WarningLevel is not set to match AnalysisLevel

[sliekens]

Type of issue

Other (describe below)

Description

In the WarningLevel section (link), there is a note about the use of AnalysisLevel which suggests that setting AnalysisLevel will also set WarningLevel to match.

However, I think this information is incorrect or misleading.

Example project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <AnalysisLevel>none</AnalysisLevel>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
  </PropertyGroup>

</Project>

Example Program.cs:

class program
{
    static void Main() { }
}

Output of dotnet build:

MSBuild version 17.9.8+b34f75857 for .NET
  Determining projects to restore...
  Restored /proof/proof.csproj (in 57 ms).
/proof/Program.cs(1,7): error CS8981: The type name 'program' only contains lower-cased ascii characters. Such names may become reserved for the language. [/proof/proof.csproj]

Build FAILED.

/proof/Program.cs(1,7): error CS8981: The type name 'program' only contains lower-cased ascii characters. Such names may become reserved for the language. [/proof/proof.csproj]
    0 Warning(s)
    1 Error(s)

Time Elapsed 00:00:00.75

Why does the build still report a warning wave 7 error?
https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/warning-waves#cs8981---the-type-name-only-contains-lower-cased-ascii-characters

I expected warning wave 7 to be disabled by setting AnalysisLevel to none in my csproj ❓

The warning disappears when I run dotnet build --no-incremental /p:WarningLevel=6 or lower.

Page URL

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-options/errors-warnings#analysis-level

Content source URL

https://github.com/dotnet/docs/blob/main/docs/csharp/language-reference/compiler-options/errors-warnings.md

Document Version Independent Id

e57ac82b-307e-163b-8172-52644b3a6baa

Article author

@BillWagner

Metadata

• ID: 26ef35c2-6df4-26f8-32b2-9b50eb76c037
• Service: dotnet-csharp
• Sub-service: lang-reference

[sliekens]

The MSBuild code which sets WarningLevel based on AnalysisLevel:

https://github.com/dotnet/sdk/blob/36bea1315b44a957c274dc4b4e4b51c2e5c1c651/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.Analyzers.targets#L58-L65

All I can really see is that AnalysisLevel=preview results in /warn:9999 but otherwise the warn level is derived from the TFM, e.g. TargetFramework=net8.0 results in /warn:8.

Given this information, the warning level table is outdated, because 4 hasn't been the default warn level since .NET 5 which is when they started computing it based on TFM.

[sliekens]

Update: I tracked it down to a product bug / regression. The code that sets the WarningLevel to match the AnalysisLevel was removed in dotnet/sdk#24826

[cremor]

Related: #33559

[BillWagner]

Thanks for tracking this down @sliekens

I've added it to our backlog to update when we next update this article.