Additional test

Author: christophstrobl

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

@@ -19,16 +19,21 @@
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.springframework.data.domain.Sort.Direction.DESC;
+import static org.springframework.data.mongodb.core.aggregation.Aggregation.newAggregation;
 import static org.springframework.data.mongodb.core.aggregation.Aggregation.project;
 import static org.springframework.data.mongodb.core.aggregation.Aggregation.sort;
 
 import java.time.ZonedDateTime;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Stream;
 
 import org.assertj.core.api.Assertions;
 import org.bson.Document;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 import org.springframework.data.annotation.Id;
 import org.springframework.data.convert.ConverterBuilder;
 import org.springframework.data.convert.CustomConversions;
@@ -37,6 +42,7 @@
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
 import org.springframework.data.mongodb.core.convert.NoOpDbRefResolver;
 import org.springframework.data.mongodb.core.convert.QueryMapper;
+import org.springframework.data.mongodb.core.mapping.Field;
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.test.util.MongoTestMappingContext;
 
@@ -100,6 +106,37 @@ void appliesConversionToValuesUsedInAggregation() {
 				.isInstanceOf(String.class);
 	}
 
+	@ParameterizedTest // GH-4722
+	@MethodSource("studentAggregationContexts")
+	void mapsOperationThatDoesNotExposeDedicatedFieldsCorrectly(AggregationOperationContext aggregationContext) {
+
+		var agg = newAggregation(Student.class, Aggregation.unwind("grades"), Aggregation.replaceRoot("grades"),
+				Aggregation.project("grades"));
+
+		List<Document> mappedPipeline = AggregationOperationRenderer.toDocument(agg.getPipeline().getOperations(),
+				aggregationContext);
+
+		Assertions.assertThat(mappedPipeline).last().isEqualTo(Document.parse("{\"$project\": {\"grades\": 1}}"));
+	}
+
+	private static Stream<Arguments> studentAggregationContexts() {
+
+		MongoTestMappingContext ctx = new MongoTestMappingContext(cfg -> {
+			cfg.initialEntitySet(Student.class);
+		});
+
+		MappingMongoConverter mongoConverter = new MappingMongoConverter(NoOpDbRefResolver.INSTANCE, ctx);
+		mongoConverter.afterPropertiesSet();
+
+		QueryMapper queryMapper = new QueryMapper(mongoConverter);
+
+		return Stream.of(
+				Arguments
+						.of(new TypeBasedAggregationOperationContext(Student.class, ctx, queryMapper, FieldLookupPolicy.strict())),
+				Arguments.of(
+						new TypeBasedAggregationOperationContext(Student.class, ctx, queryMapper, FieldLookupPolicy.relaxed())));
+	}
+
 	record TestRecord(@Id String field1, String field2, LayerOne layerOne) {
 		record LayerOne(List<LayerTwo> layerTwo) {
 		}
@@ -110,4 +147,17 @@ record LayerTwo(LayerThree layerThree) {
 		record LayerThree(int fieldA, int fieldB) {
 		}
 	}
+
+	static class Student {
+
+		@Field("mark") List<Grade> grades;
+
+	}
+
+	static class Grade {
+
+		int points;
+		String grades;
+	}
+
 }