CSHARP-5629 Respect BsonElement attribute in NamedIdMemberConvention

src/MongoDB.Bson/Serialization/Conventions/NamedIdMemberConvention.cs

@@ -17,6 +17,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
+using MongoDB.Bson.Serialization.Attributes;
 
 namespace MongoDB.Bson.Serialization.Conventions
 {
@@ -119,6 +120,12 @@ private bool IsValidIdMember(BsonClassMap classMap, MemberInfo member)
                     return false;
                 }
             }
+
+            var bsonElement = member.GetCustomAttribute<BsonElementAttribute>();
+            if (bsonElement != null && !string.IsNullOrEmpty(bsonElement.ElementName) && bsonElement.ElementName != "_id")
+            {
+                return false;
+            }
             return true;
         }
     }

tests/MongoDB.Bson.Tests/Serialization/Conventions/ElementNameConventionsTests.cs

@@ -14,19 +14,83 @@
 */
 
 using MongoDB.Bson.Serialization;
+using MongoDB.Bson.Serialization.Attributes;
 using MongoDB.Bson.Serialization.Conventions;
 using Xunit;
 
 namespace MongoDB.Bson.Tests.Serialization.Conventions
 {
     public class ElementNameConventionsTests
     {
-        private class TestClass
+
+        [Fact]
+        public void TestBsonElementAttributeOverridesNamedIdMemberConvention()
         {
-            public string FirstName { get; set; }
-            public int Age { get; set; }
-            public string _DumbName { get; set; }
-            public string lowerCase { get; set; }
+            var classMap = new BsonClassMap<BookWithBsonElementAttribute>();
+            classMap.AutoMap();
+
+            classMap.Freeze();
+            Assert.Null(classMap.IdMemberMap);
+            Assert.Equal("notId", classMap.GetMemberMap(x => x.Id).ElementName);
+        }
+
+        [Fact]
+        public void TestBsonIdAttributeOverridesNamedIdMemberConvention()
+        {
+            var classMap = new BsonClassMap<BookWithBsonIdAttribute>();
+            classMap.AutoMap();
+
+            classMap.Freeze();
+            Assert.Equal("_id", classMap.GetMemberMap(x => x.Title).ElementName);
+            Assert.Equal("_id", classMap.IdMemberMap.ElementName);
+            Assert.Equal("Title", classMap.IdMemberMap.MemberName);
+            Assert.Equal("id", classMap.GetMemberMap(x => x.id).ElementName);
+        }
+
+        [Fact]
+        public void TestBsonIdAttributeWinsWhenBsonElementSkipsIdProperty()
+        {
+            var classMap = new BsonClassMap<BookWithBsonElementAndBsonId>();
+            classMap.AutoMap();
+            classMap.Freeze();
+
+            Assert.Equal("Title", classMap.IdMemberMap.MemberName);
+            Assert.Equal("notId", classMap.GetMemberMap(x => x.Id).ElementName);
+        }
+
+        [Fact]
+        public void TestBsonElementWithUnderscoreIdOnIdPropertyAlsoBecomesIdMember()
+        {
+            var classMap = new BsonClassMap<BookWithExplicitBsonElementId>();
+            classMap.AutoMap();
+            classMap.Freeze();
+
+            Assert.NotNull(classMap.IdMemberMap);
+            Assert.Equal("Id", classMap.IdMemberMap.MemberName);
+            Assert.Equal("_id", classMap.GetMemberMap(x => x.Id).ElementName);
+        }
+
+        [Fact]
+        public void TestBsonElementWithUnderscoreIdButNoIdPropertyDoesNotBecomeIdMember()
+        {
+            var classMap = new BsonClassMap<BookWithExplicitBsonElementIdButNoIdProperty>();
+            classMap.AutoMap();
+            classMap.Freeze();
+
+            Assert.Null(classMap.IdMemberMap);
+            Assert.Equal("_id", classMap.GetMemberMap(x => x.Title).ElementName);
+        }
+
+        [Fact]
+        public void TestBsonElementOnIdFallsThroughToLowercaseId()
+        {
+            var classMap = new BsonClassMap<BookWithBsonElementAndFallthrough>();
+            classMap.AutoMap();
+            classMap.Freeze();
+
+            Assert.Equal("id", classMap.IdMemberMap.MemberName);
+            Assert.Equal("_id", classMap.GetMemberMap(x => x.id).ElementName);
+            Assert.Equal("notId", classMap.GetMemberMap(x => x.Id).ElementName);
         }
 
         [Fact]
@@ -58,5 +122,55 @@ public void TestCamelCaseElementNameConvention()
             Assert.Equal("_DumbName", classMap.GetMemberMap(x => x._DumbName).ElementName);
             Assert.Equal("lowerCase", classMap.GetMemberMap(x => x.lowerCase).ElementName);
         }
+
+        private class BookWithBsonElementAttribute
+        {
+            [BsonElement("notId")]
+            public ObjectId Id { get; set; } // should not be set to _id
+        }
+
+        private class BookWithBsonIdAttribute
+        {
+            public ObjectId id { get; set; }
+
+            [BsonId]
+            public string Title { get; set; } // should be set to _id
+        }
+
+        private class BookWithBsonElementAndBsonId
+        {
+            [BsonElement("notId")]
+            public ObjectId Id { get; set; }
+
+            [BsonId]
+            public string Title { get; set; } // should be set to _id
+        }
+
+        private class BookWithExplicitBsonElementId
+        {
+            [BsonElement("_id")]
+            public string Id { get; set; } // should not be set to _id
+        }
+
+        private class BookWithExplicitBsonElementIdButNoIdProperty
+        {
+            [BsonElement("_id")]
+            public string Title { get; set; } // should be set to _id
+        }
+
+        private class BookWithBsonElementAndFallthrough
+        {
+            [BsonElement("notId")]
+            public ObjectId Id { get; set; }
+            public ObjectId id { get; set; } // should be set to _id
+        }
+
+        private class TestClass
+        {
+            public string FirstName { get; set; }
+            public int Age { get; set; }
+            public string _DumbName { get; set; }
+            public string lowerCase { get; set; }
+        }
     }
 }