Fix notNull checks and add unit tests for listDatabaseNames and listCollectionNames

Author: jyemin

driver/src/main/com/mongodb/MappingIterable.java

@@ -31,6 +31,10 @@ class MappingIterable<U, V> implements MongoIterable<V> {
         this.mapper = mapper;
     }
 
+    MongoIterable<U> getMapped() {
+        return iterable;
+    }
+
     @Override
     public MongoCursor<V> iterator() {
         return new MongoMappingCursor<U, V>(iterable.iterator(), mapper);

driver/src/main/com/mongodb/MongoClient.java

@@ -382,11 +382,11 @@ public MongoIterable<String> listDatabaseNames() {
      * @mongodb.driver.manual reference/command/listDatabases List Databases
      */
     public MongoIterable<String> listDatabaseNames(final ClientSession clientSession) {
+        notNull("clientSession", clientSession);
         return executeListDatabaseNames(clientSession);
     }
 
     private MongoIterable<String> executeListDatabaseNames(final ClientSession clientSession) {
-        notNull("clientSession", clientSession);
         return executeListDatabases(clientSession, BsonDocument.class).map(new Function<BsonDocument, String>() {
             @Override
             public String apply(final BsonDocument result) {

driver/src/main/com/mongodb/MongoDatabaseImpl.java

@@ -170,6 +170,7 @@ public void drop() {
 
     @Override
     public void drop(final ClientSession clientSession) {
+        notNull("clientSession", clientSession);
         executeDrop(clientSession);
     }
 
@@ -184,11 +185,11 @@ public MongoIterable<String> listCollectionNames() {
 
     @Override
     public MongoIterable<String> listCollectionNames(final ClientSession clientSession) {
+        notNull("clientSession", clientSession);
         return executeListCollectionNames(clientSession);
     }
 
     private MongoIterable<String> executeListCollectionNames(final ClientSession clientSession) {
-        notNull("clientSession", clientSession);
         return executeListCollections(clientSession, BsonDocument.class)
                        .map(new Function<BsonDocument, String>() {
                            @Override
@@ -296,12 +297,12 @@ public void createView(final ClientSession clientSession, final String viewName,
     @Override
     public void createView(final ClientSession clientSession, final String viewName, final String viewOn,
                            final List<? extends Bson> pipeline, final CreateViewOptions createViewOptions) {
+        notNull("clientSession", clientSession);
         executeCreateView(clientSession, viewName, viewOn, pipeline, createViewOptions);
     }
 
     private void executeCreateView(final ClientSession clientSession, final String viewName, final String viewOn,
                                    final List<? extends Bson> pipeline, final CreateViewOptions createViewOptions) {
-        notNull("clientSession", clientSession);
         notNull("createViewOptions", createViewOptions);
         executor.execute(new CreateViewOperation(name, viewName, viewOn, createBsonDocumentList(pipeline), writeConcern)
                                  .collation(createViewOptions.getCollation()),

driver/src/test/unit/com/mongodb/MongoClientSpecification.groovy

@@ -44,11 +44,12 @@ class MongoClientSpecification extends Specification {
         given:
         def executor = new TestOperationExecutor([null, null])
         def client = Spy(MongoClient) {
-            2 * createOperationExecutor() >> {
+            3 * createOperationExecutor() >> {
                 executor
             }
         }
         def listDatabasesMethod = client.&listDatabases
+        def listDatabasesNamesMethod = client.&listDatabaseNames
 
         when:
         def listDatabasesIterable = execute(listDatabasesMethod, session)
@@ -64,6 +65,14 @@ class MongoClientSpecification extends Specification {
         expect listDatabasesIterable, isTheSameAs(new ListDatabasesIterableImpl<BsonDocument>(session, BsonDocument,
                 getDefaultCodecRegistry(), primary(), executor))
 
+        when:
+        def listDatabaseNamesIterable = execute(listDatabasesNamesMethod, session)
+
+        then:
+        // listDatabaseNamesIterable is an instance of a MappingIterable, so have to get the mapped iterable inside it
+        expect listDatabaseNamesIterable.getMapped(), isTheSameAs(new ListDatabasesIterableImpl<BsonDocument>(session, BsonDocument,
+                getDefaultCodecRegistry(), primary(), executor))
+
         cleanup:
         client?.close()
 

driver/src/test/unit/com/mongodb/MongoDatabaseSpecification.groovy

@@ -208,6 +208,7 @@ class MongoDatabaseSpecification extends Specification {
         def executor = new TestOperationExecutor([null, null, null])
         def database = new MongoDatabaseImpl(name, codecRegistry, readPreference, writeConcern, readConcern, executor)
         def listCollectionsMethod = database.&listCollections
+        def listCollectionNamesMethod = database.&listCollectionNames
 
         when:
         def listCollectionIterable = execute(listCollectionsMethod, session)
@@ -223,6 +224,14 @@ class MongoDatabaseSpecification extends Specification {
         expect listCollectionIterable, isTheSameAs(new ListCollectionsIterableImpl<BsonDocument>(session, name, BsonDocument, codecRegistry,
                 primary(), executor))
 
+        when:
+        def listCollectionNamesIterable = execute(listCollectionNamesMethod, session)
+
+        then:
+        // listCollectionNamesIterable is an instance of a MappingIterable, so have to get the mapped iterable inside it
+        expect listCollectionNamesIterable.getMapped(), isTheSameAs(new ListCollectionsIterableImpl<BsonDocument>(session, name,
+                BsonDocument, codecRegistry, primary(), executor))
+
         where:
         session << [null, Stub(ClientSession)]
     }