Editorconfig severity changes not respected

[mavasani]

Version Used: Latest 16.8 P2 dogfood build

Steps to Reproduce:

1. Create a new C# class library project with below source code and verify IDE0051 reported for M:

class C
{
    void M() { }
}

2. Add an .editorconfig manually file at root of the project with following contents:

[*.cs]

dotnet_diagnostic.IDE0051.severity = warning

3. Switch back to the source file and see the diagnostics/squiggles on M

Expected Behavior:
IDE0051 warning in error list and a squiggle for the same in the editor

Actual Behavior:
IDE0051 is still a message and there is no squiggle.

4. Keep editing the source file, say renaming M to M2, renaming the containing type, adding more code, etc.

Expected Behavior:
.editorconfig dotnet_diagnostic should take effect at least after doing some source code edits.

Actual Behavior:
IDE0051 is still a message and there is no squiggle. The diagnostic correctly gets updated to say M2 instead of M, so diagnostics are not stale - just the fact that new editorconfig settings are not being applied at all. Only way to get these applied are to close and re-open/reload the project.

[mavasani]

I verified that issue started happening after #44331. It does not repro on 16.8 P2 builds prior to that change getting merged. @jasonmalinowski can you take a look? I'll try to work on an integration test to repro this behavior.

[sharwell]

I observed this as well when testing from the master branch.

[mavasani]

I was able to write an integration test for this regression: #46794