Roslyn unable to load analyzer configs if disk letter in path of current directory is not matching file name in analyzerconfig option

[ghisguth]

Version Used:

Microsoft (R) Visual C# Compiler version 3.8.0-5.20604.10 (9ed4b774)

Steps to Reproduce:

1. Open command line. Go to directory with .editorconfig. Be sure to change directory using lowercase for drive. E.g. cd c:\Src\Foo\Bar\
2. Create analyzer config in c:\Src\Foo.editorconfig
3. Execute csc.exe with /analyzerconfig:C:\Src\Foo\.editorconfig (Note disk letter is upper case C:)

Expected Behavior:

Roslyn will load editor config and apply to all files in c:\Src\Foo\Bar\

Actual Behavior:

Roslyn ignores the config for analyzers.

Details:

• Roslyn loads base directory using Directory.GetCurrentDirectory(). https://github.com/dotnet/roslyn/blob/26939574c8e180d5135b2a28f183709b67483634/src/Compilers/Shared/BuildClient.cs#L92
• All source files will have base path appended in ParseFileArgument: https://github.com/dotnet/roslyn/blob/52b08d4f4c2895a2d39a0429d82317775b814754/src/Compilers/Core/Portable/CommandLine/CommandLineParser.cs#L953
• AnalyzerConfig will load file as is and store NormalizedDirectory with the same casing it was passed. https://github.com/dotnet/roslyn/blob/8e23563ca8ce49f2f61bea49178cae141605edae/src/Compilers/Core/Portable/CommandLine/AnalyzerConfig.cs#L150-L151
• AnalyzerConfigSet.GetOptionsForSourcePath will use StartsWith with StringComparison.Ordinal to check if c# file belongs to base directory of the config. So if casing of base directory and analyzerconfig option is not matching, it will not apply analyzer configs to it. https://github.com/dotnet/roslyn/blob/8e23563ca8ce49f2f61bea49178cae141605edae/src/Compilers/Core/Portable/CommandLine/AnalyzerConfigSet.cs#L213-L217

Visual Studio impact:

if you open csproj via solution. Visual studio will lowercase disk in path of the csproj and while compile all paths will start from lowercase (e.g. c:\Src\Foo\Bar\Bar.csproj). analyzerconfig option will work as expected.

If you open csproj directly and try to compile. Visual studio will open it with disk as upper case (e.g. C:\Src\Foo\Bar\Bar.csproj). And analyzer config will be ignored.

[ghisguth]

• @jasonmalinowski FYI. Seems like either either string comparison should be case insensitive. Or normalized path should always lowercase disk letter if it is present.

[jasonmalinowski]

@ghisguth Thanks for the detailed analysis here; we'll have to process this one to figure out which layers will need a fix here!

[jaredpar]

I don't think this discussion is only limited to /analyzerConfig. Consider that for options like /pathMap we also treat the argument literally and do no normalization on it.

How we handle file path casing is an aspect of the compiler that I don't think we have an explicit documented plan on. This is likely a good time to do that and add a bit of consistency to how we do it. The general approach we've used to the best of my recollection is:

• Basic path normalization on arguments to the command line. That can include anything from removing trailing slashes on directories, getting consistent casing for drive letters, etc ...
• All other parts of the compiler treat paths as ordinal ignore case.

@chsienki @mavasani @tmat for feedback here as well.