LUCENE-825: make sure FileNotFoundException is returned if directory.list() returns null

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@515495 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -43,6 +43,11 @@ Bug fixes
     IndexWriter's mergeSegments, and also during
     IndexWriter.addIndexes.  (Mike McCandless)
 
+ 6. LUCENE-825: If directory is removed after
+    FSDirectory.getDirectory() but before IndexReader.open you now get
+    a FileNotFoundException like Lucene pre-2.1 (before this fix you
+    got an NPE).  (Mike McCandless)
+
 New features
 
  1. LUCENE-759: Added two n-gram-producing TokenFilters.

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

@@ -481,6 +481,10 @@ final class SegmentInfos extends Vector {
             files = fileDirectory.list();
           }
 
+          if (files == null) {
+            throw new FileNotFoundException("no segments* file found in directory " + directory + ": list() returned null");
+          }
+
           gen = getCurrentSegmentGeneration(files);
 
           if (gen == -1) {

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

@@ -974,6 +974,28 @@ public class TestIndexReader extends TestCase
       return s;
     }
 
+    public void testOpenReaderAfterDelete() throws IOException {
+      File dirFile = new File(System.getProperty("tempDir"),
+                          "deletetest");
+      Directory dir = FSDirectory.getDirectory(dirFile);
+      try {
+        IndexReader reader = IndexReader.open(dir);
+        fail("expected CorruptIndexException");
+      } catch (FileNotFoundException e) {
+        // expected
+      }
+
+      dirFile.delete();
+
+      // Make sure we still get a CorruptIndexException (not NPE):
+      try {
+        IndexReader reader = IndexReader.open(dir);
+        fail("expected CorruptIndexException");
+      } catch (FileNotFoundException e) {
+        // expected
+      }
+    }
+
     private void deleteReaderReaderConflict(boolean optimize) throws IOException
     {
         Directory dir = getDirectory();