[Spec] Transitive Warning Properties

This spec deals with the need for respecting the NoWarn properties from project references and the solution.

Current Status

As per the work done in restore warnings and errors users now experience NuGet warnings and errors as first class warnings and errors. Further, the work done in and warning properties support we allow users to add the following 3 msbuild properties to control this experience -

• TreatWarningsAsErrors - This accepts true/false and can be used to treat all warnings as errors including NuGet/Msbuild/CSC.

  <TreatWarningsAsErrors>True</TreatWarningsAsErrors>

• WarningsAsErrors - This accepts a comma or semi-colon separated list of NuGet warning codes and can be used to convert specific warnings to errors.

  <WarningsAsErrors>$(WarningsAsErrors);NU1603;NU1701</WarningsAsErrors>

• NoWarn - This accepts a comma or semi-colon separated list of NuGet warning codes and can be used to hide specific warnings.

  <NoWarn>$(NoWarn);NU1603;NU1605</NoWarn>

• Package Specific NoWarn - This accepts a comma or semi-colon separated list of NuGet warning codes and can be used to hide specific warnings for a specific package reference. This property has to be set on a package reference.

  <PackageReference Include="NuGet.Versioning" Version="4.1.5" NoWarn="NU1603" />
  or
  

  <PackageReference Include="NuGet.Versioning" Version="4.1.5">
    <NoWarn>NU1603</NoWarn>
  </PackageReference>
  

Combined Example -

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp1.1;net46</TargetFramework>
    <NoWarn>$(NoWarn);NU1603;NU1605</NoWarn>
    <WarningsAsErrors>NU1603;NU1701</WarningsAsErrors>
    <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="NuGet.Versioning" Version="4.1.5" NoWarn="NU1603" />
  </ItemGroup>
</Project>

Problem

Based on the work done above, we allow customers to control the warnings generated in one project. But currently we do not allow customers to control this experience for warnings being generated in a referenced project.

For example - ProjA -> ProjB -> PkgX[NU1603] In the above scenario, we have Project A that references Project B which references Package X. Further, consider that Package X is a cause of a NuGet restore warning NU1603.

Based on the current status above we allow the users to turn off restore warnings in Project B either for all NU1603 warnings by using the project wide NoWarn property. Or just for package X by using package specific NoWarn property.

But we do not allow users to control the same warnings in Project A. Thus when the user restores Project A, they need to turn off NU1603 by using a project wide setting, which can hide other NU1603 warnings generated in the project, Or add a direct reference to PackageX and then add a package specific NoWarn, which can alter the project's restore graph closure.

Solution

The solution is to transitively pull in NoWarn properties from all the project references. The effect should be that if a child project has no-warn'd a warning then the parent project should not see the warning while restoring.

To achieve this we need to traverse the parent project's restore closure to pull in all the child project NoWarn and then apply them to the warnings as they are generated.

Implementation Details

The current implementation is at https://github.com/NuGet/NuGet.Client/tree/dev-anmishr-p2pnowarn.

When a warning is generated in restore, it is passed to RestoreCollectorLogger. The logger then checks if it has the needed information to collect the transitive NoWarn properties