Fix property value conversion for $in clauses.

This commit fixes an issue where a property value converter is not applied if the query is using an $in clause that compares the value against a collection of potential candidates.

Original pull request: #4324
Closes #4080

Author: christophstrobl

Diff for: spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java

@@ -30,6 +30,8 @@
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.annotation.Reference;
+import org.springframework.data.convert.PropertyValueConverter;
+import org.springframework.data.convert.ValueConversionContext;
 import org.springframework.data.domain.Example;
 import org.springframework.data.mapping.Association;
 import org.springframework.data.mapping.MappingException;
@@ -435,9 +437,17 @@ protected Object getMappedValue(Field documentField, Object sourceValue) {
 
 		if (documentField.getProperty() != null
 				&& converter.getCustomConversions().hasValueConverter(documentField.getProperty())) {
-			return converter.getCustomConversions().getPropertyValueConversions()
-					.getValueConverter(documentField.getProperty())
-					.write(value, new MongoConversionContext(documentField.getProperty(), converter));
+
+			MongoConversionContext conversionContext = new MongoConversionContext(documentField.getProperty(), converter);
+			PropertyValueConverter<Object, Object, ValueConversionContext<MongoPersistentProperty>> valueConverter = converter
+					.getCustomConversions().getPropertyValueConversions().getValueConverter(documentField.getProperty());
+
+			/* might be an $in clause with multiple entries */
+			if (!documentField.getProperty().isCollectionLike() && sourceValue instanceof Collection<?> collection) {
+				return collection.stream().map(it -> valueConverter.write(it, conversionContext)).collect(Collectors.toList());
+			}
+
+			return valueConverter.write(value, conversionContext);
 		}
 
 		if (documentField.isIdField() && !documentField.isAssociation()) {

Diff for: spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java

@@ -1453,14 +1453,23 @@ void mapStringIdFieldProjection() {
 		assertThat(mappedQuery.get("_id"))
 				.isEqualTo(org.bson.Document.parse("{ $in: [ {$oid: \"5b8bedceb1e0bfc07b008828\" } ]}"));
 	}
-	
+
 	@Test // GH-3596
 	void considersValueConverterWhenPresent() {
 
 		org.bson.Document mappedObject = mapper.getMappedObject(new org.bson.Document("text", "value"), context.getPersistentEntity(WithPropertyValueConverter.class));
 		assertThat(mappedObject).isEqualTo(new org.bson.Document("text", "eulav"));
 	}
 
+	@Test // GH-4080
+	void convertsListOfValuesForPropertyThatHasValueConverterButIsNotCollectionLikeOneByOne() {
+
+		org.bson.Document mappedObject = mapper.getMappedObject(query(where("text").in("spring", "data")).getQueryObject(),
+				context.getPersistentEntity(WithPropertyValueConverter.class));
+
+		assertThat(mappedObject).isEqualTo("{ 'text' : { $in : ['gnirps', 'atad'] } }");
+	}
+
 	class WithDeepArrayNesting {
 
 		List<WithNestedArray> level0;
@@ -1739,9 +1748,9 @@ static class Customer {
 	static class MyAddress {
 		private String street;
 	}
-	
+
 	static class WithPropertyValueConverter {
-		
+
 		@ValueConverter(ReversingValueConverter.class)
 		String text;
 	}