CSHARP-1291: And and Or filter builder methods should handle zero clauses correctly.

Author: rstam

src/MongoDB.Driver/FilterDefinitionBuilder.cs

@@ -1503,6 +1503,11 @@ 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

@@ -131,6 +131,16 @@ public void And_with_a_nested_and_and_clashing_keys_using_ampersand()
             Assert(filter, "{$and: [{a: 1}, {a: 2}, {c: 3}]}");
         }
 
+        [Fact]
+        public void And_with_no_clauses()
+        {
+            var subject = CreateSubject<BsonDocument>();
+
+            var filter = subject.And();
+
+            Assert(filter, "{ $and : [] }");
+        }
+
         [Fact]
         public void BitsAllClear()
         {
@@ -830,6 +840,26 @@ public void Or_should_flatten_nested_ors_with_a_pipe()
             Assert(filter, "{$or: [{a: 1}, {b: 2}, {c: 3}]}");
         }
 
+        [Fact]
+        public void Or_with_no_clauses()
+        {
+            var subject = CreateSubject<BsonDocument>();
+
+            var filter = subject.Or();
+
+            Assert(filter, "{ $or : [] }");
+        }
+
+        [Fact]
+        public void Nor_with_no_clauses()
+        {
+            var subject = CreateSubject<BsonDocument>();
+
+            var filter = subject.Not(subject.Or());
+
+            Assert(filter, "{ $nor : [] }");
+        }
+
         [Fact]
         public void Regex()
         {