[Lucene.Net] [jira] [Commented] (LUCENENET-414) The definition of CharArraySet is dangerously confusing and leads to bugs when used.

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

    [ https://issues.apache.org/jira/browse/LUCENENET-414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13097325#comment-13097325 ] 

Digy commented on LUCENENET-414:
--------------------------------

I think the simplest solution for 2.9.4 will be adding
{code}
        //
        public virtual bool Add(object key, object value)
        {
            if (key is string)
                return Add((string)key);
            else if (key is char[])
                return Add((char[])key);
            return false;
        }

{code}
to CharArraySet

DIGY

> The definition of CharArraySet is dangerously confusing and leads to bugs when used.
> ------------------------------------------------------------------------------------
>
>                 Key: LUCENENET-414
>                 URL: https://issues.apache.org/jira/browse/LUCENENET-414
>             Project: Lucene.Net
>          Issue Type: Bug
>          Components: Lucene.Net Core
>    Affects Versions: Lucene.Net 2.9.2
>         Environment: Irrelevant
>            Reporter: Vincent Van Den Berghe
>            Priority: Minor
>             Fix For: Lucene.Net 2.9.4, Lucene.Net 2.9.4g
>
>
> Right now, CharArraySet derives from System.Collections.Hashtable, but doesn't actually use this base type for storing elements.
> However, the StandardAnalyzer.STOP_WORDS_SET is exposed as a System.Collections.Hashtable. The trivial code to build your own stopword set using the StandardAnalyzer.STOP_WORDS_SET and adding your own set of stopwords like this:
> CharArraySet myStopWords = new CharArraySet(StandardAnalyzer.STOP_WORDS_SET, ignoreCase: false);
> foreach (string domainSpecificStopWord in DomainSpecificStopWords)
>     stopWords.Add(domainSpecificStopWord);
> ... will fail because the CharArraySet accepts an ICollection, which will be passed the Hashtable instance of STOP_WORDS_SET: the resulting myStopWords will only contain the DomainSpecificStopWords, and not those from STOP_WORDS_SET.
> One workaround would be to replace the first line with this:
> CharArraySet stopWords = new CharArraySet(StandardAnalyzer.STOP_WORDS_SET.Count + DomainSpecificStopWords.Length, ignoreCase: false);
> foreach (string domainSpecificStopWord in (CharArraySet)StandardAnalyzer.STOP_WORDS_SET)
>     stopWords.Add(domainSpecificStopWord);
> ... but this makes use of the implementation detail (the STOP_WORDS_SET is really an UnmodifiableCharArraySet which is itself a CharArraySet). It works because it forces the foreach() to use the correct CharArraySet.GetEnumerator(), which is defined as a "new" method (this has a bad code smell to it)
> At least 2 possibilities exist to solve this problem:
> - Make CharArraySet use the Hashtable instance and a custom comparator, instead of its own implementation.
> - Make CharArraySet use HashSet<char[]>, defined in .NET 4.0.

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