SpecFlow: Opening a feature file result in a NullReferenceException

Question

Since a couple of weeks I suddenly have issues with the SpecFlow extension in Visual Studio 2019 (professional edition). Out of the blue it stopped working. First I thought because of an update of VS, but other colleagues of mine are using the same (latest) version of VS and for them SpecFlow works.

The problems I'm experiencing are:

No settings menu for SpecFlow (Tools - Options - SpecFlow)
A NullReferenceException when opening a feature file (see end of post for entry of activity log)
When feature file is opened no syntax highlighting
No context menu

The test explorer is still discovering the tests and I can still run them, but not from the feature file (neither debugging the steps).

The extension is installed and enabled correctly (as far as I can tell). Already tried the following without success:

Uninstall and install the SpecFlow for Visual Studio 2019 extension
Uninstall SpecFlow and install Deveroom
Uninstall Visual Studio 2019 and install again

Any of you have any idea on what might be causing this?

Activity log entry

<entry>
  <record>806</record>
  <time>2021/02/09 09:25:56.786</time>
  <type>Error</type>
  <source>Editor or Editor Extension</source>
  <description>System.NullReferenceException: Object reference not set to an instance of an object.&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.ProjectScopeFactory.&lt;.ctor&gt;b__9_0() in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\ProjectScopeFactory.cs:line 52&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.Implementation.Utils.SynchInitializedInstance`1.EnsureInitialized()&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.ProjectScopeFactory.&lt;.ctor&gt;b__9_2(Project project) in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\ProjectScopeFactory.cs:line 64&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.Implementation.Utils.SynchronizedResultCache`3.GetOrCreate(TSource source)&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.ProjectScopeFactory.GetProjectScope(Project project) in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\ProjectScopeFactory.cs:line 76&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.GherkinLanguageServiceFactory.CreateLanguageService(ITextBuffer textBuffer) in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\GherkinLanguageServiceFactory.cs:line 51&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.GherkinLanguageServiceFactory.&lt;&gt;c__DisplayClass7_0.&lt;GetLanguageService&gt;b__0() in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\GherkinLanguageServiceFactory.cs:line 43&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.GherkinBufferServiceManager.&lt;&gt;c__DisplayClass3_0`1.&lt;GetOrCreate&gt;b__0() in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\GherkinBufferServiceManager.cs:line 32&#x000D;&#x000A;
    at Microsoft.VisualStudio.Utilities.PropertyCollection.GetOrCreateSingletonProperty[T](Object key, Func`1 creator)&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.GherkinBufferServiceManager.GetOrCreate[TService](ITextBuffer textBuffer, Func`1 creator) in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\GherkinBufferServiceManager.cs:line 29&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.GherkinLanguageServiceFactory.GetLanguageService(ITextBuffer textBuffer) in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\GherkinLanguageServiceFactory.cs:line 43&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.GherkinFileEditor.GherkinFileClassifierProvider.&lt;&gt;c__DisplayClass3_0.&lt;GetClassifier&gt;b__0() in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\GherkinFileEditor\GherkinFileClassifierProvider.cs:line 31&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.GherkinBufferServiceManager.&lt;&gt;c__DisplayClass3_0`1.&lt;GetOrCreate&gt;b__0() in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\GherkinBufferServiceManager.cs:line 32&#x000D;&#x000A;
    at Microsoft.VisualStudio.Utilities.PropertyCollection.GetOrCreateSingletonProperty[T](Object key, Func`1 creator)&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.LanguageService.GherkinBufferServiceManager.GetOrCreate[TService](ITextBuffer textBuffer, Func`1 creator) in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\LanguageService\GherkinBufferServiceManager.cs:line 29&#x000D;&#x000A;
    at TechTalk.SpecFlow.VsIntegration.GherkinFileEditor.GherkinFileClassifierProvider.GetClassifier(ITextBuffer buffer) in D:\a\1\s\TechTalk.SpecFlow.VSIXShared\GherkinFileEditor\GherkinFileClassifierProvider.cs:line 30&#x000D;&#x000A;
    at Microsoft.VisualStudio.Text.Classification.Implementation.ClassifierTaggerProvider.&lt;&gt;c__DisplayClass12_0`1.&lt;CreateTagger&gt;b__0(IClassifierProvider provider)&#x000D;&#x000A;
    at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.InvokeEligibleFactories[TExtensionInstance,TExtensionFactory,TMetadataView](IEnumerable`1 lazyFactories, Func`2 getter, IContentType dataContentType, IContentTypeRegistryService contentTypeRegistryService, Object errorSource)&#x000D;&#x000A;--- End of stack trace from previous location where exception was thrown ---&#x000D;&#x000A;
    at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject)
  </description>
</entry>

Edited: After running a repair of VS I could see the menu option for the 'Clear MEF Component Cache' extension. Unfortunately using this got me no further with the SpecFlow extension (still the same issues).

I half wonder if deleting stuff in C:/Users/%USERNAME%/AppData/*/Microsoft/Visual Studio/{Version}/ComponentModelCache/ would do the trick as well. — Greg Burghardt
Neither deleting the stuff in this folder nor installing the MEF cache cleaner worked. — Eddie Terlouw

Andreas Willich Andreas Willich · Accepted Answer · 2021-02-16T12:05:22

This looks like the MEF cache of Visual Studio has a problem.
An easy way to clean it is the Clear MEF Component Cache extension from Mads Kristensen. It can be found on the marketplace here: https://marketplace.visualstudio.com/items?itemName=MadsKristensen.ClearMEFComponentCache

Install it and after a restart of VS, execute the command in the menu:

After that, restart VS again and the SpecFlow VS Extension should work again.

SpecFlow: Opening a feature file result in a NullReferenceException

2 Answers