works" out of the box. To create a package with all the assemblies included, instead of NuGet dependencies, requires you to do a bunch of work.

Put the following into ./Directory.Build.targets

<Project>
  <PropertyGroup>
    <TargetsForTfmSpecificBuildOutput>$(TargetsForTfmSpecificBuildOutput);IncludeP2POutput</TargetsForTfmSpecificBuildOutput>
  </PropertyGroup>

  <Target Name="IncludeP2POutput" DependsOnTargets="ResolveReferences">
    <ItemGroup>
      <BuildOutputInPackage Include="@(ReferenceCopyLocalPaths->WithMetadataValue('ReferenceSourceTarget', 'ProjectReference')->WithMetadataValue('PrivateAssets', 'all'))" />
    </ItemGroup>
  </Target>
</Project>

Then add PrivateAssets="all" to all ProjectReference's you want to be packed into parent's package.

Here's how the recommendation works step-by-step:

1. Create or update ./Directory.Build.targets file:
   In the root directory of your project or solution, create or update the Directory.Build.targets file. This file allows you to customize the build process across all projects in your solution.

2. Define a custom build target:
   Within the ./Directory.Build.targets file, define a custom build target named IncludeP2POutput. This target will be executed during the build process and will determine which project references to include in the parent project's NuGet package.

3. Modify the TargetsForTfmSpecificBuildOutput property:
   The TargetsForTfmSpecificBuildOutput property is used by the .NET build system to determine which targets should be executed during the build process for a specific target framework. By adding IncludeP2POutput to this property, you're telling the build system to run the custom build target for each target framework of the parent project.

4. Add PrivateAssets="all" to relevant ProjectReference elements:
   In your parent project (the one that references other projects), locate the ProjectReference elements that you want to include in the NuGet package. Add the attribute PrivateAssets="all" to these ProjectReference elements. This attribute tells the build system to treat these references as private assets, meaning they won't be treated as dependencies by the consuming projects.

5. Custom build target logic:
   The custom build target IncludeP2POutput is triggered during the build process and runs after the ResolveReferences target (a built-in target). Inside the target, an ItemGroup is defined to select the project references with the specified metadata values (ReferenceSourceTarget set to 'ProjectReference' and PrivateAssets set to 'all'). These references are then added to the BuildOutputInPackage item group.

By following these steps, when you run dotnet pack on the parent project, the selected project references with PrivateAssets="all" will be included in the NuGet package of the parent project. Other projects consuming the parent project as a package will not see these references as dependencies, making them effectively hidden.

Please note that the behavior and capabilities of the .NET SDK and build system may evolve over time, so it's essential to refer to the official Microsoft documentation and release notes for the most up-to-date information on this topic.