fix(generator): preserve effective schema metadata

packages/ack_generator/CHANGELOG.md

@@ -2,6 +2,12 @@
 
 ### Fixed
 
+* Preserve schema-first presence, nullability, and default-wrapper behavior
+  through aliases and explicit constant flag overrides. Apply the outermost
+  strict/passthrough policy to object models and aliases.
+* Reject object shape-changing methods that cannot be modeled statically,
+  instead of generating fields that disagree with the authored schema.
+
 * Allow built-in and contextual Dart keywords such as `required` as generated
   field, discriminator, and capture-member names without changing their JSON
   keys. Reserved words such as `class` remain rejected. Member validation now

packages/ack_generator/README.md

@@ -263,6 +263,15 @@ Named model references work through direct imports, prefixes, and re-exports.
 Nested conversion uses each model's public `$ack` adapter so codec runtime
 values aren't parsed twice.
 
+Schema-first fields retain optional, nullable, and default behavior through
+named schema variables and getters. Explicit constant flag overrides such as
+`.optional(value: false)` are honored, as is the outermost `.strict()` or
+`.passthrough()` object policy. Shape-changing object methods (`extend`,
+`partial`, `merge`, `pick`, `omit`, or `copyWith(properties: ...)`) are rejected
+when generating an object model; write its final properties in an
+`Ack.object({...})` map literal instead. An outer bidirectional codec can still
+wrap such a schema as a value model.
+
 ## Generated part
 
 Every annotated library declares a single `.g.dart` part:

packages/ack_generator/lib/src/analyzer/model_graph_builder_base.dart

@@ -17,18 +17,12 @@ final class SchemaChain {
   const SchemaChain({
     required this.base,
     required this.reference,
-    required this.optional,
-    required this.nullable,
-    required this.defaulted,
     required this.hasTransform,
     required this.hasCodec,
   });
 
   final MethodInvocation? base;
   final Expression? reference;
-  final bool optional;
-  final bool nullable;
-  final bool defaulted;
   final bool hasTransform;
   final bool hasCodec;
 }
@@ -677,26 +671,17 @@ abstract base class ModelGraphBuilderBase {
       return SchemaChain(
         base: null,
         reference: expression,
-        optional: false,
-        nullable: false,
-        defaulted: false,
         hasTransform: false,
         hasCodec: false,
       );
     }
     MethodInvocation? current = expression;
     MethodInvocation? base;
     Expression? reference;
-    var optional = false;
-    var nullable = false;
-    var defaulted = false;
     var transform = false;
     var codec = false;
     while (current != null) {
       final name = current.methodName.name;
-      optional |= name == 'optional';
-      nullable |= name == 'nullable';
-      defaulted |= name == 'withDefault';
       transform |= oneWayTransformMethods.contains(name);
       codec |= name == 'codec';
       if (current.methodName.element is TopLevelFunctionElement ||
@@ -719,9 +704,6 @@ abstract base class ModelGraphBuilderBase {
     return SchemaChain(
       base: base,
       reference: reference,
-      optional: optional,
-      nullable: nullable,
-      defaulted: defaulted,
       hasTransform: transform,
       hasCodec: codec,
     );