Add support for $tsIncrement aggregation operator.

See #4139
Original pull request: #4182.

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

@@ -818,6 +818,21 @@ public class DateOperators {
 			return applyTimezone(DateFromString.fromString(dateReference()), timezone);
 		}
 
+		/**
+		 * Creates new {@link AggregationExpression} that returns the incrementing ordinal from a timestamp.
+		 *
+		 * @return new instance of {@link TsIncrement}.
+		 * @since 4.0
+		 */
+		public TsIncrement tsIncrement() {
+
+			if(timezone != null && !Timezone.none().equals(timezone)) {
+				throw new IllegalArgumentException("$tsIncrement does not support timezones");
+			}
+
+			return TsIncrement.tsIncrement(dateReference());
+		}
+
 		private Object dateReference() {
 
 			if (usesFieldRef()) {
@@ -3182,6 +3197,63 @@ public class DateOperators {
 		}
 	}
 
+	/**
+	 * {@link AggregationExpression} for {@code $tsIncrement}.
+	 *
+	 * @author Christoph Strobl
+	 * @since 4.0
+	 */
+	public static class TsIncrement extends AbstractAggregationExpression {
+
+		private TsIncrement(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link TsIncrement} that returns the incrementing ordinal from a timestamp.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link TsIncrement}.
+		 * @throws IllegalArgumentException if given {@literal value} is {@literal null}.
+		 */
+		public static TsIncrement tsIncrement(Object value) {
+
+			Assert.notNull(value, "Value must not be null");
+			return new TsIncrement(value);
+		}
+
+		/**
+		 * Creates new {@link TsIncrement} that returns the incrementing ordinal from a timestamp.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link TsIncrement}.
+		 * @throws IllegalArgumentException if given {@literal fieldReference} is {@literal null}.
+		 */
+		public static TsIncrement tsIncrementValueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null");
+			return tsIncrement(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link TsIncrement}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link TsIncrement}.
+		 * @throws IllegalArgumentException if given {@literal expression} is {@literal null}.
+		 */
+		public static TsIncrement tsIncrementValueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null");
+			return tsIncrement(expression);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$tsIncrement";
+		}
+	}
+
 	/**
 	 * Interface defining a temporal unit for date operators.
 	 *

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

@@ -191,6 +191,7 @@ public class MethodReferenceNode extends ExpressionNode {
 		map.put("isoDayOfWeek", singleArgRef().forOperator("$isoDayOfWeek"));
 		map.put("isoWeek", singleArgRef().forOperator("$isoWeek"));
 		map.put("isoWeekYear", singleArgRef().forOperator("$isoWeekYear"));
+		map.put("tsIncrement", singleArgRef().forOperator("$tsIncrement"));
 
 		// CONDITIONAL OPERATORS
 		map.put("cond", mapArgRef().forOperator("$cond") //

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

@@ -24,8 +24,6 @@ import java.time.temporal.ChronoUnit;
 import java.util.TimeZone;
 
 import org.junit.jupiter.api.Test;
-
-import org.springframework.data.mongodb.core.aggregation.DateOperators.TemporalUnit;
 import org.springframework.data.mongodb.core.aggregation.DateOperators.Timezone;
 
 /**
@@ -118,4 +116,18 @@ class DateOperatorsUnitTests {
 		assertThat(DateOperators.zonedDateOf("purchaseDate", Timezone.valueOf("America/Chicago")).truncate("week").binSize(2).startOfWeek(DayOfWeek.MONDAY).toDocument(Aggregation.DEFAULT_CONTEXT))
 				.isEqualTo("{ $dateTrunc: { date: \"$purchaseDate\", unit: \"week\", binSize: 2, startOfWeek : \"monday\", timezone : \"America/Chicago\" } }");
 	}
+
+	@Test // GH-4139
+	void rendersTsIncrement() {
+
+		assertThat(DateOperators.dateOf("saleTimestamp").tsIncrement().toDocument(Aggregation.DEFAULT_CONTEXT)).isEqualTo(
+						"{ $tsIncrement: \"$saleTimestamp\" }");
+	}
+
+	@Test // GH-4139
+	void tsIncrementErrorsOnTimezone() {
+
+		assertThatExceptionOfType(IllegalArgumentException.class)
+				.isThrownBy(() -> DateOperators.zonedDateOf("purchaseDate", Timezone.valueOf("America/Chicago")).tsIncrement());
+	}
 }

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

@@ -1241,6 +1241,11 @@ public class SpelExpressionTransformerUnitTests {
 				"sortArray(team, new org.bson.Document(\"name\" , 1))")).isEqualTo("{ $sortArray : { input : \"$team\", sortBy : {\"name\" : 1 } }}");
 	}
 
+	@Test // GH-4139
+	void shouldTsIncrement() {
+		assertThat(transform("tsIncrement(saleTimestamp)")).isEqualTo("{ $tsIncrement: \"$saleTimestamp\" }");
+	}
+	
 	private Document transform(String expression, Object... params) {
 		return (Document) transformer.transform(expression, Aggregation.DEFAULT_CONTEXT, params);
 	}