RegexQuery matches terms the input regex doesn't actually match
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                 Key: LUCENE-1683
                 URL: https://issues.apache.org/jira/browse/LUCENE-1683
             Project: Lucene - Java
          Issue Type: Improvement
          Components: contrib/*
    Affects Versions: 2.3.2
            Reporter: Trejkaz


I was writing some unit tests for our own wrapper around the Lucene regex 
classes, and got tripped up by something interesting.

The regex "cat." will match "cats" but also anything with "cat" and 1+ 
following letters (e.g. "cathy", "catcher", ...)  It is as if there is an 
implicit .* always added to the end of the regex.

Here's a unit test for the behaviour I would expect myself:

    @Test
    public void testNecessity() throws Exception {
        File dir = new File(new File(System.getProperty("java.io.tmpdir")), 
"index");
        IndexWriter writer = new IndexWriter(dir, new StandardAnalyzer(), true);
        try {
            Document doc = new Document();
            doc.add(new Field("field", "cat cats cathy", Field.Store.YES, 
Field.Index.TOKENIZED));
            writer.addDocument(doc);
        } finally {
            writer.close();
        }

        IndexReader reader = IndexReader.open(dir);
        try {
            TermEnum terms = new RegexQuery(new Term("field", 
"cat.")).getEnum(reader);
            assertEquals("Wrong term", "cats", terms.term());
            assertFalse("Should have only been one term", terms.next());
        } finally {
            reader.close();
        }
    }

This test fails on the term check with terms.term() equal to "cathy".

Our workaround is to mangle the query like this:

    String fixed = String.format("(?:%s)$", original);


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