CSHARP-3212: Add new field truncatedArrays into cursor.nextBatch.updateDescription.

Author: DmitryLukyanov

src/MongoDB.Driver.Core/ChangeStreamUpdateDescription.cs

@@ -13,6 +13,7 @@
 * limitations under the License.
 */
 
+using System;
 using System.Linq;
 using MongoDB.Bson;
 using MongoDB.Driver.Core.Misc;
@@ -27,6 +28,7 @@ public sealed class ChangeStreamUpdateDescription
     {
         // private fields
         private readonly string[] _removedFields;
+        private readonly BsonArray _truncatedArrays;
         private readonly BsonDocument _updatedFields;
 
         // constructors
@@ -38,9 +40,24 @@ public sealed class ChangeStreamUpdateDescription
         public ChangeStreamUpdateDescription(
             BsonDocument updatedFields,
             string[] removedFields)
+            : this(updatedFields, removedFields, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ChangeStreamUpdateDescription" /> class.
+        /// </summary>
+        /// <param name="updatedFields">The updated fields.</param>
+        /// <param name="removedFields">The removed fields.</param>
+        /// <param name="truncatedArrays">The truncated arrays.</param>
+        public ChangeStreamUpdateDescription(
+            BsonDocument updatedFields,
+            string[] removedFields,
+            BsonArray truncatedArrays)
         {
             _updatedFields = Ensure.IsNotNull(updatedFields, nameof(updatedFields));
             _removedFields = Ensure.IsNotNull(removedFields, nameof(removedFields));
+            _truncatedArrays = truncatedArrays; // can be null
         }
 
         // public properties
@@ -52,6 +69,14 @@ public ChangeStreamUpdateDescription(
         /// </value>
         public string[] RemovedFields => _removedFields;
 
+        /// <summary>
+        /// Gets the truncated arrays.
+        /// </summary>
+        /// <value>
+        /// The truncated arrays.
+        /// </value>
+        public BsonArray TruncatedArrays => _truncatedArrays;
+
         /// <summary>
         /// Gets the updated fields.
         /// </summary>
@@ -72,7 +97,8 @@ public override bool Equals(object obj)
             var other = (ChangeStreamUpdateDescription)obj;
             return
                 _removedFields.SequenceEqual(other._removedFields) &&
-                _updatedFields.Equals(other._updatedFields);
+                _updatedFields.Equals(other._updatedFields) &&
+                object.Equals(_truncatedArrays, other._truncatedArrays);
         }
 
         /// <inheritdoc />
@@ -81,6 +107,7 @@ public override int GetHashCode()
             return new Hasher()
                 .HashElements(_removedFields)
                 .Hash(_updatedFields)
+                .Hash(_truncatedArrays)
                 .GetHashCode();
         }
     }

src/MongoDB.Driver.Core/ChangeStreamUpdateDescriptionSerializer.cs

@@ -49,6 +49,7 @@ protected override ChangeStreamUpdateDescription DeserializeValue(BsonDeserializ
 
             BsonDocument updatedFields = null;
             string[] removedFields = null;
+            BsonArray truncatedArrays = null;
 
             reader.ReadStartDocument();
             while (reader.ReadBsonType() != 0)
@@ -64,13 +65,17 @@ protected override ChangeStreamUpdateDescription DeserializeValue(BsonDeserializ
                         removedFields = __stringArraySerializer.Deserialize(context);
                         break;
 
+                    case "truncatedArrays":
+                        truncatedArrays = BsonArraySerializer.Instance.Deserialize(context);
+                        break;
+
                     default:
                         throw new FormatException($"Invalid field name: \"{fieldName}\".");
                 }
             }
             reader.ReadEndDocument();
 
-            return new ChangeStreamUpdateDescription(updatedFields, removedFields);
+            return new ChangeStreamUpdateDescription(updatedFields, removedFields, truncatedArrays);
         }
 
         /// <inheritdoc />
@@ -83,6 +88,11 @@ protected override void SerializeValue(BsonSerializationContext context, BsonSer
             BsonDocumentSerializer.Instance.Serialize(context, value.UpdatedFields);
             writer.WriteName("removedFields");
             __stringArraySerializer.Serialize(context, value.RemovedFields);
+            if (value.TruncatedArrays != null)
+            {
+                writer.WriteName("truncatedArrays");
+                BsonArraySerializer.Instance.Serialize(context, value.TruncatedArrays);
+            }
             writer.WriteEndDocument();
         }
     }

tests/MongoDB.Driver.Core.Tests/ChangeStreamDocumentTests.cs

@@ -280,18 +280,26 @@ public void ResumeToken_should_return_null_when_not_present()
         }
 
         [Theory]
-        [InlineData("{}", new string[0])]
-        [InlineData("{ x : 1 }", new[] { "a", "b", "c" })]
-        public void UpdateDescription_should_return_expected_result(string updatedFieldsJson, string[] removedFields)
+        [InlineData("{}", new string[0], null)]
+        [InlineData("{ x : 1 }", new[] { "a", "b", "c" }, null)]
+        [InlineData("{ x : 1 }", new[] { "a", "b", "c" }, "[ ]")]
+        [InlineData("{ x : 1 }", new[] { "a", "b", "c" }, "[ { field : 'arrayForSubdiff', newSize : 2 } ]")]
+        public void UpdateDescription_should_return_expected_result(string updatedFieldsJson, string[] removedFields, string truncatedArrays)
         {
             var updatedFields = BsonDocument.Parse(updatedFieldsJson);
-            var updateDescriptionDocument = new BsonDocument { { "updatedFields", updatedFields }, { "removedFields", new BsonArray(removedFields) } };
+            var truncatedArraysBsonArray = truncatedArrays != null ? BsonSerializer.Deserialize<BsonArray>(truncatedArrays) : null;
+            var updateDescriptionDocument = new BsonDocument
+            {
+                { "updatedFields", updatedFields },
+                { "removedFields", new BsonArray(removedFields) },
+                { "truncatedArrays", truncatedArraysBsonArray, truncatedArraysBsonArray != null }
+            };
             var backingDocument = new BsonDocument { { "other", 1 }, { "updateDescription", updateDescriptionDocument } };
             var subject = CreateSubject(backingDocument: backingDocument);
 
             var result = subject.UpdateDescription;
 
-            var expectedResult = new ChangeStreamUpdateDescription(updatedFields, removedFields);
+            var expectedResult = new ChangeStreamUpdateDescription(updatedFields, removedFields, truncatedArraysBsonArray);
             result.Should().Be(expectedResult);
         }
 

tests/MongoDB.Driver.Core.Tests/ChangeStreamUpdateDescriptionSerializerTests.cs

@@ -28,6 +28,7 @@ public class ChangeStreamUpdateDescriptionSerializerTests
     {
         [Theory]
         [InlineData("{ updatedFields : { f : 1 }, removedFields : [\"f\"] }")]
+        [InlineData("{ updatedFields : { f : 1 }, removedFields : [\"f\"], truncatedArrays : [ { field : \"arrayForSubdiff\", newSize : 2 } ] }")]
         public void Deserialize_should_return_expected_result(
             string json)
         {
@@ -41,7 +42,7 @@ public void Deserialize_should_return_expected_result(
                 result = subject.Deserialize(context);
             }
 
-            result.ShouldBeEquivalentTo(expectedResult);
+            result.Should().Be(expectedResult);
         }
 
         [Fact]
@@ -83,8 +84,9 @@ public void Serialize_should_have_expected_result()
             var subject = CreateSubject();
             var value = new ChangeStreamUpdateDescription(
                 new BsonDocument("f", 1),
-                new[] { "f" });
-            var expectedResult = "{ \"updatedFields\" : { \"f\" : 1 }, \"removedFields\" : [\"f\"] }";
+                new[] { "f" },
+                BsonArray.Create(new[] { BsonDocument.Parse("{ field : 'arrayForSubdiff', newSize : 2 }") }));
+            var expectedResult = "{ \"updatedFields\" : { \"f\" : 1 }, \"removedFields\" : [\"f\"], \"truncatedArrays\" : [{ \"field\" : \"arrayForSubdiff\", \"newSize\" : 2 }] }";
 
             string result;
             using (var textWriter = new StringWriter())
@@ -127,8 +129,9 @@ private ChangeStreamUpdateDescription ParseUpdateDescription(string json)
             var document = BsonDocument.Parse(json);
             var updatedFields = document["updatedFields"].AsBsonDocument;
             var removedFields = document["removedFields"].AsBsonArray.Select(f => f.AsString).ToArray();
+            var truncatedArrays = document.GetValue("truncatedArrays", null)?.AsBsonArray;
 
-            return new ChangeStreamUpdateDescription(updatedFields, removedFields);
+            return new ChangeStreamUpdateDescription(updatedFields, removedFields, truncatedArrays);
         }
     }
 }