From d0bf0e2e623ac933c84c71572f064f2b4123de2c Mon Sep 17 00:00:00 2001
From: Christoph Strobl <cstrobl@vmware.com>
Date: Mon, 21 Jun 2021 12:24:02 +0200
Subject: [PATCH] Fix field projection value conversion.

The field projection conversion should actually only map field names and avoid value conversion. In the MongoId case an inclusion parameter (1) was unintentionally converted into its String representation which causes trouble on Mongo 4.4 servers.

Fixes: #3668
Original pull request: #3678.
---
 .../mongodb/core/convert/QueryMapper.java     | 37 +++++++++++--------
 .../core/convert/QueryMapperUnitTests.java    | 14 +++++++
 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java
index a248134f3..7e1411823 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java
@@ -194,19 +194,7 @@ public class QueryMapper {
 			return new Document();
 		}
 
-		sortObject = filterUnwrappedObjects(sortObject, entity);
-
-		Document mappedSort = new Document();
-		for (Map.Entry<String, Object> entry : BsonUtils.asMap(sortObject).entrySet()) {
-
-			Field field = createPropertyField(entity, entry.getKey(), mappingContext);
-			if (field.getProperty() != null && field.getProperty().isUnwrapped()) {
-				continue;
-			}
-
-			mappedSort.put(field.getMappedKey(), entry.getValue());
-		}
-
+		Document mappedSort = mapFieldsToPropertyNames(sortObject, entity);
 		mapMetaAttributes(mappedSort, entity, MetaMapping.WHEN_PRESENT);
 		return mappedSort;
 	}
@@ -224,13 +212,30 @@ public class QueryMapper {
 
 		Assert.notNull(fieldsObject, "FieldsObject must not be null!");
 
-		fieldsObject = filterUnwrappedObjects(fieldsObject, entity);
-
-		Document mappedFields = getMappedObject(fieldsObject, entity);
+		Document mappedFields = mapFieldsToPropertyNames(fieldsObject, entity);
 		mapMetaAttributes(mappedFields, entity, MetaMapping.FORCE);
 		return mappedFields;
 	}
 
+	private Document mapFieldsToPropertyNames(Document fields, @Nullable MongoPersistentEntity<?> entity) {
+
+		if (fields.isEmpty()) {
+			return new Document();
+
+		}
+		Document target = new Document();
+		for (Map.Entry<String, Object> entry : BsonUtils.asMap(filterUnwrappedObjects(fields, entity)).entrySet()) {
+
+			Field field = createPropertyField(entity, entry.getKey(), mappingContext);
+			if (field.getProperty() != null && field.getProperty().isUnwrapped()) {
+				continue;
+			}
+
+			target.put(field.getMappedKey(), entry.getValue());
+		}
+		return target;
+	}
+
 	private void mapMetaAttributes(Document source, @Nullable MongoPersistentEntity<?> entity, MetaMapping metaMapping) {
 
 		if (entity == null) {
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java
index 88ff08793..ceabbd6d7 100755
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java
@@ -55,6 +55,7 @@ import org.springframework.data.mongodb.core.mapping.DBRef;
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.data.mongodb.core.mapping.Field;
 import org.springframework.data.mongodb.core.mapping.FieldType;
+import org.springframework.data.mongodb.core.mapping.MongoId;
 import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.TextScore;
@@ -1302,6 +1303,13 @@ public class QueryMapperUnitTests {
 		assertThat(mapper.getMappedSort(query.getQueryObject(), context.getPersistentEntity(Customer.class))).isEqualTo(new org.bson.Document("address.street", "1007 Mountain Drive"));
 	}
 
+	@Test // GH-3668
+	void mapStringIdFieldProjection() {
+
+		org.bson.Document mappedFields = mapper.getMappedFields(new org.bson.Document("id", 1), context.getPersistentEntity(WithStringId.class));
+		assertThat(mappedFields).containsEntry("_id", 1);
+	}
+
 	class WithDeepArrayNesting {
 
 		List<WithNestedArray> level0;
@@ -1365,6 +1373,12 @@ public class QueryMapperUnitTests {
 		@Id private String foo;
 	}
 
+	class WithStringId {
+
+		@MongoId String id;
+		String name;
+	}
+
 	class BigIntegerId {
 
 		@Id private BigInteger id;