fix: warning as errror CS8669 on csharp generated file

[tomflenner]

Description

When using the OpenFeature CLI code generator for C# in projects that have "warnings as errors" enabled, the generated code produces a compilation error.

Error

1>OpenFeature.g.cs(535,84): Error CS8669 :The annotation for Nullable reference types must only be used in code within a '#nullable' annotations context. Automatically generated code requires an explicit '#nullable' directive in the source.

Steps to Reproduce

1. Create a C# project with <TreatWarningsAsErrors>true</TreatWarningsAsErrors> in the .csproj file
2. Generate C# code using the OpenFeature CLI code generator
3. Attempt to build the project
4. Observe the CS8669 compilation error in the generated OpenFeature.g.cs file

Repro : https://github.com/tomflenner/openfeature-cli-sharp-repro

Expected Behavior

The generated code should compile without errors, even in projects with warnings as errors enabled.

Proposed Solution

Add #nullable enable directive at the top of the generated C# file (OpenFeature.g.cs). This will provide the explicit nullable context required by the compiler.

Workaround

Used this rules in my .editorconfig :

[**/*.g.cs]
generated_code = true
# Disable nullable reference type warnings in generated code
dotnet_diagnostic.CS8669.severity = none

[tomflenner]

@askpt 👋🏻,

I think you might have nice opinion on this ! I can pickup this task 👍🏻

[askpt]

@askpt 👋🏻,

I think you might have nice opinion on this ! I can pickup this task 👍🏻

👋 @tomflenner

That is correct, if the nullable annotations are added in a non-nullable context it would produce warnings which then will be errors with that compilation flag enabled. I believe your proposed solution is a valid one.

Adding #nullable enable at the top of the class is the best approach.

[tomflenner]

/assign Happy to take this issue !