LUCENE-7410: Make TestReaderClosed pass if the IndexSearcher wraps a threadpool.

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

@@ -79,7 +79,9 @@ public class TestReaderClosed extends LuceneTestCase {
     assertTrue(reader.getRefCount() > 0);
     LeafReader wrappedReader = new ParallelLeafReader(getOnlyLeafReader(reader));
 
-    IndexSearcher searcher = newSearcher(wrappedReader);
+    // We wrap with a OwnCacheKeyMultiReader so that closing the underlying reader
+    // does not terminate the threadpool (if that index searcher uses one)
+    IndexSearcher searcher = newSearcher(new OwnCacheKeyMultiReader(wrappedReader));
 
     TermRangeQuery query = TermRangeQuery.newStringRange("field", "a", "z", true, true);
     searcher.search(query, 5);
@@ -93,7 +95,9 @@ public class TestReaderClosed extends LuceneTestCase {
           ace = (AlreadyClosedException) t;
         }
       }
-      assertNotNull("Query failed, but not due to an AlreadyClosedException", ace);
+      if (ace == null) {
+        throw new AssertionError("Query failed, but not due to an AlreadyClosedException", e);
+      }
       assertEquals(
         "this IndexReader cannot be used anymore as one of its child readers was closed",
         ace.getMessage()

lucene/test-framework/src/java/org/apache/lucene/index/OwnCacheKeyMultiReader.java

@@ -0,0 +1,76 @@
+/*
+ * 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.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+import org.apache.lucene.util.IOUtils;
+
+/**
+ * A {@link MultiReader} that has its own cache key, occasionally useful for
+ * testing purposes.
+ */
+public final class OwnCacheKeyMultiReader extends MultiReader {
+
+  private final Set<ClosedListener> readerClosedListeners = new CopyOnWriteArraySet<>();
+
+  private final CacheHelper cacheHelper = new CacheHelper() {
+    private final CacheKey cacheKey = new CacheKey();
+
+    @Override
+    public CacheKey getKey() {
+      return cacheKey;
+    }
+
+    @Override
+    public void addClosedListener(ClosedListener listener) {
+        readerClosedListeners.add(listener);
+    }
+
+  };
+
+  /** Sole constructor. */
+  public OwnCacheKeyMultiReader(IndexReader... subReaders) throws IOException {
+    super(subReaders);
+  }
+
+  @Override
+  public CacheHelper getReaderCacheHelper() {
+    return cacheHelper;
+  }
+
+  @Override
+  void notifyReaderClosedListeners(Throwable th) throws IOException {
+    synchronized(readerClosedListeners) {
+      for(ClosedListener listener : readerClosedListeners) {
+        try {
+          listener.onClose(cacheHelper.getKey());
+        } catch (Throwable t) {
+          if (th == null) {
+            th = t;
+          } else {
+            th.addSuppressed(t);
+          }
+        }
+      }
+      IOUtils.reThrow(th);
+    }
+  }
+
+}