CSHARP-1912: And with one or more empty clauses rendering incorrectly.

Author: rstam

src/MongoDB.Driver/FilterDefinitionBuilder.cs

@@ -1492,6 +1492,11 @@ public AndFilterDefinition(IEnumerable<FilterDefinition<TDocument>> filters)
 
         public override BsonDocument Render(IBsonSerializer<TDocument> documentSerializer, IBsonSerializerRegistry serializerRegistry)
         {
+            if (_filters.Count == 0)
+            {
+                return new BsonDocument("$and", new BsonArray(0));
+            }
+
             var document = new BsonDocument();
 
             foreach (var filter in _filters)
@@ -1503,11 +1508,6 @@ public override BsonDocument Render(IBsonSerializer<TDocument> documentSerialize
                 }
             }
 
-            if (document.ElementCount == 0)
-            {
-                document = new BsonDocument("$and", new BsonArray(0));
-            }
-
             return document;
         }
 

tests/MongoDB.Driver.Tests/FilterDefinitionBuilderTests.cs

@@ -141,6 +141,28 @@ public void And_with_no_clauses()
             Assert(filter, "{ $and : [] }");
         }
 
+        [Fact]
+        public void And_with_one_empty_clause()
+        {
+            var subject = CreateSubject<BsonDocument>();
+            var empty = Builders<BsonDocument>.Filter.Empty;
+
+            var filter = subject.And(empty);
+
+            Assert(filter, "{ }");
+        }
+
+        [Fact]
+        public void And_with_two_empty_clauses()
+        {
+            var subject = CreateSubject<BsonDocument>();
+            var empty = Builders<BsonDocument>.Filter.Empty;
+
+            var filter = subject.And(empty, empty);
+
+            Assert(filter, "{ }");
+        }
+
         [Fact]
         public void BitsAllClear()
         {
@@ -904,6 +926,28 @@ public void Or_with_no_clauses()
             Assert(filter, "{ $or : [] }");
         }
 
+        [Fact]
+        public void Or_with_one_empty_clause()
+        {
+            var subject = CreateSubject<BsonDocument>();
+            var empty = Builders<BsonDocument>.Filter.Empty;
+
+            var filter = subject.Or(empty);
+
+            Assert(filter, "{ $or : [{}] }");
+        }
+
+        [Fact]
+        public void Or_with_two_empty_clauses()
+        {
+            var subject = CreateSubject<BsonDocument>();
+            var empty = Builders<BsonDocument>.Filter.Empty;
+
+            var filter = subject.Or(empty, empty);
+
+            Assert(filter, "{ $or : [{}, {}] }");
+        }
+
         [Fact]
         public void Nor_with_no_clauses()
         {