[GitHub] [lucenenet] rclabo commented on issue #527: ArgumentNullException with BlendedInfixSuggester (v. 4.8.0-beta00014)

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rclabo commented on issue #527:
URL: https://github.com/apache/lucenenet/issues/527#issuecomment-947038717


   I am able to reproduce the `Exception` @monco83  is observing based on the code provided.  @NightOwl888  turned that code into a unit test and that test does throw with the same stacktrace @monco83 is seeing.
   
   The next question that @NightOwl888  and I had was whether this was a issue introduced when the Java version of Lucene 4.8 was ported to C# and .NET.  To investigate this @NightOwl888 and I ported that failing unit test to Java and ran the unit test against Java Lucene 4.8 on my machine.  I can confirm that it fails the same way in Java so this is not a porting bug.
   
   When running the unit test in java (or c#) the line highlighted below is hit three time, the first two times `docTerm` is `b` or `c` and `prefixToken` is null.  These cases continue on without an `Exception`.  But the third time this line is hit, `docTerm` is `d` and `prefixToken` is null.  since `matchedTokens` contains only `b` and `c` the `startsWith` method is evaluated and produces the error.  Again this happens in both Java Lucene 4.8 and Lucene.NET 4.8.  
   
   ![image](https://user-images.githubusercontent.com/6945499/137975637-4f4f6764-f242-43e8-a009-6761cc53ea73.png)
   
   Unfortunately neither @NightOwl888  or myself have intimate knowledge of the high level workings of `BlendedInfixSuggester` so we do not currently know whether this is a bug in Lucene 4.8 or whether the class is not being used correctly.  @NightOwl888  located this document https://sease.io/2018/06/apache-lucene-blendedinfixsuggester-how-it-works-bugs-and-improvements.html which describes 3 bugs in the Suggester and workarounds, but it isn't clear any of them are this issue.
   
   At this point, since we have verified it's not a bug in the porting of Lucene to .NET it'd be great if @monco83 can do a little digging to see if perhaps there is an issue with how  `BlendedInfixSuggester` is being called/used.  We will leave this issue open, so the findings can be reported back.
   


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