behaviour of sdk 5.0.2 and higher with .editorconfig differs from previous sdks

[askazakov]

Version Used:

dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.302
 Commit:    c005824e35

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  11.0
 OS Platform: Darwin
 RID:         osx.11.0-x64
 Base Path:   /usr/local/share/dotnet/sdk/5.0.302/

Host (useful for support):
  Version: 5.0.8
  Commit:  35964c9215

.NET SDKs installed:
  3.1.102 [/usr/local/share/dotnet/sdk]
  3.1.409 [/usr/local/share/dotnet/sdk]
  5.0.104 [/usr/local/share/dotnet/sdk]
  5.0.205 [/usr/local/share/dotnet/sdk]
  5.0.302 [/usr/local/share/dotnet/sdk]

Steps to Reproduce:

1. dotnet new console
2. Add <TreatWarningsAsErrors>True</TreatWarningsAsErrors> to .csproj
3. Add Directory.Build.props with

<Project>
    <ItemGroup>
        <PackageReference Include="SonarAnalyzer.CSharp" Version="8.26.0.34506">
            <PrivateAssets>all</PrivateAssets>
            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
        </PackageReference>
    </ItemGroup>
</Project>

4. Add .editorconfig with

[*.cs]
# Remove unnecessary 'using' https://rules.sonarsource.com/csharp/RSPEC-1128
dotnet_diagnostic.S1128.severity = warning

5. Replace Program.cs with

using System;

namespace example
{
    internal static class Program
    {
        private static void Main(string[] args)
        {
            // Method intentionally left empty.
        }
    }
}

6a. Add global.json with

  "sdk": {
    "version": "5.0.104"
  }
}

or
6b. Add global.json with

  "sdk": {
    "version": "5.0.205"
  }
}

7. dotnet build

Expected Behavior:
Build output will the same
Actual Behavior:
for sdk 5.0.104 I've got

Program.cs(1,1): warning S1128: Remove this unnecessary 'using'. [...]
    1 Warning(s)
    0 Error(s)

for sdk 5.0.205 I've got

Program.cs(1,1): error S1128: Remove this unnecessary 'using'. [...]
    0 Warning(s)
    1 Error(s)

Sdk 5.0.3xx acts like 5.0.2xx

Which one is correct? Is it introduced or fixed bug between 5.0.1 and 5.0.2?

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[Youssef1313]

This should have been fixed in #48125. Not sure if 5.0.2 has the fix or not. cc @mavasani

[jmarolf]

as @Youssef1313 says 5.0.3xx behavior is correct. placing <TreatWarningsAsErrors>True</TreatWarningsAsErrors> in your project overrides all other options meaning all warnings are errors.