Remove unnecessary imports analyzer is significantly slowing builds (11% CPU time)

[Youssef1313]

@mavasani How can this be disabled? I already have dotnet_diagnostic.IDE0005.severity = none in .globalconfig file.

[lonix1]

What tool is that?

[Youssef1313]

@lonix1 The one in the screenshot? It is PerfView.

[sharwell]

@Youssef1313 I think this may be a red herring. The analyzer does almost no actual work. It just instructs the compiler to complete work it would already complete, and then then waits for that work to finish. If this analyzer has any impact on the total time it takes to complete a build for the case where there are no IDE0005 diagnostics reported, it is an indicator that the diagnostics and/or binding cache in the compiler is broken.

[Youssef1313]

@sharwell This was solely through binlog times and profiling with PerfView. I agree that likely the total time may not be affected. It indeed looks like a cost that "moved" from the compiler to the analyzer.

The remaining issue here will still be why it's running even with dotnet_diagnostic.IDE0005.severity = none

[sharwell]

@Youssef1313 it's running because the following line incorrectly sets hasAnyCodeStyleOption to true:

roslyn/src/Analyzers/Core/Analyzers/RemoveUnnecessaryImports/AbstractRemoveUnnecessaryImportsDiagnosticAnalyzer.cs

Line 31 in cecdb80

RemoveUnnecessaryImportsConstants.DiagnosticFixableId, EnforceOnBuild.Never, hasAnyCodeStyleOption: true, "", "", isConfigurable: false);