LUCENE-1179: allow Fields with empty string field names

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@628080 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -73,6 +73,10 @@ Bug fixes
     without checking if the scorer is already at the right position.
     scorer.skipTo(scorer.doc()) is not a NOOP, it behaves as 
     scorer.next(). (Eks Dev, Michael Busch)
+
+ 5. LUCENE-1179: Fixed assert statement that was incorrectly
+    preventing Fields with empty-string field name from working.
+    (Sergey Kabashnyuk via Mike McCandless)
 	
 New features
 

src/java/org/apache/lucene/index/TermInfosWriter.java

@@ -111,8 +111,15 @@ final class TermInfosWriter {
   private int compareToLastTerm(int fieldNumber, char[] termText, int start, int length) {
     int pos = 0;
 
-    if (lastFieldNumber != fieldNumber)
+    if (lastFieldNumber != fieldNumber) {
-      return fieldInfos.fieldName(lastFieldNumber).compareTo(fieldInfos.fieldName(fieldNumber));
+      final int cmp = fieldInfos.fieldName(lastFieldNumber).compareTo(fieldInfos.fieldName(fieldNumber));
+      // If there is a field named "" (empty string) then we
+      // will get 0 on this comparison, yet, it's "OK".  But
+      // it's not OK if two different field numbers map to
+      // the same name.
+      if (cmp != 0 || lastFieldNumber != -1)
+        return cmp;
+    }
 
     while(pos < length && pos < lastTermTextLength) {
       final char c1 = lastTermText[pos];

src/test/org/apache/lucene/index/TestIndexWriter.java

@@ -3113,4 +3113,14 @@ public class TestIndexWriter extends LuceneTestCase
     ir.close();
     dir.close();
   }
+
+  // LUCENE-1179
+  public void testEmptyFieldName() throws IOException {
+    MockRAMDirectory dir = new MockRAMDirectory();
+    IndexWriter writer = new IndexWriter(dir, new WhitespaceAnalyzer());
+    Document doc = new Document();
+    doc.add(new Field("", "a b c", Field.Store.NO, Field.Index.TOKENIZED));
+    writer.addDocument(doc);
+    writer.close();
+  }
 }