[jira] [Created] (LUCENE-8723) Bad interaction bewteen WordDelimiterGraphFilter, StopFilter and FlattenGraphFilter

["Nicolás Lichtmaier (JIRA)" <ji...@apache.org>]

Nicolás Lichtmaier created LUCENE-8723:
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             Summary: Bad interaction bewteen WordDelimiterGraphFilter, StopFilter and FlattenGraphFilter
                 Key: LUCENE-8723
                 URL: https://issues.apache.org/jira/browse/LUCENE-8723
             Project: Lucene - Core
          Issue Type: Bug
          Components: modules/analysis
    Affects Versions: 7.7.1
            Reporter: Nicolás Lichtmaier


I was debugging an issue (missing tokens after analysis) and when I enabled Java assertions I uncovered a bug when using WordDelimiterGraphFilter + StopFilter + FlattenGraphFilter.

I could reproduce the issue in a small piece of code. This code gives an assertion failure when assertions are enabled (-ea java option):

{code:java}
    Builder builder = CustomAnalyzer.builder();
    builder.withTokenizer(StandardTokenizerFactory.class);
    builder.addTokenFilter(WordDelimiterGraphFilterFactory.class, "preserveOriginal", "1");
    builder.addTokenFilter(StopFilterFactory.class);
             
    builder.addTokenFilter(FlattenGraphFilterFactory.class);}}
    Analyzer analyzer = builder.build();}}
     
    TokenStream ts = analyzer.tokenStream("*", new StringReader("x7in"));
    ts.reset();
    while(ts.incrementToken())
        ;
{code}

This gives:

{code}
Exception in thread "main" java.lang.AssertionError: 2
     at org.apache.lucene.analysis.core.FlattenGraphFilter.releaseBufferedToken(FlattenGraphFilter.java:195)
     at org.apache.lucene.analysis.core.FlattenGraphFilter.incrementToken(FlattenGraphFilter.java:258)
     at com.wolfram.textsearch.AnalyzerError.main(AnalyzerError.java:32)
{code}

Maybe removing stop words after WordDelimiterGraphFilter is wrong, I don't know. However is the only way to process stop-words generated by that filter. In any case, it should not eat tokens or produce assertions. 



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