`PathUtility.HasExtension` doesn't correctly consider case sensitivity of file system

[Youssef1313]

sdk/src/Cli/Microsoft.DotNet.Cli.Utils/PathUtility.cs

Lines 341 to 346 in 5ac3352

	var comparison = StringComparison.Ordinal;
	if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
	{
	comparison = StringComparison.OrdinalIgnoreCase;
	}

Only Windows is considered case insensitive, but looks like MacOS is also case insensitive.

I very much recall I have seen code somewhere in dotnet org that tries to create a dummy file, and then calls File.Exists with different casing to determine whether the file system is case sensitive and handle some potential edge cases, but I can't recall where that is.

[KalleOlaviNiemitalo]

On macOS, one can create a HFS file system as case-sensitive or case-insensitive. Not sure about APFS.

On Windows, individual directories in NTFS can be set as case-sensitive or case-insensitive; and the case folding table is stored in the file system so it might not match the version of Unicode in the operating system. Not sure about ReFS.

[KalleOlaviNiemitalo]

I very much recall I have seen code somewhere in dotnet org that tries to create a dummy file, and then calls File.Exists with different casing to determine whether the file system is case sensitive and handle some potential edge cases, but I can't recall where that is.

There is code like that at https://github.com/dotnet/msbuild/blob/bcc2dc6a6509ffb63f1253a9bbbaaa233bd53a50/src/Shared/FileUtilities.cs#L69-L91 and the comment there links to https://github.com/dotnet/runtime/blob/73ba11f3015216b39cb866d9fb7d3d25e93489f2/src/libraries/Common/src/System/IO/PathInternal.CaseSensitivity.cs#L41-L59

[nagilson]

That's a good point, seems like this should be done. We'd accept a PR for this for sure, thank you to @KalleOlaviNiemitalo for linking the relative code.

My main concern is the priority: This seems like it could create all sorts of hard to detect bugs. Although it doesn't seem to have been linked to a problem ever before. And its possible fixing this will uncover new problems/reliance on existing bad behavior which could become a lot of work, even though the change is relatively simple. Will discuss with the team.