JetStream config JSON fixed (#394)

* JetStream config JSON fixed

* Placement JSON test

* removed unused ifdef

* format

Author: mtmk

src/NATS.Client.JetStream/Models/Placement.cs

@@ -10,15 +10,8 @@ public record Placement
     /// The desired cluster name to place the stream
     /// </summary>
     [System.Text.Json.Serialization.JsonPropertyName("cluster")]
-    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.Never)]
-    [System.ComponentModel.DataAnnotations.Required(AllowEmptyStrings = true)]
-#if NET6_0
-    public string Cluster { get; set; } = default!;
-#else
-#pragma warning disable SA1206
-    public required string Cluster { get; set; }
-#pragma warning restore SA1206
-#endif
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public string? Cluster { get; set; }
 
     /// <summary>
     /// Tags required on servers hosting this stream

tests/NATS.Client.JetStream.Tests/ParseJsonTests.cs

@@ -0,0 +1,28 @@
+using System.Buffers;
+using System.Text;
+using NATS.Client.JetStream.Internal;
+using NATS.Client.JetStream.Models;
+
+namespace NATS.Client.JetStream.Tests;
+
+public class ParseJsonTests
+{
+    [Fact]
+    public void Placement_properties_should_be_optional()
+    {
+        // This is necessary because when a KV bucket created using nats client, the placement is not set
+        // and the server will return an empty object for placement.
+        var serializer = NatsJSJsonSerializer<Placement>.Default;
+
+        var bw = new NatsBufferWriter<byte>();
+        serializer.Serialize(bw, new Placement());
+
+        var json = Encoding.UTF8.GetString(bw.WrittenSpan);
+        Assert.Equal("{}", json);
+
+        var result = serializer.Deserialize(new ReadOnlySequence<byte>(bw.WrittenMemory));
+        Assert.NotNull(result);
+        Assert.Null(result.Cluster);
+        Assert.Null(result.Tags);
+    }
+}