Resolve package references to projects

[natemcmaster]

In project.json, dependencies could be either a project or a package reference. NuGet and compilation would resolve the package vs project based on some conventions (like folder name) and the global.json file. Futhermore, VS would automatically add new projects to the solution explorer when the were discovered.

In MSBuild, there is no equivalent feature. References are either ProjectReference or PackageReference. Swapping a package reference to a project is not always straight forward. In cases where the package is a transitive reference from other PackageReferences, you have to keep the PackageReference and set ExcludeAssets=All in order to avoid conflicts between ProjectReference and PackageReference. (See https://docs.microsoft.com/en-us/nuget/schema/msbuild-targets#replacing-one-library-from-a-restore-graph). It also requires manually adding new projects to the sln file so they appear in VS.

It would be nice to provide a way to resolve PackageReference to projects without requiring changes to csproj.

---

Some data on this:

• The ASP.NET team frequently needs this as we debug components across multiple solutions. We've attempted to automate this with scripting. (See this script in Kestrel). cc @pakrym
• ASP.NET core benchmark automation also had to implement a way to resolve package references as projects. Implementing this required writing code that hunts for PackageReference and edits the csproj file locally. See Restore source dependencies feature (#185) aspnet/Benchmarks#190 cc @mikeharder
• I've been asked about this several times from non-Microsoft devs
  • http://www.natemcmaster.com/blog/2017/01/19/project-json-to-csproj/#comment-3203817959
  • http://www.natemcmaster.com/blog/2017/02/01/project-json-to-csproj-part2/#comment-3206867094
  • http://www.natemcmaster.com/blog/2017/03/09/vs2015-to-vs2017-upgrade/#comment-3273066914
  • Twitter: https://twitter.com/digory/status/846119886426271744
• StackOverflow question: http://stackoverflow.com/questions/42773815/net-core-csproj-global-json-projects-equivalent

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cc @davidfowl @dsplaisted

[dsplaisted]

This is possible to some degree today. If you have a ProjectReference, it will override any package references to the same package ID in the restore graph. You don't need the PrivateAssets=all PackageReference shown in the docs when want to replace the package with a project reference instead of a reference to a DLL.

Some caveats:

• For things to work in VS, you need to add the projects to your solution
• You may need to add feeds to your NuGet.config to match those that apply to the source code you're bringing in
• The package version for the project needs to be at least as high as any package dependencies on it require. So if the source code you're bringing in doesn't set the package version (ie if that's a parameter that's only passed in when you pack, for example), then you'll get downgrade warnings. This is a NuGet issue: Avoid downgrade warnings for Package vs Project checks NuGet/Home#4620

@CesarBS got this working for the ASP.NET benchmarks repo: aspnet/Benchmarks#190

[davidfowl]

@dsplaisted It's such a bad experience though. We need something comparable to what project.json had. It needs to be obvious and it needs to just work without the caveats listed. On top of that, it doesn't work well in VS if the projects aren't added to the solution (something xproj did automatically)

[cwe1ss]

Getting this feature back would be awesome!

With global.json, it was pretty easy to mistakenly commit the "wrong" global.json/sln file with the local debug paths. It would show up as a broken build on the CI server so it's not the end of the world. I'm just wondering if there's any chance of doing this without touching any of the committed files? Maybe the overrides could be stored in the .suo file or in a separate MySolution.sln.overrides file which could be added to the .gitignore file.

[danielmurrmann]

@davidfowl I completly agree to you. The developer experience on dnx with project.json was great. especially in the case of debugging into a nuget package from own code. You had just to clone the git repository and set one path in global json. Had to make not a single Change to my project. I couldn't be easier. I can't understand why Microsoft has thrown away such a great feature when all this was already a release candidate and very close to a final release.

[mclark1129]

I also created a uservoice to restore this or similar tooling within VS.

https://visualstudio.uservoice.com/forums/121579-visual-studio-ide/suggestions/19071868-restore-global-json-functionality-in-vs2017

[tmitchel2]

I've been crying out for this for years, https://lernajs.io/ does something very similar (functionality, not implementation obviously) in the node.js world and it works really well.

[khirakawa]

For anyone who is looking to try the conditional reference solution accepted in this SO question to workaround this issue, note that conditional references aren't currently supported when doing nuget restores NuGet/Home#4996. Restoring nuget packages from VS GUI seems to work fine though.

[ToddThomson]

Here is a manual process that works for me:

1. When using debug configuration and source exists: Use project reference(s)

2. Otherwise utilize the package reference(s)
   Packages are created by CI with a custom msbuild target to generate the PackageVersion ( semver version 2 ) number when commits are pushed to the TFS Server.

3. When changing the project build configuration ( Debug <-> Release ) the project must be unloaded/reloaded ( there might be a better way, but I rarely need to move from the Debug configuration ).

4. TFS CI produces the Release build configuration packages with PackageVersion using:
   version.props imported from Directory.Build.props

Project>
  <PropertyGroup>
    <VersionPrefix>0.9.0</VersionPrefix>
    <VersionSuffix>ci</VersionSuffix>
  </PropertyGroup>
</Project>

file: Directory.Build.targets

<Project>
  
  <Target Name="SetVersion" BeforeTargets="Build" >
    <PropertyGroup>
      <BuildNumber>$([System.DateTime]::Now.ToString(yyyyMMdd-mmss))</BuildNumber>
      <PackageVersion Condition="'$(VersionSuffix)' != '' AND '$(BuildNumber)' != ''">$(VersionPrefix)-$(VersionSuffix)-$(BuildNumber)</PackageVersion>      
    </PropertyGroup>
  </Target>
  
</Project>

project csproj snippet

  <Choose>
    <When Condition="'$(Configuration)' == 'Debug' AND Exists('..\..\..\Acme')">
      <ItemGroup Condition="'$(Configuration)' == 'Debug'">
        <ProjectReference Include="..\..\Acme.Composition\Acme.Composition\Acme.Composition.csproj" />
      </ItemGroup>
    </When>
    <Otherwise>
      <ItemGroup>
        <PackageReference Include="Acme.Composition" Version="0.9.0-ci-*" />
      </ItemGroup>
    </Otherwise>
  </Choose>