RedundantPrivateCodeFixProvider passes null document in DocumentChangeAction.PostProcessChangesAsync

jmarolf commented 9 years ago

Customer reported a stacktrace at https://github.com/dotnet/roslyn/issues/5121.

Object reference not set to an instance of an object.&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.Simplification.Simplifier.&lt;ReduceAsync&gt;d__11.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at RefactoringEssentials.DocumentChangeAction.&lt;PostProcessChangesAsync&gt;d__6.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.CodeActions.CodeAction.&lt;PostProcessChangesAsync&gt;d__14.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.CodeActions.CodeAction.&lt;PostProcessAsync&gt;d__13.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.CodeActions.CodeAction.&lt;GetPreviewOperationsAsync&gt;d__6.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.SuggestedAction.&lt;&gt;c__DisplayClass10_0.&lt;&lt;GetPreviewOperationsAsync&gt;b__0&gt;d.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.SuggestedAction.&lt;GetPreviewResultAsync&gt;d__14.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.SuggestedAction.&lt;&gt;c__DisplayClass17_0.&lt;&lt;GetPreviewAsync&gt;b__0&gt;d.MoveNext()&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;   
at Microsoft.CodeAnalysis.Extensions.IExtensionManagerExtensions.&lt;PerformFunctionAsync&gt;d__3`1.MoveNext()

My plan is to make sure the Simplifier throws ArgumentNull exceptions so this is easier to track down, but let me know if you have other suggestions.

Rpinski commented 9 years ago

Hmm, I'm still wondering how this can happen. The Document instance we pass here is something we receive from Roslyn (it's an overridden method):

https://github.com/icsharpcode/RefactoringEssentials/blob/master/RefactoringEssentials/CSharp/Diagnostics/DocumentChangeAction.cs#L39

Wouldn't that mean that Roslyn has passed a null reference to us?

Rpinski commented 9 years ago

And I also don't see in our code, where we could create a null Document in this analyzer:

https://github.com/icsharpcode/RefactoringEssentials/blob/master/RefactoringEssentials/CSharp/Diagnostics/Custom/RedundantPrivateCodeFixProvider.cs#L38

https://github.com/icsharpcode/RefactoringEssentials/blob/master/RefactoringEssentials/CSharp/Diagnostics/Custom/RedundantPrivateAnalyzer.cs#L151

icsharpcode / RefactoringEssentials

RedundantPrivateCodeFixProvider passes null document in DocumentChangeAction.PostProcessChangesAsync #105