Changed FindOperation to only use the $query meta-operator if there other meta-operators that are being used.

This is necessary to make the check for whether the server is fsync-locked work, as that particular usage of OP_QUERY
does not handle the $query meta-operator and simply closed the connection.

 JAVA-1886

Author: jyemin

driver-core/src/main/com/mongodb/operation/FindOperation.java

@@ -537,8 +537,8 @@ private int getNumberToReturn() {
     }
 
     private BsonDocument asDocument(final ConnectionDescription connectionDescription, final ReadPreference readPreference) {
-        BsonDocument document = modifiers != null ? modifiers : new BsonDocument();
-        document.put("$query", filter != null ? filter : new BsonDocument());
+        BsonDocument document = new BsonDocument();
+
         if (sort != null) {
             document.put("$orderby", sort);
         }
@@ -551,6 +551,16 @@ private BsonDocument asDocument(final ConnectionDescription connectionDescriptio
             document.put("$readPreference", readPreference.toDocument());
         }
 
+        if (modifiers != null) {
+            document.putAll(modifiers);
+        }
+
+        if (document.isEmpty()) {
+            document = filter != null ? filter : new BsonDocument();
+        } else {
+            document.put("$query", filter != null ? filter : new BsonDocument());
+        }
+
         return document;
     }
 

driver-core/src/test/functional/com/mongodb/operation/FindOperationSpecification.groovy

@@ -293,6 +293,33 @@ class FindOperationSpecification extends OperationFunctionalSpecification {
         count == 500
     }
 
+    def 'should call query on Connection with no $query when there are no other meta operators'() {
+        given:
+        def findOperation = new FindOperation<Document>(getNamespace(), new DocumentCodec())
+                .projection(new BsonDocument('x', new BsonInt32(1)))
+                .filter(new BsonDocument('z', new BsonString('val')))
+        def binding = Stub(ReadBinding)
+        def source = Stub(ConnectionSource)
+        def connection = Mock(Connection)
+        binding.readPreference >> ReadPreference.primary()
+        binding.readConnectionSource >> source
+        source.connection >> connection
+        source.retain() >> source
+
+        when:
+        findOperation.execute(binding)
+
+        then:
+        _ * connection.description >> new ConnectionDescription(new ConnectionId(new ServerId(new ClusterId(), new ServerAddress())),
+                                                                new ServerVersion(2, 6), ServerType.STANDALONE, 1000, 100000, 100000)
+
+        1 * connection.query(getNamespace(), findOperation.filter,
+                             findOperation.projection, 0, 0, false, false, false, false, false, false, _) >>
+        new QueryResult(getNamespace(), [new BsonDocument('n', new BsonInt32(1))], 0, new ServerAddress())
+
+        1 * connection.release()
+    }
+
     def 'should call query on Connection with correct arguments for an explain'() {
         given:
         def findOperation = new FindOperation<Document>(getNamespace(), new DocumentCodec())

driver/src/test/functional/com/mongodb/MongoMethodsTest.java

@@ -21,7 +21,9 @@
 import java.net.UnknownHostException;
 
 import static org.hamcrest.CoreMatchers.hasItems;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
 
 public class MongoMethodsTest extends DatabaseTestCase {
     @Test
@@ -37,4 +39,15 @@ public void shouldGetDatabaseNames() throws UnknownHostException {
             getClient().dropDatabase("test2");
         }
     }
+
+    @Test
+    public void shouldLockAndUnlock() {
+        assertFalse(getClient().isLocked());
+
+        getClient().fsyncAndLock();
+        assertTrue(getClient().isLocked());
+
+        getClient().unlock();
+        assertFalse(getClient().isLocked());
+    }
 }