.editorconfig fails to suppress analyzer warnings

[AArnott]

Version Used: .NET Core SDK 3.1.201, VS 16.6.0 Preview 3 (29923.206.master)

Steps to Reproduce:

git clone https://github.com/AArnott/Nerdbank.Streams.git
cd Nerdbank.Streams
git checkout f5c2933e0b66b2a2ad7415c5d637ba5149d5370b
dotnet build src\Nerdbank.Streams

Expected Behavior:

No warnings for files under the ext directory.

Actual Behavior:

Many dozens of warnings under the ext\MessagePack\src\MessagePack.UnityClient\Assetes\Scripts\MessagePack direcotry.

The ext folder is where submodules are mounted, and while these add compilation inputs to the C# compiler, we can't hold them to the same style bar that our the parent repo is held to. For this reason, I have an ext\.editorconfig file that turns off all analyzers. But although I can see all the relevant .editorconfig files are passed to the compiler, the analyzers run and produce many warnings anyway.

[AArnott]

Note that the VS in-proc compiler seems to do it right -- it doesn't produce these warnings in the error list except right after a full project build, and then when I navigate to those warnings in the editor, they disappear. So it seems it's just a bug in the out of proc (or command line) build.

[AArnott]

Note if I move the content of ext\.editorconfig into the repo root .editorconfig file, the warnings go away.

[AArnott]

This repros with the very latest compiler as well:

<PackageReference Include="Microsoft.Net.Compilers.Toolset" Version="3.6.0-1.final" PrivateAssets="all" />

[jcouv]

Tagging @agocke

[ssa3512]

I think I am running into a similar issue - trying to turn on some of the analyzers for my project. I added the following to .editorconfig in the root of our repository. Building locally has the expected results (no errors/no CAxxxx warnings, except for CA1824 which may be a separate issue). Our Azure DevOps hosted CI build is giving lots of CA warnings despite the editorconfig

.editorconfig:

# CA1827: Do not use Count/LongCount when Any can be used
dotnet_diagnostic.CA1827.severity = error

# CA1829: Use Length/Count property instead of Count() when available
dotnet_diagnostic.CA1829.severity = error

# Default severity for all analyzer diagnostics
dotnet_analyzer_diagnostic.severity = none

Edit: It appears this maybe version specific. I get the warnings in VS 16.7, but not in 16.8 Preview 4. Presumably the CI server isn't using a preview VS version, hence not respecting the .editorconfig