Directory.Build.props

<Project>

  <PropertyGroup>
    <!-- The solution builds with zero warnings and no suppressions anywhere (no
         #pragma warning disable, no NoWarn). That was true by discipline only;
         this makes the build enforce it, so the next nullability or obsolete-API
         warning has to be dealt with rather than scrolled past. -->
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>

    <!-- Except the NuGet audit warnings. Those appear when an advisory is
         published against an already-referenced package, which would break
         unrelated pull requests through no change of theirs. They stay visible
         as warnings and are handled deliberately. -->
    <WarningsNotAsErrors>NU1901;NU1902;NU1903;NU1904</WarningsNotAsErrors>
  </PropertyGroup>

</Project>