Avoid nested Document conversion to primitive types for fields with an explicit write target.

We now no longer attempt to convert query Documents into primitive types to avoid e.g. Document to String conversion.

Closes: #3783
Original Pull Request: #3797

Author: mp911de

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

@@ -778,7 +778,8 @@ protected boolean isKeyword(String candidate) {
 	@Nullable
 	private Object applyFieldTargetTypeHintToValue(Field documentField, @Nullable Object value) {
 
-		if (value == null || documentField.getProperty() == null || !documentField.getProperty().hasExplicitWriteTarget()) {
+		if (value == null || documentField.getProperty() == null || !documentField.getProperty().hasExplicitWriteTarget()
+				|| value instanceof Document || value instanceof DBObject) {
 			return value;
 		}
 

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

@@ -33,8 +33,7 @@
 import org.bson.types.ObjectId;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
-import org.mockito.junit.jupiter.MockitoExtension;
+
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.annotation.Id;
 import org.springframework.data.annotation.Transient;
@@ -83,9 +82,12 @@ public class QueryMapperUnitTests {
 	@BeforeEach
 	void beforeEach() {
 
+		MongoCustomConversions conversions = new MongoCustomConversions();
 		this.context = new MongoMappingContext();
+		this.context.setSimpleTypeHolder(conversions.getSimpleTypeHolder());
 
 		this.converter = new MappingMongoConverter(NoOpDbRefResolver.INSTANCE, context);
+		this.converter.setCustomConversions(conversions);
 		this.converter.afterPropertiesSet();
 
 		this.mapper = new QueryMapper(converter);
@@ -1335,6 +1337,25 @@ void mapStringIdFieldProjection() {
 		assertThat(mappedFields).containsEntry("_id", 1);
 	}
 
+	@Test // GH-3783
+	void retainsId$InWithStringArray() {
+
+		org.bson.Document mappedQuery = mapper.getMappedObject(
+				org.bson.Document.parse("{ _id : { $in: [\"5b8bedceb1e0bfc07b008828\"]}}"),
+				context.getPersistentEntity(WithExplicitStringId.class));
+		assertThat(mappedQuery.get("_id")).isEqualTo(org.bson.Document.parse("{ $in: [\"5b8bedceb1e0bfc07b008828\"]}"));
+	}
+
+	@Test // GH-3783
+	void mapsId$InInToObjectIds() {
+
+		org.bson.Document mappedQuery = mapper.getMappedObject(
+				org.bson.Document.parse("{ _id : { $in: [\"5b8bedceb1e0bfc07b008828\"]}}"),
+				context.getPersistentEntity(ClassWithDefaultId.class));
+		assertThat(mappedQuery.get("_id"))
+				.isEqualTo(org.bson.Document.parse("{ $in: [ {$oid: \"5b8bedceb1e0bfc07b008828\" } ]}"));
+	}
+
 	class WithDeepArrayNesting {
 
 		List<WithNestedArray> level0;
@@ -1404,6 +1425,12 @@ class WithStringId {
 		String name;
 	}
 
+	class WithExplicitStringId {
+
+		@MongoId(FieldType.STRING) String id;
+		String name;
+	}
+
 	class BigIntegerId {
 
 		@Id private BigInteger id;