CSHARP-3614: Verify that issue is not present in LINQ3.

Author: rstam

tests/MongoDB.Driver.Tests/Linq/Linq3ImplementationTests/Jira/CSharp3614Tests.cs

@@ -0,0 +1,101 @@
+/* Copyright 2010-present MongoDB Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using System;
+using System.Linq;
+using FluentAssertions;
+using Xunit;
+
+namespace MongoDB.Driver.Tests.Linq.Linq3ImplementationTests.Jira
+{
+    public class CSharp3614Tests : Linq3IntegrationTest
+    {
+        [Fact]
+        public void Test()
+        {
+            var collection = CreateBooksCollection();
+
+            var queryable = collection.AsQueryable()
+                .Select(x => new BookDto
+                {
+                    Id = x.Id,
+                    PageCount = x.PageCount,
+                    Author = x.Author == null
+                        ? null
+                        : new AuthorDto
+                        {
+                            Id = x.Author.Id,
+                            Name = x.Author.Name
+                        }
+                });
+
+            var stages = Translate(collection, queryable);
+            AssertStages(stages, "{ $project : { _id : '$_id', PageCount : '$PageCount', Author : { $cond : { if : { $eq : ['$Author', null] }, then : null, else : { _id : '$Author._id', Name : '$Author.Name' } } } } }");
+
+            var results = queryable.ToList().OrderBy(r => r.Id).ToList();
+            results.Should().HaveCount(2);
+            results[0].Should().BeOfType<BookDto>();
+            results[0].Id.Should().Be(1);
+            results[0].PageCount.Should().Be(1);
+            results[0].Author.Should().BeNull();
+            results[1].Should().BeOfType<BookDto>();
+            results[1].Id.Should().Be(2);
+            results[1].PageCount.Should().Be(2);
+            results[1].Author.Should().BeOfType<AuthorDto>();
+            results[1].Author.ShouldBeEquivalentTo(new AuthorDto { Id = 2, Name = "Two" });
+        }
+
+        private IMongoCollection<Book> CreateBooksCollection()
+        {
+            var collection = GetCollection<Book>();
+
+            var documents = new[]
+            {
+                new Book { Id = 1, PageCount = 1, Author = null },
+                new Book { Id = 2, PageCount = 2, Author = new Author { Id = 2, Name = "Two" } }
+            };
+            CreateCollection(collection, documents);
+
+            return collection;
+        }
+
+        private class BookDto
+        {
+            public int Id { get; set; }
+            public int PageCount { get; set; }
+            public AuthorDto Author { get; set; }
+        }
+
+        private class AuthorDto
+        {
+            public int Id { get; set; }
+            public string Name { get; set; }
+        }
+
+        private class Author : IEquatable<Author>
+        {
+            public int Id { get; set; }
+            public string Name { get; set; }
+            public bool Equals(Author other) => Id == other.Id && Name == other.Name;
+        }
+
+        private class Book
+        {
+            public int Id { get; set; }
+            public int PageCount { get; set; }
+            public Author Author { get; set; }
+        }
+    }
+}