DATAMONGO-1893 - Polishing.

Inherit fields from previous operation if at least one field is excluded. Extend FieldsExposingAggregationOperation to conditionally inherit fields.

Original pull request: #538.

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

@@ -59,7 +59,7 @@ class AggregationOperationRenderer {
 				FieldsExposingAggregationOperation exposedFieldsOperation = (FieldsExposingAggregationOperation) operation;
 				ExposedFields fields = exposedFieldsOperation.getFields();
 
-				if (operation instanceof InheritsFieldsAggregationOperation) {
+				if (operation instanceof InheritsFieldsAggregationOperation || exposedFieldsOperation.inheritsFields()) {
 					contextToUse = new InheritingExposedFieldsAggregationOperationContext(fields, contextToUse);
 				} else {
 					contextToUse = fields.exposesNoFields() ? DEFAULT_CONTEXT

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

@@ -33,9 +33,26 @@ public interface FieldsExposingAggregationOperation extends AggregationOperation
 	 */
 	ExposedFields getFields();
 
+	/**
+	 * @return {@literal true} to conditionally inherit fields from previous operations.
+	 * @since 2.0.6
+	 */
+	default boolean inheritsFields() {
+		return false;
+	}
+
 	/**
 	 * Marker interface for {@link AggregationOperation} that inherits fields from previous operations.
 	 */
-	interface InheritsFieldsAggregationOperation extends FieldsExposingAggregationOperation {}
+	interface InheritsFieldsAggregationOperation extends FieldsExposingAggregationOperation {
 
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#inheritsFields()
+		 */
+		@Override
+		default boolean inheritsFields() {
+			return true;
+		}
+	}
 }

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

@@ -183,6 +183,18 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		return fields != null ? fields : ExposedFields.empty();
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#inheritsFields()
+	 */
+	@Override
+	public boolean inheritsFields() {
+
+		return projections.stream().filter(FieldProjection.class::isInstance) //
+				.map(FieldProjection.class::cast) //
+				.anyMatch(FieldProjection::isExcluded);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
@@ -1339,6 +1351,13 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 				return projections;
 			}
 
+			/**
+			 * @return {@literal true} if this field is excluded.
+			 */
+			public boolean isExcluded() {
+				return Boolean.FALSE.equals(value);
+			}
+
 			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.Projection#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)

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

@@ -204,9 +204,19 @@ public class ProjectionOperationUnitTests {
 		ProjectionOperation projectionOp = new ProjectionOperation().andExclude("foo");
 		Document document = projectionOp.toDocument(Aggregation.DEFAULT_CONTEXT);
 		Document projectClause = DocumentTestUtils.getAsDocument(document, PROJECT);
+
+		assertThat(projectionOp.inheritsFields()).isTrue();
 		assertThat((Integer) projectClause.get("foo")).isEqualTo(0);
 	}
 
+	@Test // DATAMONGO-1893
+	public void includeShouldNotInheritFields() {
+
+		ProjectionOperation projectionOp = new ProjectionOperation().andInclude("foo");
+
+		assertThat(projectionOp.inheritsFields()).isFalse();
+	}
+
 	@Test // DATAMONGO-758
 	public void excludeShouldAllowExclusionOfUnderscoreId() {
 

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

@@ -22,6 +22,8 @@ import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;
 import static org.springframework.data.mongodb.core.aggregation.Fields.*;
 import static org.springframework.data.mongodb.test.util.IsBsonObject.*;
 
+import lombok.AllArgsConstructor;
+
 import java.util.Arrays;
 import java.util.List;
 
@@ -35,8 +37,8 @@ import org.mockito.junit.MockitoJUnitRunner;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.convert.support.GenericConversionService;
 import org.springframework.data.annotation.Id;
-import org.springframework.data.annotation.PersistenceConstructor;
 import org.springframework.data.convert.CustomConversions;
+import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.Sort.Direction;
 import org.springframework.data.mapping.MappingException;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
@@ -188,6 +190,19 @@ public class TypeBasedAggregationOperationContextUnitTests {
 				.containing("age", "$age.value"));
 	}
 
+	@Test // DATAMONGO-1893
+	public void considersIncludedFieldsFromSingleExclusionsCorrectly() {
+
+		AggregationOperationContext context = getContext(FooPerson.class);
+		TypedAggregation<FooPerson> agg = newAggregation(FooPerson.class, project() //
+				.andExclude("name"), sort(Sort.by("age.value", "lastName")));
+
+		Document dbo = agg.toDocument("person", context);
+
+		Document sort = getPipelineElementFromAggregationAt(dbo, 1);
+		assertThat(getAsDocument(sort, "$sort"), is(equalTo(new Document("age.value", 1).append("last_name", 1))));
+	}
+
 	@Test // DATAMONGO-1133
 	public void shouldHonorAliasedFieldsInGroupExpressions() {
 
@@ -344,18 +359,13 @@ public class TypeBasedAggregationOperationContextUnitTests {
 	}
 
 	@org.springframework.data.mongodb.core.mapping.Document(collection = "person")
+	@AllArgsConstructor
 	public static class FooPerson {
 
 		final ObjectId id;
 		final String name;
+		@org.springframework.data.mongodb.core.mapping.Field("last_name") final String lastName;
 		final Age age;
-
-		@PersistenceConstructor
-		FooPerson(ObjectId id, String name, Age age) {
-			this.id = id;
-			this.name = name;
-			this.age = age;
-		}
 	}
 
 	public static class Age {