Unhandled System.ArgumentException in LoadCachedAnalysis

[rkavalap]

<entry>
    <record>96225</record>
    <time>2015/10/05 18:02:16.567</time>
    <type>Error</type>
    <source>Node.js Tools for Visual Studio</source>
    <description>
    Unhandled exception in LoadCachedAnalysis (F:\72\src\Nodejs\Product\Nodejs\Intellisense\VsProjectAnalyzer.cs:1404);
    System.ArgumentException: Source array was not long enough. Check srcIndex and length, and the array's lower;   
    at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable);   
    at Microsoft.NodejsTools.Analysis.Deque`1.GrowArray();   
    at Microsoft.NodejsTools.Analysis.Deque`1.Append(T x);   
    at Microsoft.NodejsTools.Analysis.AnalysisLog.Add(String Event, Object[] Args);   
    at Microsoft.NodejsTools.Analysis.AnalysisLog.NewUnit(AnalysisUnit unit);   
    at Microsoft.NodejsTools.Analysis.AnalysisUnit..ctor(Statement ast, JsAst tree, EnvironmentRecord environment);   
    at Microsoft.NodejsTools.Analysis.JsAnalyzer.&lt;&gt;c__DisplayClass30_1.&lt;AddPackageJson&gt;b__0(String dependency);   
    at System.Linq.Enumerable.WhereSelectListIterator`2.MoveNext();   
    at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection);   
    at Microsoft.NodejsTools.Analysis.JsAnalyzer.AddPackageJson(String filePath, String entryPoint, List`1 dependencies);   
    at Microsoft.NodejsTools.Intellisense.VsProjectAnalyzer.AddPackageJson(String path, String mainFile, List`1 dependencies);   
    at Microsoft.NodejsTools.Intellisense.VsProjectAnalyzer.&lt;&gt;c__DisplayClass55_0.&lt;AddPackageJson&gt;b__0();   
    at Microsoft.NodejsTools.Intellisense.VsProjectAnalyzer.&lt;&gt;c__DisplayClass108_2.&lt;LoadCachedAnalysis&gt;b__0();   
    at System.Threading.Tasks.Task.InnerInvoke();   
    at System.Threading.Tasks.Task.Execute();
    --- End of stack trace from previous location where exception was thrown ---;   
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task);   
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task);   
    at Microsoft.VisualStudioTools.VsTaskExtensions.&lt;HandleAllExceptions&gt;d__4.MoveNext()
    </description>
  </entry>

[mousetraps]

I can't reproduce this issue, but nothing about GrowArray looks suspicious, so the problem likely lies elsewhere. Deque.cs itself hasn't changed in a while (and has also been shipping with PTVS for a while longer, so I would have expected them to run into this issue at some point if it was indeed an issue with the Deque logic... or at the very least we're likely using it in some unintended manner here).

This looks related to #522, which has a very similar stack trace. In both cases, the issue appears to occur when creating the RequireAnalysisUnit:
https://github.com/Microsoft/nodejstools/blob/05b51f5e034f4907418ba4bd851816726d0ba1d4/Nodejs/Product/Analysis/Analysis/JsAnalyzer.cs#L150

There doesn't appear to be anything suspicious about the Select method...
http://referencesource.microsoft.com/#System.Core/System/Linq/Enumerable.cs,372

So I believe in this case, we're entering a state where we are simultaneously mutating the AnalysisLog from this thread and from the analysis thread (e.g. in the case of #522... we were probably in the middle of AnalysisLog.GrowArray from the analysis thread, and AnalysisLog.Append from this thread), which is caused the AnalysisLog properties like _data, _tail, etc. to get out of sync with one another.