Microsoft.AspNetCore.Mvc.Analyzers.TopLevelParameterNameAnalyzer threw NullReferenceException

[sunildixit]

I am using VS 2019 Preview 16.3.0 Preview 1.0

I have two webapps in the solution and for both of them I am always getting the warning described below

Warning AD0001 Analyzer 'Microsoft.AspNetCore.Mvc.Analyzers.TopLevelParameterNameAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. ConnectorApp.Web 1 Active Analyzer 'Microsoft.AspNetCore.Mvc.Analyzers.TopLevelParameterNameAnalyzer' threw the following exception:

Exception occurred with following context:
Compilation: ConnectorApp.Web
ISymbol: Create (Method)
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.CodeAnalysis.CodeAnalysisExtensions.IsAssignableFrom(ITypeSymbol source, ITypeSymbol target)
at Microsoft.CodeAnalysis.CodeAnalysisExtensions.d__2.MoveNext()
at Microsoft.CodeAnalysis.CodeAnalysisExtensions.d__4.MoveNext()
at System.Linq.Enumerable.Any[TSource](IEnumerable1 source) at Microsoft.AspNetCore.Mvc.Analyzers.TopLevelParameterNameAnalyzer.<>c__DisplayClass3_0.b__0(SymbolAnalysisContext symbolAnalysisContext) at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.<>c.b__43_1(ValueTuple2 data)
at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteAndCatchIfThrows_NoLock[TArg](DiagnosticAnalyzer analyzer, Action1 analyze, TArg argument, Nullable1 info)

[pranavkm]

@sunildixit could you include the obj\project.assets.json? The last time somebody ran in to this was because they had a mix of 3.0 and 2.2 packages in their application

[sunildixit]

Here's the file.
project.assets.txt

[pranavkm]

Thanks. Could you also link your project file? The assets file suggests some fairly odd dependencies - it's a bit difficult to tell how you got there just inspecting it.

[sunildixit]

Here you go.
ConnectorApp.Web.txt

[pranavkm]

Thanks @sunildixit. It's clearly not the same issue as #8686 so this does need further investigation since it's not entirely obvious where the null ref is. If you happen to have a simple app to repro the problem, that'd be great.

@JunTaoLuo looking at the project.assets.json, would you know why the app's picking up references to Kestrel 1.0, Hosting 1.0 etc? Shouldn't the shared runtime override the values here?

[sunildixit]

I think I found one issue. The MVC analyzer was not installed on the MVCApp. I am not sure how to explain how this error cropped up then. But after I explicitly installed the analyzer on the web projects, then the error went away.

[mynkow]

This happens to me as well. The scenario is that I have a project on core 2.2 and a branch updating to 3.0. When I switch branches this happens.

[pranavkm]

@mynkow could you please file a new issue with a minimal repro? Thanks.