Ensure MappingIterables delegate to wrapped iterable

JAVA-2894

Author: rozza

driver-async/src/main/com/mongodb/async/client/MappingIterable.java

@@ -18,8 +18,8 @@
 
 import com.mongodb.Block;
 import com.mongodb.Function;
-import com.mongodb.async.SingleResultCallback;
 import com.mongodb.async.AsyncBatchCursor;
+import com.mongodb.async.SingleResultCallback;
 
 import java.util.Collection;
 
@@ -34,10 +34,6 @@ class MappingIterable<U, V> implements MongoIterable<V> {
         this.mapper = notNull("mapper", mapper);
     }
 
-    MongoIterable<U> getMapped() {
-        return iterable;
-    }
-
     @Override
     public void first(final SingleResultCallback<V> callback) {
         notNull("callback", callback);
@@ -46,6 +42,8 @@ public void first(final SingleResultCallback<V> callback) {
             public void onResult(final U result, final Throwable t) {
                 if (t != null) {
                     callback.onResult(null, t);
+                } else if (result == null) {
+                    callback.onResult(null, null);
                 } else {
                     callback.onResult(mapper.apply(result), null);
                 }
@@ -125,4 +123,8 @@ public void onResult(final AsyncBatchCursor<U> batchCursor, final Throwable t) {
             }
         });
     }
+
+    MongoIterable<U> getMapped() {
+        return iterable;
+    }
 }

driver-async/src/test/unit/com/mongodb/async/client/MappingIterableSpecification.groovy

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed 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 com.mongodb.async.client
+
+import com.mongodb.Block
+import com.mongodb.Function
+import com.mongodb.async.SingleResultCallback
+import spock.lang.Specification
+
+import static com.mongodb.CustomMatchers.isTheSameAs
+import static spock.util.matcher.HamcrestSupport.expect
+
+class MappingIterableSpecification extends Specification {
+
+    def 'should follow the MongoIterable interface as expected'() {
+        given:
+        def callback = Stub(SingleResultCallback)
+        def iterable = Mock(MongoIterable)
+        def mapper = { doc -> doc }
+        def mappingIterable = new MappingIterable(iterable, mapper)
+
+        when:
+        mappingIterable.first(callback)
+
+        then:
+        1 * iterable.first(_)
+
+        when:
+        mappingIterable.forEach( { } as Block, callback)
+
+        then:
+        1 * iterable.forEach(_, _)
+
+        when:
+        mappingIterable.into([], callback)
+
+        then:
+        1 * iterable.forEach(_, _)  // Use foreach to populate the target
+
+        when:
+        mappingIterable.batchSize(5)
+
+        then:
+        1 * iterable.batchSize(5)
+
+        when:
+        mappingIterable.getBatchSize()
+
+        then:
+        1 * iterable.getBatchSize() >> 5
+
+        when:
+        mappingIterable.batchCursor(callback)
+
+        then:
+        1 * iterable.batchCursor(_)
+
+        when:
+        def newMapper = { } as Function
+
+        then:
+        expect mappingIterable.map(newMapper), isTheSameAs(new MappingIterable(mappingIterable, newMapper))
+    }
+
+}

driver-sync/src/main/com/mongodb/client/internal/MappingIterable.java

@@ -34,10 +34,6 @@ 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);
@@ -46,11 +42,11 @@ public MongoCursor<V> iterator() {
     @Nullable
     @Override
     public V first() {
-        MongoCursor<V> iterator = iterator();
-        if (!iterator.hasNext()) {
+        U first = iterable.first();
+        if (first == null) {
             return null;
         }
-        return iterator.next();
+        return mapper.apply(first);
     }
 
     @Override
@@ -84,4 +80,8 @@ public MappingIterable<U, V> batchSize(final int batchSize) {
     public <W> MongoIterable<W> map(final Function<V, W> newMap) {
         return new MappingIterable<V, W>(this, newMap);
     }
+
+    MongoIterable<U> getMapped() {
+        return iterable;
+    }
 }

driver-sync/src/test/unit/com/mongodb/client/internal/MappingIterableSpecification.groovy

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed 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 com.mongodb.client.internal
+
+import com.mongodb.Block
+import com.mongodb.Function
+import com.mongodb.client.MongoCursor
+import com.mongodb.client.MongoIterable
+import spock.lang.Specification
+
+import static com.mongodb.CustomMatchers.isTheSameAs
+import static spock.util.matcher.HamcrestSupport.expect
+
+class MappingIterableSpecification extends Specification {
+
+    def 'should follow the MongoIterable interface as expected'() {
+        given:
+        def iterable = Mock(MongoIterable)
+        def mapper = { doc -> doc }
+        def mappingIterable = new MappingIterable(iterable, mapper)
+
+        when:
+        mappingIterable.first()
+
+        then:
+        1 * iterable.first()
+
+        when:
+        mappingIterable.forEach( { } as Block)
+
+        then:
+        1 * iterable.forEach(_)
+
+        when:
+        mappingIterable.into([])
+
+        then:
+        1 * iterable.forEach(_)  // Use foreach to populate the target
+
+        when:
+        mappingIterable.batchSize(5)
+
+        then:
+        1 * iterable.batchSize(5)
+
+        when:
+        mappingIterable.iterator()
+
+        then:
+        1 * iterable.iterator() >> Stub(MongoCursor)
+
+        when:
+        def newMapper = { } as Function
+
+        then:
+        expect mappingIterable.map(newMapper), isTheSameAs(new MappingIterable(mappingIterable, newMapper))
+    }
+
+}