Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 953441)
+++ lucene/CHANGES.txt	(working copy)
@@ -481,6 +481,10 @@
   files when a mergedSegmentWarmer is set on IndexWriter.  (Mike
   McCandless)
 
+* LUCENE-2496: Don't throw NPE if IndexWriter is opened with CREATE on
+  a prior (corrupt) index missing its segments_N file.  (Mike
+  McCandless)
+
 New features
 
 * LUCENE-2128: Parallelized fetching document frequencies during weight
Index: lucene/src/test/org/apache/lucene/index/TestIndexWriter.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexWriter.java	(revision 953441)
+++ lucene/src/test/org/apache/lucene/index/TestIndexWriter.java	(working copy)
@@ -4954,5 +4954,32 @@
     writer.close();
     assertEquals("expected a no-op close after IW.rollback()", 0, dir.listAll().length);
   }
-  
+
+  public void testNoSegmentFile() throws IOException {
+    File tempDir = _TestUtil.getTempDir("noSegmentFile");
+    try {
+      Directory dir = FSDirectory.open(tempDir);
+      dir.setLockFactory(new NoLockFactory());
+      IndexWriter w = new IndexWriter(dir, new IndexWriterConfig(
+                                                                 TEST_VERSION_CURRENT, new MockAnalyzer())
+                                      .setMaxBufferedDocs(2));
+
+      Document doc = new Document();
+      doc.add(new Field("c", "val", Store.YES, Index.ANALYZED, TermVector.WITH_POSITIONS_OFFSETS));
+      w.addDocument(doc);
+      w.addDocument(doc);
+      String[] files = dir.listAll();
+      for(String file : files) {
+        System.out.println("file=" + file);
+      }
+      IndexWriter w2 = new IndexWriter(dir, new IndexWriterConfig(
+                                                                  TEST_VERSION_CURRENT, new MockAnalyzer())
+                                       .setMaxBufferedDocs(2).setOpenMode(OpenMode.CREATE));
+
+      w2.close();
+      dir.close();
+    } finally {
+      _TestUtil.rmDir(tempDir);
+    }
+  }
 }
Index: lucene/src/java/org/apache/lucene/index/IndexFileDeleter.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/IndexFileDeleter.java	(revision 953441)
+++ lucene/src/java/org/apache/lucene/index/IndexFileDeleter.java	(working copy)
@@ -134,8 +134,10 @@
     this.docWriter = docWriter;
     this.infoStream = infoStream;
 
+    final String currentSegmentsFile = segmentInfos.getCurrentSegmentFileName();
+
     if (infoStream != null)
-      message("init: current segments file is \"" + segmentInfos.getCurrentSegmentFileName() + "\"; deletionPolicy=" + policy);
+      message("init: current segments file is \"" + currentSegmentsFile + "\"; deletionPolicy=" + policy);
 
     this.policy = policy;
     this.directory = directory;
@@ -146,7 +148,6 @@
     indexFilenameFilter = new IndexFileNameFilter(codecs);
     
     CommitPoint currentCommitPoint = null;
-    boolean seenIndexFiles = false;
     String[] files = null;
     try {
       files = directory.listAll();
@@ -158,7 +159,6 @@
     for (String fileName : files) {
 
       if ((indexFilenameFilter.accept(null, fileName)) && !fileName.endsWith("write.lock") && !fileName.equals(IndexFileNames.SEGMENTS_GEN)) {
-        seenIndexFiles = true;
         
         // Add this file to refCounts with initial count 0:
         getRefCount(fileName);
@@ -201,10 +201,7 @@
       }
     }
 
-    // If we haven't seen any Lucene files, then currentCommitPoint is expected
-    // to be null, because it means it's a fresh Directory. Therefore it cannot
-    // be any NFS cache issues - so just ignore.
-    if (currentCommitPoint == null && seenIndexFiles) {
+    if (currentCommitPoint == null && currentSegmentsFile != null) {
       // We did not in fact see the segments_N file
       // corresponding to the segmentInfos that was passed
       // in.  Yet, it must exist, because our caller holds
@@ -214,7 +211,7 @@
       // try now to explicitly open this commit point:
       SegmentInfos sis = new SegmentInfos();
       try {
-        sis.read(directory, segmentInfos.getCurrentSegmentFileName(), codecs);
+        sis.read(directory, currentSegmentsFile, codecs);
       } catch (IOException e) {
         throw new CorruptIndexException("failed to locate current segments_N file");
       }
@@ -244,7 +241,7 @@
 
     // Finally, give policy a chance to remove things on
     // startup:
-    if (seenIndexFiles) {
+    if (currentSegmentsFile != null) {
       policy.onInit(commits);
     }