DATAMONGO-1133 - Assert that field aliasing is honored in aggregation operations.

Added some test to show that field aliases are honored during object rendering in aggregation operations.

Original pull request: #279.

Author: Thomas Darimont

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/AggregationTests.java

@@ -125,6 +125,7 @@ private void cleanDb() {
 		mongoTemplate.dropCollection(Person.class);
 		mongoTemplate.dropCollection(Reservation.class);
 		mongoTemplate.dropCollection(Venue.class);
+		mongoTemplate.dropCollection(MeterData.class);
 	}
 
 	/**
@@ -1044,6 +1045,30 @@ public void shouldSupportGeoNearQueriesForAggregationWithDistanceField() {
 		assertThat((Double) firstResult.get("distance"), closeTo(117.620092203928, 0.00001));
 	}
 
+	/**
+	 * @see DATAMONGO-1133
+	 */
+	@Test
+	public void shouldHonorFieldAliasesForFieldReferences() {
+
+		mongoTemplate.insert(new MeterData("m1", "counter1", 42));
+		mongoTemplate.insert(new MeterData("m1", "counter1", 13));
+		mongoTemplate.insert(new MeterData("m1", "counter1", 45));
+
+		TypedAggregation<MeterData> agg = newAggregation(MeterData.class, //
+				match(where("resourceId").is("m1")), //
+				group("counterName").sum("counterVolume").as("totalValue") //
+		);
+
+		AggregationResults<DBObject> results = mongoTemplate.aggregate(agg, DBObject.class);
+
+		assertThat(results.getMappedResults(), hasSize(1));
+		DBObject result = results.getMappedResults().get(0);
+
+		assertThat(result.get("_id"), is(equalTo((Object) "counter1")));
+		assertThat(result.get("totalValue"), is(equalTo((Object) 42.0)));
+	}
+
 	private void assertLikeStats(LikeStats like, String id, long count) {
 
 		assertThat(like, is(notNullValue()));

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/MeterData.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * 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 org.springframework.data.mongodb.core.aggregation;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.Field;
+
+/**
+ * @author Thomas Darimont
+ */
+public class MeterData {
+
+	@Id String resourceId;
+	@Field("counter_name") String counterName;
+	double counterVolume;
+
+	public MeterData() {}
+
+	public MeterData(String resourceId, String counterName, double counterVolume) {
+
+		this.resourceId = resourceId;
+		this.counterName = counterName;
+		this.counterVolume = counterVolume;
+	}
+}

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/TypeBasedAggregationOperationContextUnitTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2014 the original author or authors.
+ * Copyright 2013-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -169,6 +169,24 @@ public void rendersAggregationOptionsInTypedAggregationContextCorrectly() {
 		assertThat(dbo.get("cursor"), is((Object) new BasicDBObject("foo", 1)));
 	}
 
+	/**
+	 * @see DATAMONGO-1133
+	 */
+	@Test
+	public void shouldHonorAliasedFieldsInGroupExpressions() {
+
+		TypeBasedAggregationOperationContext context = getContext(MeterData.class);
+		TypedAggregation<MeterData> agg = newAggregation(MeterData.class,
+				group("counterName").sum("counterVolume").as("totalCounterVolume"));
+
+		DBObject dbo = agg.toDbObject("meterData", context);
+		DBObject group = getPipelineElementFromAggregationAt(dbo, 0);
+
+		DBObject definition = (DBObject) group.get("$group");
+
+		assertThat(definition.get("_id"), is(equalTo((Object) "$counter_name")));
+	}
+
 	@Document(collection = "person")
 	public static class FooPerson {