Fix StoredFieldsConsumer finish (#13927)

lucene/CHANGES.txt

@@ -61,6 +61,7 @@ Bug Fixes
   when they were not sorted by startOffset. (Seunghan Jung)
 * GITHUB#13884: Remove broken .toArray from Long/CharObjectHashMap entirely. (Pan Guixin)
 * GITHUB#12686: Added support for highlighting IndexOrDocValuesQuery. (Prudhvi Godithi)
+* GITHUB#13927: Fix StoredFieldsConsumer finish. (linfn)
 
 Build
 ---------------------

lucene/core/src/java/org/apache/lucene/index/StoredFieldsConsumer.java

@@ -93,9 +93,8 @@ void finishDocument() throws IOException {
 
   void finish(int maxDoc) throws IOException {
     while (lastDoc < maxDoc - 1) {
-      startDocument(lastDoc);
+      startDocument(lastDoc + 1);
       finishDocument();
-      ++lastDoc;
     }
   }
 

lucene/core/src/test/org/apache/lucene/index/TestStoredFieldsConsumer.java

@@ -0,0 +1,84 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.index;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.FlushInfo;
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.tests.util.LuceneTestCase;
+import org.apache.lucene.util.StringHelper;
+import org.apache.lucene.util.Version;
+
+public class TestStoredFieldsConsumer extends LuceneTestCase {
+
+  public void testFinish() throws IOException {
+    Directory dir = newDirectory();
+    IndexWriterConfig iwc = new IndexWriterConfig();
+    SegmentInfo si =
+        new SegmentInfo(
+            dir,
+            Version.LATEST,
+            null,
+            "_0",
+            -1,
+            false,
+            false,
+            iwc.getCodec(),
+            Collections.emptyMap(),
+            StringHelper.randomId(),
+            new HashMap<>(),
+            null);
+
+    AtomicInteger startDocCounter = new AtomicInteger(), finishDocCounter = new AtomicInteger();
+    StoredFieldsConsumer consumer =
+        new StoredFieldsConsumer(iwc.getCodec(), dir, si) {
+          @Override
+          void startDocument(int docID) throws IOException {
+            super.startDocument(docID);
+            startDocCounter.incrementAndGet();
+          }
+
+          @Override
+          void finishDocument() throws IOException {
+            super.finishDocument();
+            finishDocCounter.incrementAndGet();
+          }
+        };
+
+    int numDocs = 3;
+    consumer.finish(numDocs);
+
+    si.setMaxDoc(numDocs);
+    SegmentWriteState state =
+        new SegmentWriteState(
+            null,
+            dir,
+            si,
+            new FieldInfos(new FieldInfo[0]),
+            null,
+            new IOContext(new FlushInfo(numDocs, 10)));
+    consumer.flush(state, null);
+    dir.close();
+
+    assertEquals(numDocs, startDocCounter.get());
+    assertEquals(numDocs, finishDocCounter.get());
+  }
+}