Avoid multiple mapping iterations.

A 2nd pass is no longer needed as the context already does all the work.

Closes: #4043
Original pull request: #4240

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/AggregationUtil.java

@@ -32,7 +32,6 @@ import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.util.Lazy;
 import org.springframework.lang.Nullable;
-import org.springframework.util.ObjectUtils;
 
 /**
  * Utility methods to map {@link org.springframework.data.mongodb.core.aggregation.Aggregation} pipeline definitions and
@@ -96,12 +95,7 @@ class AggregationUtil {
 	 * @return
 	 */
 	List<Document> createPipeline(Aggregation aggregation, AggregationOperationContext context) {
-
-		if (ObjectUtils.nullSafeEquals(context, Aggregation.DEFAULT_CONTEXT)) {
-			return aggregation.toPipeline(context);
-		}
-
-		return mapAggregationPipeline(aggregation.toPipeline(context));
+		return aggregation.toPipeline(context);
 	}
 
 	/**
@@ -112,16 +106,7 @@ class AggregationUtil {
 	 * @return
 	 */
 	Document createCommand(String collection, Aggregation aggregation, AggregationOperationContext context) {
-
-		Document command = aggregation.toDocument(collection, context);
-
-		if (!ObjectUtils.nullSafeEquals(context, Aggregation.DEFAULT_CONTEXT)) {
-			return command;
-		}
-
-		command.put("pipeline", mapAggregationPipeline(command.get("pipeline", List.class)));
-
-		return command;
+		return aggregation.toDocument(collection, context);
 	}
 
 	private List<Document> mapAggregationPipeline(List<Document> pipeline) {

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

@@ -43,11 +43,11 @@ import java.util.stream.Stream;
 
 import org.assertj.core.data.Offset;
 import org.bson.Document;
+import org.bson.types.ObjectId;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
-
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.data.annotation.Id;
 import org.springframework.data.domain.Sort;
@@ -65,6 +65,7 @@ import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.E
 import org.springframework.data.mongodb.core.geo.GeoJsonPoint;
 import org.springframework.data.mongodb.core.index.GeoSpatialIndexType;
 import org.springframework.data.mongodb.core.index.GeospatialIndex;
+import org.springframework.data.mongodb.core.mapping.MongoId;
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
@@ -1933,6 +1934,24 @@ public class AggregationTests {
 		assertThat(results.getMappedResults()).hasSize(1);
 	}
 
+	@Test // GH-4043
+	void considersMongoIdWithinTypedCollections() {
+
+		UserRef userRef = new UserRef();
+		userRef.id = "4ee921aca44fd11b3254e001";
+		userRef.name = "u-1";
+
+		Widget widget = new Widget();
+		widget.id = "w-1";
+		widget.users = List.of(userRef);
+
+		mongoTemplate.save(widget);
+
+		Criteria criteria = Criteria.where("users").elemMatch(Criteria.where("id").is("4ee921aca44fd11b3254e001"));
+		AggregationResults<Widget> aggregate = mongoTemplate.aggregate(newAggregation(match(criteria)), Widget.class, Widget.class);
+		assertThat(aggregate.getMappedResults()).contains(widget);
+	}
+
 	private void createUsersWithReferencedPersons() {
 
 		mongoTemplate.dropCollection(User.class);
@@ -2250,4 +2269,18 @@ public class AggregationTests {
 		@Id String id;
 		MyEnum enumValue;
 	}
+
+	@lombok.Data
+	static class Widget {
+		@Id
+		String id;
+		List<UserRef> users;
+	}
+
+	@lombok.Data
+	static class UserRef {
+		@MongoId
+		String id;
+		String name;
+	}
 }