fix(csharp): emit value-object null-omission only on nullable members

fixtures/api-contract-conformance/jsonb/README.md

@@ -15,7 +15,7 @@ Java `Object`, Kotlin `JsonElement`, C# `JsonDocument`); this corpus locks it
 in cross-port.
 
 The single `Document` entity (`acme::store`, `@table="documents"`) carries an
-open-bag field plus three value-object columns:
+open-bag field plus four value-object columns:
 
 | Field            | Type                                                      | Notes                                    |
 |------------------|----------------------------------------------------------|------------------------------------------|
@@ -25,6 +25,7 @@ open-bag field plus three value-object columns:
 | `primaryMarker`  | `field.object @objectRef=Marker @storage=jsonb @required`| required single VO — present-null → 400   |
 | `optionalMarker` | `field.object @objectRef=Marker @storage=jsonb`          | nullable single VO — FR-035 tristate      |
 | `markers`        | `field.object @objectRef=Marker @storage=jsonb isArray`  | nullable array of VO — `[]` ≠ null        |
+| `telemetry`      | `field.object @objectRef=Telemetry @storage=jsonb`       | nullable VO with required non-nullable value types — see `jsonb-value-object-required-value-types` |
 
 **Why `id` is `@required`.** It is the shape every real model has — a shared
 `BaseEntity` declares `id` required — and the one no other api-contract entity
@@ -53,13 +54,14 @@ The `Marker` value object (`object.value`) is `{ label: field.string @required
 ```
 jsonb/
 ├── README.md              # this file
-├── meta.json              # the Document entity + Marker value object
+├── meta.json              # the Document entity + Marker and Telemetry value objects
 ├── seed.json              # 2 seed Documents (ids 1, 2), jsonb object + VO columns
 └── scenarios/
     ├── jsonb-open-bag-roundtrip.yaml   # open-bag parsed-value contract
     ├── jsonb-value-object-patch.yaml   # Program D — cross-port VO-column PATCH/POST
     ├── jsonb-value-object-map-decimals.yaml  # decimals in a field.map of value objects, per map value
-    └── jsonb-value-object-numbers.yaml # doubles and decimals inside a value object
+    ├── jsonb-value-object-numbers.yaml # doubles and decimals inside a value object
+    └── jsonb-value-object-required-value-types.yaml # required double + timestamp in a value object
 ```
 
 `seed.json` is applied fresh before the scenario; the runner advances the id
@@ -162,3 +164,18 @@ Amendment 1; see `../decimal/README.md`), per element for an array of value obje
 | `r10`/`r11` PATCH + GET | PATCH single `measure` (decimal as a number) is canonical, `measures` untouched |
 | `r12`-`r15` | PATCH array element canonicalized (`"3.10"` gives `"3.1"`); excess scale in an array element or in `measure` is `400` and the stored value is unchanged |
 | `r16`-`r18` PUT | PUT canonicalizes and persists; excess scale on PUT is `400` and nothing changes |
+
+## Scenario — `jsonb-value-object-required-value-types.yaml`
+
+A value object whose REQUIRED members are non-nullable value types in the native language
+(`Telemetry { capturedAt: field.timestamp @required; latitude: field.double @required; tempC:
+field.int }`, held by the nullable `Document.telemetry`). A port whose generated model cannot
+serialize or deserialize such a member answers every request that touches the owning entity
+with a 500 (C# emitted a null-omission condition on a non-nullable `double` /
+`DateTimeOffset`, which System.Text.Json rejects with `InvalidOperationException`;
+the condition is emitted on nullable members only).
+
+| Requests | What it pins |
+|---|---|
+| `r1`/`r2` POST + GET | create is `201`, the double stays a JSON number, the timestamp keeps its UTC `Z` spelling, `tempC` round-trips |
+| `r3`/`r4` PATCH + GET | PATCH replaces the value object (`tempC` omitted when absent) and it persists |

fixtures/api-contract-conformance/jsonb/meta.json

@@ -17,6 +17,14 @@
           { "field.decimal": { "name": "amount", "@precision": 12, "@scale": 4 } }
         ]
       }},
+      { "object.value": {
+        "name": "Telemetry",
+        "children": [
+          { "field.timestamp": { "name": "capturedAt", "@required": true } },
+          { "field.double":    { "name": "latitude", "@required": true } },
+          { "field.int":       { "name": "tempC" } }
+        ]
+      }},
       { "object.value": {
         "name": "Tier",
         "children": [
@@ -41,6 +49,7 @@
           { "field.object":     { "name": "markers",        "@objectRef": "Marker", "@storage": "jsonb", "isArray": true } },
           { "field.object":     { "name": "measure",  "@objectRef": "Measure", "@storage": "jsonb" } },
           { "field.object":     { "name": "measures", "@objectRef": "Measure", "@storage": "jsonb", "isArray": true } },
+          { "field.object":     { "name": "telemetry", "@objectRef": "Telemetry", "@storage": "jsonb" } },
           { "field.map":        { "name": "tiers", "@objectRef": "Tier" } },
           { "field.object":     { "name": "pricing", "@objectRef": "Pricing", "@storage": "jsonb" } },
           { "identity.primary": { "name": "id", "@fields": "id", "@generation": "increment" } }

fixtures/api-contract-conformance/jsonb/scenarios/jsonb-value-object-required-value-types.yaml

@@ -0,0 +1,50 @@
+name: jsonb-value-object-required-value-types
+description: >
+  A jsonb value object whose REQUIRED members are non-nullable value types (Telemetry:
+  `capturedAt` field.timestamp @required, `latitude` field.double @required, `tempC` field.int
+  optional), held by Document.telemetry. A port whose generated model refuses to serialize or
+  deserialize such a type answers every request that touches the owning entity with a 500
+  (System.Text.Json threw InvalidOperationException when a null-omission condition sat on a
+  non-nullable `double` / `DateTimeOffset`, so POST /api/documents answered 500). The contract: a
+  POST, the read-back and a PATCH all succeed, the double stays a JSON number, the timestamp keeps
+  its UTC `Z` spelling, and the optional `tempC` is omitted when absent. Implicit-id POSTs land at 3.
+requests:
+  - id: r1
+    method: POST
+    path: /api/documents
+    body:
+      title: "telemetry-a"
+      primaryMarker: { label: "a", score: 1 }
+      telemetry: { capturedAt: "2026-03-01T12:00:00Z", latitude: 51.5, tempC: 18 }
+    expect:
+      status: 201
+      body:
+        hasId: true
+        row:
+          telemetry: { capturedAt: "2026-03-01T12:00:00Z", latitude: 51.5, tempC: 18 }
+  - id: r2
+    method: GET
+    path: /api/documents/3
+    expect:
+      status: 200
+      body:
+        row:
+          telemetry: { capturedAt: "2026-03-01T12:00:00Z", latitude: 51.5, tempC: 18 }
+  - id: r3
+    method: PATCH
+    path: /api/documents/3
+    body:
+      telemetry: { capturedAt: "2026-03-02T08:30:00Z", latitude: -33.25 }
+    expect:
+      status: 200
+      body:
+        row:
+          telemetry: { capturedAt: "2026-03-02T08:30:00Z", latitude: -33.25 }
+  - id: r4
+    method: GET
+    path: /api/documents/3
+    expect:
+      status: 200
+      body:
+        row:
+          telemetry: { capturedAt: "2026-03-02T08:30:00Z", latitude: -33.25 }

server/csharp/MetaObjects.Codegen.Tests/ValueObjectWireIgnoreTests.cs

@@ -0,0 +1,76 @@
+using System.Reflection;
+using System.Text.Json;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using MetaObjects.Codegen;
+using MetaObjects.Codegen.Generators;
+using MetaObjects.Loader;
+using Xunit;
+
+namespace MetaObjects.Codegen.Tests;
+
+/// <summary>
+/// A value-object member that is null is omitted on the wire via
+/// <c>[JsonIgnore(WhenWritingNull)]</c>, but System.Text.Json throws InvalidOperationException
+/// the first time it builds type info for a type carrying that condition on a NON-nullable value
+/// type (<c>double</c>, <c>DateTimeOffset</c>), so every request that touched the owning entity
+/// answered 500. The condition belongs on the nullable members only.
+/// </summary>
+public class ValueObjectWireIgnoreTests
+{
+    private const string Model = """
+    { "metadata.root": { "package": "acme", "children": [
+      { "object.entity": { "name": "Leg", "children": [
+        { "source.rdb": { "@table": "legs" } },
+        { "field.long": { "name": "id" } },
+        { "field.object": { "name": "telemetry", "@objectRef": "acme::Telemetry", "@storage": "jsonb" } },
+        { "identity.primary": { "@fields": "id" } }
+      ]}},
+      { "object.value": { "name": "Telemetry", "children": [
+        { "field.timestamp": { "name": "capturedAt", "@required": true } },
+        { "field.double": { "name": "latitude", "@required": true } },
+        { "field.int": { "name": "tempC" } },
+        { "field.boolean": { "name": "live", "@required": true } },
+        { "field.decimal": { "name": "fee", "@required": true, "@precision": 10, "@scale": 2 } },
+        { "field.uuid": { "name": "token", "@required": true } },
+        { "field.string": { "name": "tags", "isArray": true } },
+        { "field.string": { "name": "note" } }
+      ]}}
+    ]}}
+    """;
+
+    [Fact]
+    public void A_value_object_with_required_value_type_members_round_trips_and_omits_a_null_optional_member()
+    {
+        var r = new MetaDataLoader().Load([new InMemoryStringSource(Model, id: "model.json")]);
+        Assert.Empty(r.Errors);
+        var files = new EntityGenerator().Generate(new GenContext
+        {
+            Entities = r.Root.Objects(),
+            Root = r.Root,
+            Config = new GenConfig { OutDir = "/tmp", Namespace = "Acme.Generated" },
+        });
+        var trees = files.Select(f => CSharpSyntaxTree.ParseText(f.Content, new CSharpParseOptions(LanguageVersion.CSharp12), path: f.Path));
+        var comp = CSharpCompilation.Create("vo_wire_ignore_" + Guid.NewGuid().ToString("N"), trees,
+            DbContextCompileTests.BuildReferences(), new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
+        using var ms = new MemoryStream();
+        var emit = comp.Emit(ms);
+        Assert.True(emit.Success, string.Join("\n", emit.Diagnostics.Where(d => d.Severity == DiagnosticSeverity.Error)));
+        var telemetry = Assembly.Load(ms.ToArray()).GetTypes().Single(t => t.Name == "Telemetry");
+
+        const string body = """
+            {"capturedAt":"2026-03-04T05:06:07Z","latitude":51.5,"live":true,"fee":"12.50","token":"3f2504e0-4f89-11d3-9a0c-0305e82c3301"}
+            """;
+        var value = JsonSerializer.Deserialize(body, telemetry)!;
+        Assert.Equal(51.5, telemetry.GetProperty("Latitude")!.GetValue(value));
+        Assert.Equal(DateTimeOffset.Parse("2026-03-04T05:06:07Z"), telemetry.GetProperty("CapturedAt")!.GetValue(value));
+        Assert.Null(telemetry.GetProperty("TempC")!.GetValue(value));
+
+        var wire = JsonDocument.Parse(JsonSerializer.Serialize(value, telemetry)).RootElement;
+        Assert.Equal(51.5, wire.GetProperty("latitude").GetDouble());
+        Assert.Equal(DateTimeOffset.Parse("2026-03-04T05:06:07Z"), wire.GetProperty("capturedAt").GetDateTimeOffset());
+        Assert.True(wire.GetProperty("live").GetBoolean());
+        Assert.False(wire.TryGetProperty("tempC", out _));
+        Assert.False(wire.TryGetProperty("note", out _));
+    }
+}

server/csharp/MetaObjects.Codegen/Generators/EntityGenerator.cs

@@ -852,8 +852,14 @@ protected virtual EmittedFile EmitValueObjectPoco(MetaObject vo, GenContext ctx)
             if (member is null) continue;
             // Pin the jsonb element name (+ wire name) to the metadata field name so the
             // stored owned-JSON keys match the shared seed + the cross-port wire contract.
-            // A null member is omitted on the wire (the cross-port value-object contract).
-            member = $"    [JsonPropertyName(\"{field.Name}\")]\n    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]\n" + member;
+            // A null member is omitted on the wire (the cross-port value-object contract). Only a
+            // NULLABLE member can be null, and System.Text.Json throws InvalidOperationException
+            // when WhenWritingNull sits on a non-nullable value type (double, DateTimeOffset, ...),
+            // so the condition is emitted for the nullable members alone.
+            var nullableMember = System.Text.RegularExpressions.Regex.IsMatch(member, @"^\s*public\s+[^=;{(]*\?\s+\w+", System.Text.RegularExpressions.RegexOptions.Multiline);
+            member = $"    [JsonPropertyName(\"{field.Name}\")]\n"
+                + (nullableMember ? "    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]\n" : "")
+                + member;
             member = ApplyPropertyAttributes(member, vo, field, ctx);
             members.Add(XmlDocBuilder.Prepend(member, field, "    "));
         }

server/csharp/MetaObjects.IntegrationTests/Api/JsonbFixture.cs

@@ -32,6 +32,7 @@ internal static class JsonbFixture
           "markers" jsonb,
           "measure" jsonb,
           "measures" jsonb,
+          "telemetry" jsonb,
           "tiers" jsonb,
           "pricing" jsonb,
           CONSTRAINT "documents_pkey" PRIMARY KEY ("id")
@@ -74,8 +75,8 @@ public static async Task ApplySeedAsync(string connString, string seedPath)
                 if (rowNode is not JsonObject row) continue;
                 await using var ins = c.CreateCommand();
                 ins.CommandText =
-                    "INSERT INTO \"documents\" (\"id\", \"title\", \"payload\", \"primaryMarker\", \"optionalMarker\", \"markers\", \"measure\", \"measures\", \"tiers\", \"pricing\") " +
-                    "VALUES (@id, @title, @payload, @primaryMarker, @optionalMarker, @markers, @measure, @measures, @tiers, @pricing)";
+                    "INSERT INTO \"documents\" (\"id\", \"title\", \"payload\", \"primaryMarker\", \"optionalMarker\", \"markers\", \"measure\", \"measures\", \"telemetry\", \"tiers\", \"pricing\") " +
+                    "VALUES (@id, @title, @payload, @primaryMarker, @optionalMarker, @markers, @measure, @measures, @telemetry, @tiers, @pricing)";
                 ins.Parameters.AddWithValue("@id", row["id"]!.GetValue<long>());
                 ins.Parameters.AddWithValue("@title", row["title"]!.GetValue<string>());
                 // payload + the VO columns are JSON — serialize each and bind as jsonb (an
@@ -87,6 +88,7 @@ public static async Task ApplySeedAsync(string connString, string seedPath)
                 AddJsonbParam(ins, "@markers", row["markers"]);
                 AddJsonbParam(ins, "@measure", row["measure"]);
                 AddJsonbParam(ins, "@measures", row["measures"]);
+                AddJsonbParam(ins, "@telemetry", row["telemetry"]);
                 AddJsonbParam(ins, "@tiers", row["tiers"]);
                 AddJsonbParam(ins, "@pricing", row["pricing"]);
                 await ins.ExecuteNonQueryAsync();

server/csharp/MetaObjects.IntegrationTests/Api/JsonbGeneratedServerFactory.cs

@@ -62,6 +62,10 @@ public static async Task<JsonbGeneratedServerFactory> StartAsync(PostgresContain
         builder.WebHost.UseUrls(baseUrl);
         builder.Logging.ClearProviders();
         RegisterGeneratedDbContext(builder.Services, dbContextType, pg.ConnectionString);
+        // The documented host registration: a field.timestamp crosses the wire as UTC with the Z
+        // designator (a Telemetry value object holds one).
+        builder.Services.ConfigureHttpJsonOptions(o =>
+            o.SerializerOptions.Converters.Add(new MetaObjects.Codegen.Runtime.Iso8601TimestampConverter()));
 
         var app = builder.Build();
 

server/csharp/MetaObjects.IntegrationTests/Api/JsonbReferenceServer.cs

@@ -41,7 +41,7 @@ internal sealed class JsonbReferenceServer : IAsyncDisposable
     private const int MarkerLabelMaxLength = 40;
 
     // The jsonb columns carried in a document row's wire projection (id + title are scalar).
-    private static readonly string[] JsonbColumns = { "payload", "primaryMarker", "optionalMarker", "markers", "measure", "measures", "tiers", "pricing" };
+    private static readonly string[] JsonbColumns = { "payload", "primaryMarker", "optionalMarker", "markers", "measure", "measures", "telemetry", "tiers", "pricing" };
 
     private JsonbReferenceServer(PostgresContainer pg, HttpListener listener, string baseUrl)
     {
@@ -160,15 +160,16 @@ private async Task CreateDocumentAsync(HttpListenerContext ctx)
         await using (var ins = c.CreateCommand())
         {
             ins.CommandText =
-                "INSERT INTO \"documents\" (\"title\", \"payload\", \"primaryMarker\", \"optionalMarker\", \"markers\", \"measure\", \"measures\", \"tiers\", \"pricing\") " +
-                "VALUES (@title, @payload, @primaryMarker, @optionalMarker, @markers, @measure, @measures, @tiers, @pricing) RETURNING id";
+                "INSERT INTO \"documents\" (\"title\", \"payload\", \"primaryMarker\", \"optionalMarker\", \"markers\", \"measure\", \"measures\", \"telemetry\", \"tiers\", \"pricing\") " +
+                "VALUES (@title, @payload, @primaryMarker, @optionalMarker, @markers, @measure, @measures, @telemetry, @tiers, @pricing) RETURNING id";
             ins.Parameters.AddWithValue("@title", body["title"]!.GetValue<string>());
             AddJsonbParam(ins, "@payload", body["payload"]);
             AddJsonbParam(ins, "@primaryMarker", body["primaryMarker"]);
             AddJsonbParam(ins, "@optionalMarker", body["optionalMarker"]);
             AddJsonbParam(ins, "@markers", body["markers"]);
             AddJsonbParam(ins, "@measure", body["measure"]);
             AddJsonbParam(ins, "@measures", body["measures"]);
+            AddJsonbParam(ins, "@telemetry", body["telemetry"]);
             AddJsonbParam(ins, "@tiers", body["tiers"]);
             AddJsonbParam(ins, "@pricing", body["pricing"]);
             newId = Convert.ToInt64(await ins.ExecuteScalarAsync());

server/csharp/MetaObjects.IntegrationTests/Generated/ProgramBrief.g.cs

@@ -12,7 +12,6 @@ namespace MetaObjects.IntegrationTests.Generated;
 public class ProgramBrief
 {
     [JsonPropertyName("title")]
-    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
     [Required(AllowEmptyStrings = true)]
     [MaxLength(200)]
     [MinLength(1)]

server/csharp/MetaObjects.IntegrationTests/Generated/ProgramVerdict.g.cs

@@ -13,10 +13,8 @@ public class ProgramVerdict
 {
     public enum ProgramVerdictVerdict { GOOD, OK, POOR }
     [JsonPropertyName("verdict")]
-    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
     public ProgramVerdictVerdict Verdict { get; set; }
     [JsonPropertyName("rationale")]
-    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
     [Required(AllowEmptyStrings = true)]
     [MaxLength(480)]
     [MinLength(1)]

server/csharp/MetaObjects.IntegrationTests/Generated/WeekLabel.g.cs

@@ -12,7 +12,6 @@ namespace MetaObjects.IntegrationTests.Generated;
 public class WeekLabel
 {
     [JsonPropertyName("label")]
-    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
     [Required(AllowEmptyStrings = true)]
     [MaxLength(80)]
     [MinLength(1)]