Add support for sorting simple arrays by direction.

Add method to provide sorting direction to sort array aggregation.

Related to: #4929
Original Pull Request: #4935

Signed-off-by: Nathan McDonald <nathan.mcdonald@uk.ey.com>

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

@@ -24,6 +24,7 @@ import java.util.List;
 import org.bson.Document;
 import org.springframework.data.domain.Range;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Sort.Direction;
 import org.springframework.data.mongodb.core.aggregation.ArrayOperators.Filter.AsBuilder;
 import org.springframework.data.mongodb.core.aggregation.ArrayOperators.Reduce.PropertyExpression;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
@@ -336,6 +337,22 @@ public class ArrayOperators {
 			return (usesExpression() ? SortArray.sortArrayOf(expression) : SortArray.sortArray(values)).by(sort);
 		}
 
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated array and sorts it by the given {@link Sort
+		 * order}.
+		 *
+		 * @return new instance of {@link SortArray}.
+		 * @since 4.0
+		 */
+		public SortArray sort(Direction direction) {
+
+			if (usesFieldRef()) {
+				return SortArray.sortArrayOf(fieldReference).by(direction);
+			}
+
+			return (usesExpression() ? SortArray.sortArrayOf(expression) : SortArray.sortArray(values)).by(direction);
+		}
+
 		/**
 		 * Creates new {@link AggregationExpression} that transposes an array of input arrays so that the first element of
 		 * the output array would be an array containing, the first element of the first input array, the first element of
@@ -2081,10 +2098,20 @@ public class ArrayOperators {
 			return new SortArray(append("sortBy", -1));
 		}
 
-		/*
+		/**
-		 * (non-Javadoc)
+		 * Set the order to put elements in.
-		 * @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#getMongoMethod()
+		 *
+		 * @param direction must not be {@literal null}.
+		 * @return new instance of {@link SortArray}.
 		 */
+		public SortArray by(Direction direction) {
+			return new SortArray(append("sortBy", direction.isAscending() ? 1 : -1));
+		}
+
+		/*
+		* (non-Javadoc)
+		* @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#getMongoMethod()
+		*/
 		@Override
 		protected String getMongoMethod() {
 			return "$sortArray";

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

@@ -24,6 +24,7 @@ import java.util.List;
 import org.bson.Document;
 import org.junit.jupiter.api.Test;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Sort.Direction;
 import org.springframework.data.mongodb.core.aggregation.ArrayOperators.ArrayToObject;
 import org.springframework.data.mongodb.core.aggregation.ArrayOperators.SortArray;
 
@@ -203,4 +204,12 @@ public class ArrayOperatorsUnitTests {
 				new Document("input", "$items").append("sortBy", new Document("price", 1)));
 		assertThat(result).isEqualTo(expected);
 	}
+
+	@Test // GH-4929
+	void sortByWithDirection() {
+
+		assertThat(ArrayOperators.arrayOf(List.of("a", "b", "d", "c")).sort(Direction.DESC)
+				.toDocument(Aggregation.DEFAULT_CONTEXT))
+				.isEqualTo("{ $sortArray: { input: [\"a\", \"b\", \"d\", \"c\"], sortBy: -1 } }");
+	}
 }