Implement the ModuleInitializerAttributeShouldNotBeUsedInLibraries analyzer

[jeffhandley]

Fixes dotnet/runtime#43328 by raising a diagnostic any time the [ModuleInitializer] attribute is applied to a method (in conformance with the C# language feature that supports this attribute).

Per the API review of this analyzer, the analyzer will be defaulted to on as a warning.

[Youssef1313]

The analyzer doesn't really check whether we're in a library or not.
So the false positive rate can be high.

[jeffhandley]

The analyzer doesn't really check whether we're in a library or not.
So the false positive rate can be high.

We expect the [ModuleInitializer] attribute to be used very rarely, so we can tolerate a level of false positives.

Is it possible to check if the type is in a class library assembly?

[Youssef1313]

The analyzer doesn't really check whether we're in a library or not.
So the false positive rate can be high.

We expect the [ModuleInitializer] attribute to be used very rarely, so we can tolerate a level of false positives.

Is it possible to check if the type is in a class library assembly?

Yeah I think it's possible: if (context.Compilation.Options.OutputKind != OutputKind.DynamicallyLinkedLibrary) return;

[jeffhandley]

Yeah I think it's possible: if (context.Compilation.Options.OutputKind != OutputKind.DynamicallyLinkedLibrary) return;

Thanks! This will still allow the analyzer to run for web and mobile apps I presume, but it will remove false positives from console apps and windows apps, so that's still an improvement.

[Youssef1313]

This will still allow the analyzer to run for web and mobile apps I presume

I think it won't run for web apps. Not sure about mobile.

[jeffhandley]

Thanks for the thorough review, @Youssef1313! I've addressed all of your feedback if you want to take another look.

[jeffhandley]

I forgot to run msbuild /t:Pack on that commit. I'm correcting the resource strings and running that command, which should fix the build.

[codecov]

Codecov Report

Merging #5347 (d7a7799) into release/6.0.1xx (92cc133) will increase coverage by 0.01%.
The diff coverage is 98.34%.

@@                 Coverage Diff                 @@
##           release/6.0.1xx    #5347      +/-   ##
===================================================
+ Coverage            95.60%   95.62%   +0.01%     
===================================================
  Files                 1236     1238       +2     
  Lines               283895   284725     +830     
  Branches             17032    17083      +51     
===================================================
+ Hits                271414   272261     +847     
+ Misses               10179    10157      -22     
- Partials              2302     2307       +5     

[buyaa-n]

Left few NITs overall looks good, thanks!