[Lucene.Net] Repro if LUCENENET-54 (ArgumentOutOfRangeException in SnowballProgram)

[Simon Svensson]

Hi,

I've written a simple reproduction of LUCENENET-54 
(ArgumentOutOfRangeException in SnowballProgram). I'm not sure about the 
correct workflow to reopen this issue (it was closed as invalid in 2007 
due to missing information), so I'm throwing what I got into the 
developer mailing list and hope that someone else knows the correct 
approach. Problem originates in SnowballProgram.slice_to, where the 
second argument to StringBuilder.ToString(start, length) where the last 
parameter is passed an index instead of the length.

Reproduction:
using System.IO;
using Lucene.Net.Analysis.Snowball;
using Lucene.Net.Analysis.Tokenattributes;
using NUnit.Framework;

namespace ConsoleApplication {
    [TestFixture]
    public class LuceneRepo {
        [Test(Description = "LUCENENET-54")]
        public void Repro() {
            var analyzer = new SnowballAnalyzer("Finnish");

            var input = new StringReader("terve");
            var tokenStream = analyzer.TokenStream("fieldName", input);
            var termAttr = 
(TermAttribute)tokenStream.AddAttribute(typeof (TermAttribute));

            Assert.That(tokenStream.IncrementToken(), Is.True);
            Assert.That(termAttr.Term(), Is.EqualTo("terv"));
        }
    }
}

Unexpected exception:
System.ArgumentOutOfRangeException: Index and length must refer to a 
location within the string.
Parameter name: length
   at System.Text.StringBuilder.ToString(Int32 startIndex, Int32 length)
   at SF.Snowball.SnowballProgram.slice_to(StringBuilder s) in 
C:\Dev\Third 
Party\Lucene.NET\src\contrib\Snowball\SF\Snowball\SnowballProgram.cs:line 467
   at SF.Snowball.Ext.FinnishStemmer.r_tidy() in C:\Dev\Third 
Party\Lucene.NET\src\contrib\Snowball\SF\Snowball\Ext\FinnishStemmer.cs:line 
974
   at SF.Snowball.Ext.FinnishStemmer.Stem() in C:\Dev\Third 
Party\Lucene.NET\src\contrib\Snowball\SF\Snowball\Ext\FinnishStemmer.cs:line 
1137

Expected result:
The unit test should pass.

// Simon