AggregationOperation::toDocument method is deprecated, but MongoTemplate still uses it

[MVardumyan]

I need to use custom AggregationOperation for $group operation in my aggregation query. So I've created class like this:

public class CustomGroupingOperation implements AggregationOperation {
    @Override
    public Document toDocument(AggregationOperationContext context) {
        return null;
    }

    @Override
    public List<Document> toPipelineStages(AggregationOperationContext context) {
        return List.of(new Document("$group",
                new Document("_id", new Document("name", new Document("$ifNull", new Object[] {"$name", null})))
                        .append("records", new Document("$push", "$$ROOT"))));
    }

    @Override
    public String getOperator() {
        return AggregationOperation.super.getOperator();
    }
}

According to documentation, toDocument method is deprecated in favor of toPipelineStages method. However, when I use this class with mongoTemplate like this:

AggregationOperation grouping = new CustomGroupingOperation();

TypedAggregation<MyPojoClass> aggregation = newAggregation(
        Object.class,
        match
        grouping
);
return mongoTemplate.aggregate(aggregation, MyPojoClass.class).getMappedResults();

During debugging I see that application enters toDocument method instead of toPipelineStages.
Should I change something in my approach, or is this a bug?

UPD Here are my drivers from spring-boot-starter-data-mongodb-2.7.2.pom:

    <dependency>
      <groupId>org.mongodb</groupId>
      <artifactId>mongodb-driver-sync</artifactId>
      <version>4.6.1</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.data</groupId>
      <artifactId>spring-data-mongodb</artifactId>
      <version>3.4.2</version>
      <scope>compile</scope>
    </dependency>

[christophstrobl]

Good catch - thanks for reporting. The AggregationPipeline is still using it to look up $out stages. We'll take care of this.