fix(platform_interface): restore copyWith() data preservation with shared unset sentinel

CLAUDE.md

@@ -48,6 +48,7 @@ When upgrading a toolkit, move all three platforms together where API surface ov
 - **Bridge serialization**: Readium-owned objects (`Locator`, `Decoration`, …) → JSON strings via `json.encode`; plugin-owned flat structures (preferences, action configs) → Maps. Rationale + Web-TS `.serialize()` rules: `docs/architecture.md#bridge-serialization`.
 - **Models**: hand-written `toJson`/`fromJson`. No `json_serializable`/`freezed`/build_runner codegen — don't reintroduce.
 - **PDF locator**: position = 1-based page in `Locator.locations.position` (matches upstream); don't invent plugin-side parallels to upstream models. Detail: `docs/api-reference/locator.md#pdf-locators`.
+- **copyWith sentinel**: use the shared `const unset` from `utils/constants.dart` for parameters that default to "not set" — never declare a new `_unset = Object()`. Merge additional-properties via `AdditionalProperties.copyAdditionalProperties()` instead of inline merge logic.
 
 ### Android
 

flutter_readium_platform_interface/lib/src/reader/audio_recovery_policy.dart

@@ -1,5 +1,6 @@
 import 'package:equatable/equatable.dart';
 import 'package:meta/meta.dart';
+import '../utils/constants.dart';
 
 /// Configures the automatic audio-stream error recovery loop (retry attempts,
 /// backoff, and stall detection) shared by the iOS/Android/web audio
@@ -59,15 +60,19 @@ class AudioRecoveryPolicy with Equatable {
   };
 
   AudioRecoveryPolicy copyWith({
-    int? maxAttempts,
-    double? backoffBaseSeconds,
-    double? stallTimeoutSeconds,
-    double? connectionTimeoutSeconds,
+    Object? maxAttempts = unset,
+    Object? backoffBaseSeconds = unset,
+    Object? stallTimeoutSeconds = unset,
+    Object? connectionTimeoutSeconds = unset,
   }) => AudioRecoveryPolicy(
-    maxAttempts: maxAttempts ?? this.maxAttempts,
-    backoffBaseSeconds: backoffBaseSeconds ?? this.backoffBaseSeconds,
-    stallTimeoutSeconds: stallTimeoutSeconds ?? this.stallTimeoutSeconds,
-    connectionTimeoutSeconds: connectionTimeoutSeconds ?? this.connectionTimeoutSeconds,
+    maxAttempts: identical(maxAttempts, unset) ? this.maxAttempts : (maxAttempts as int),
+    backoffBaseSeconds: identical(backoffBaseSeconds, unset) ? this.backoffBaseSeconds : (backoffBaseSeconds as double),
+    stallTimeoutSeconds: identical(stallTimeoutSeconds, unset)
+        ? this.stallTimeoutSeconds
+        : (stallTimeoutSeconds as double),
+    connectionTimeoutSeconds: identical(connectionTimeoutSeconds, unset)
+        ? this.connectionTimeoutSeconds
+        : (connectionTimeoutSeconds as double),
   );
 
   @override

flutter_readium_platform_interface/lib/src/reader/reader_audio_preferences.dart

@@ -132,25 +132,33 @@ class AudioPreferences with Equatable implements JSONable {
   ];
 
   AudioPreferences copyWith({
-    double? volume,
-    double? speed,
-    double? pitch,
-    double? seekInterval,
-    bool? continuousSeeking,
-    bool? allowExternalSeeking,
-    double? updateIntervalSecs,
-    ControlPanelInfoType? controlPanelInfoType,
-    ControlPanelTimebase? controlPanelTimebase,
+    Object? volume = unset,
+    Object? speed = unset,
+    Object? pitch = unset,
+    Object? seekInterval = unset,
+    Object? continuousSeeking = unset,
+    Object? allowExternalSeeking = unset,
+    Object? updateIntervalSecs = unset,
+    Object? controlPanelInfoType = unset,
+    Object? controlPanelTimebase = unset,
   }) => AudioPreferences(
-    volume: volume ?? this.volume,
-    speed: speed ?? this.speed,
-    pitch: pitch ?? this.pitch,
-    seekInterval: seekInterval ?? this.seekInterval,
-    continuousSeeking: continuousSeeking ?? this.continuousSeeking,
-    allowExternalSeeking: allowExternalSeeking ?? this.allowExternalSeeking,
-    updateIntervalSecs: updateIntervalSecs ?? this.updateIntervalSecs,
-    controlPanelInfoType: controlPanelInfoType ?? this.controlPanelInfoType,
-    controlPanelTimebase: controlPanelTimebase ?? this.controlPanelTimebase,
+    volume: identical(volume, unset) ? this.volume : (volume as double?)!,
+    speed: identical(speed, unset) ? this.speed : (speed as double?)!,
+    pitch: identical(pitch, unset) ? this.pitch : (pitch as double?)!,
+    seekInterval: identical(seekInterval, unset) ? this.seekInterval : (seekInterval as double?)!,
+    continuousSeeking: identical(continuousSeeking, unset) ? this.continuousSeeking : (continuousSeeking as bool?),
+    allowExternalSeeking: identical(allowExternalSeeking, unset)
+        ? this.allowExternalSeeking
+        : (allowExternalSeeking as bool?),
+    updateIntervalSecs: identical(updateIntervalSecs, unset)
+        ? this.updateIntervalSecs
+        : (updateIntervalSecs as double?)!,
+    controlPanelInfoType: identical(controlPanelInfoType, unset)
+        ? this.controlPanelInfoType
+        : (controlPanelInfoType as ControlPanelInfoType?)!,
+    controlPanelTimebase: identical(controlPanelTimebase, unset)
+        ? this.controlPanelTimebase
+        : (controlPanelTimebase as ControlPanelTimebase?)!,
   );
 }
 

flutter_readium_platform_interface/lib/src/reader/reader_decoration.dart

@@ -50,8 +50,11 @@ class ReaderDecoration implements JSONable {
   @override
   Map<String, dynamic> toJson() => {'id': id, 'locator': locator.toJson(), 'style': style.toJson()};
 
-  ReaderDecoration copyWith({String? id, Locator? locator, ReaderDecorationStyle? style}) =>
-      ReaderDecoration(id: id ?? this.id, locator: locator ?? this.locator, style: style ?? this.style);
+  ReaderDecoration copyWith({Object? id = unset, Object? locator = unset, Object? style = unset}) => ReaderDecoration(
+    id: identical(id, unset) ? this.id : (id as String?)!,
+    locator: identical(locator, unset) ? this.locator : (locator as Locator?)!,
+    style: identical(style, unset) ? this.style : (style as ReaderDecorationStyle?)!,
+  );
 }
 
 class ReaderDecorationStyle implements JSONable {
@@ -86,9 +89,10 @@ class ReaderDecorationStyle implements JSONable {
     isActive: map['isActive'] as bool? ?? false,
   );
 
-  ReaderDecorationStyle copyWith({DecorationStyle? style, Color? tint, bool? isActive}) => ReaderDecorationStyle(
-    style: style ?? this.style,
-    tint: tint ?? this.tint,
-    isActive: isActive ?? this.isActive,
-  );
+  ReaderDecorationStyle copyWith({Object? style = unset, Object? tint = unset, Object? isActive = unset}) =>
+      ReaderDecorationStyle(
+        style: identical(style, unset) ? this.style : (style as DecorationStyle?)!,
+        tint: identical(tint, unset) ? this.tint : tint as Color?,
+        isActive: identical(isActive, unset) ? this.isActive : (isActive as bool),
+      );
 }

flutter_readium_platform_interface/lib/src/reader/reader_pdf_preferences.dart

@@ -84,21 +84,23 @@ class PDFPreferences with Equatable implements JSONable {
     ..putOpt('visibleScrollbar', visibleScrollbar);
 
   PDFPreferences copyWith({
-    PDFLayout? layout,
-    PDFReadingProgression? readingProgression,
-    double? pageSpacing,
-    PDFFit? fit,
-    bool? offsetFirstPage,
-    PDFSpread? spread,
-    bool? visibleScrollbar,
+    Object? layout = unset,
+    Object? readingProgression = unset,
+    Object? pageSpacing = unset,
+    Object? fit = unset,
+    Object? offsetFirstPage = unset,
+    Object? spread = unset,
+    Object? visibleScrollbar = unset,
   }) => PDFPreferences(
-    layout: layout ?? this.layout,
-    readingProgression: readingProgression ?? this.readingProgression,
-    pageSpacing: pageSpacing ?? this.pageSpacing,
-    fit: fit ?? this.fit,
-    offsetFirstPage: offsetFirstPage ?? this.offsetFirstPage,
-    spread: spread ?? this.spread,
-    visibleScrollbar: visibleScrollbar ?? this.visibleScrollbar,
+    layout: identical(layout, unset) ? this.layout : (layout as PDFLayout?)!,
+    readingProgression: identical(readingProgression, unset)
+        ? this.readingProgression
+        : (readingProgression as PDFReadingProgression?)!,
+    pageSpacing: identical(pageSpacing, unset) ? this.pageSpacing : (pageSpacing as double?)!,
+    fit: identical(fit, unset) ? this.fit : (fit as PDFFit?)!,
+    offsetFirstPage: identical(offsetFirstPage, unset) ? this.offsetFirstPage : (offsetFirstPage as bool?),
+    spread: identical(spread, unset) ? this.spread : (spread as PDFSpread?),
+    visibleScrollbar: identical(visibleScrollbar, unset) ? this.visibleScrollbar : (visibleScrollbar as bool?),
   );
 
   @override

flutter_readium_platform_interface/lib/src/reader/reader_tts_voice.dart

@@ -2,6 +2,7 @@ import 'package:equatable/equatable.dart';
 import 'package:meta/meta.dart';
 
 import '../enums.dart';
+import '../utils/constants.dart';
 import '../utils/jsonable.dart';
 import '../utils/readium_log.dart';
 import 'index.dart';
@@ -119,20 +120,20 @@ class ReaderTTSVoice with Equatable implements JSONable {
   ];
 
   ReaderTTSVoice copyWith({
-    String? identifier,
-    String? name,
-    String? language,
-    bool? networkRequired,
-    TTSVoiceGender? gender,
-    TTSVoiceQuality? quality,
-    bool? active,
+    Object? identifier = unset,
+    Object? name = unset,
+    Object? language = unset,
+    Object? networkRequired = unset,
+    Object? gender = unset,
+    Object? quality = unset,
+    Object? active = unset,
   }) => ReaderTTSVoice(
-    identifier: identifier ?? this.identifier,
-    name: name ?? this.name,
-    language: language ?? this.language,
-    networkRequired: networkRequired ?? this.networkRequired,
-    gender: gender ?? this.gender,
-    quality: quality ?? this.quality,
-    active: active ?? this.active,
+    identifier: identical(identifier, unset) ? this.identifier : (identifier as String?)!,
+    name: identical(name, unset) ? this.name : (name as String?)!,
+    language: identical(language, unset) ? this.language : (language as String?)!,
+    networkRequired: identical(networkRequired, unset) ? this.networkRequired : (networkRequired as bool),
+    gender: identical(gender, unset) ? this.gender : (gender as TTSVoiceGender),
+    quality: identical(quality, unset) ? this.quality : (quality as TTSVoiceQuality?),
+    active: identical(active, unset) ? this.active : (active as bool?),
   );
 }

flutter_readium_platform_interface/lib/src/shared/opds/facet.dart

@@ -6,6 +6,7 @@ import 'package:dartx/dartx.dart';
 import 'package:equatable/equatable.dart';
 import 'package:meta/meta.dart';
 
+import '../../utils/constants.dart';
 import '../../utils/jsonable.dart';
 import '../opds.dart' show OpdsMetadata;
 import '../publication/link.dart' show Link;
@@ -23,8 +24,13 @@ class Facet with Equatable implements JSONable {
   @override
   String toString() => 'Facet{metadata: $metadata, links: $links}';
 
-  Facet copyWith({OpdsMetadata? metadata, List<Link>? links}) =>
-      Facet(metadata: metadata ?? this.metadata, links: links ?? this.links);
+  Facet copyWith({
+    Object? metadata = unset,
+    Object? links = unset,
+  }) => Facet(
+    metadata: identical(metadata, unset) ? this.metadata : (metadata as OpdsMetadata),
+    links: identical(links, unset) ? this.links : (links as List<Link>),
+  );
 
   @override
   Map<String, dynamic> toJson() {

flutter_readium_platform_interface/lib/src/shared/opds/feed.dart

@@ -50,27 +50,25 @@ class Feed extends AdditionalProperties with Equatable implements JSONable {
       'context: $context}';
 
   Feed copyWith({
-    OpdsMetadata? metadata,
-    List<Link>? links,
-    List<Facet>? facets,
-    List<Group>? groups,
-    List<OpdsPublication>? publications,
-    List<Link>? navigation,
-    List<String>? context,
-    Map<String, dynamic>? additionalProperties,
+    Object? metadata = unset,
+    Object? links = unset,
+    Object? facets = unset,
+    Object? groups = unset,
+    Object? publications = unset,
+    Object? navigation = unset,
+    Object? context = unset,
+    Object? additionalProperties = unset,
   }) {
-    final mergeProperties = Map<String, dynamic>.of(this.additionalProperties)
-      ..addAll(additionalProperties ?? {})
-      ..removeWhere((key, value) => value == null);
+    final mergeProperties = copyAdditionalProperties(additionalProperties: additionalProperties);
 
     return Feed(
-      metadata: metadata ?? this.metadata,
-      links: links ?? this.links,
-      facets: facets ?? this.facets,
-      groups: groups ?? this.groups,
-      publications: publications ?? this.publications,
-      navigation: navigation ?? this.navigation,
-      context: context ?? this.context,
+      metadata: identical(metadata, unset) ? this.metadata : (metadata as OpdsMetadata?)!,
+      links: identical(links, unset) ? this.links : (links as List<Link>?)!,
+      facets: identical(facets, unset) ? this.facets : (facets as List<Facet>?)!,
+      groups: identical(groups, unset) ? this.groups : (groups as List<Group>?)!,
+      publications: identical(publications, unset) ? this.publications : (publications as List<OpdsPublication>?)!,
+      navigation: identical(navigation, unset) ? this.navigation : (navigation as List<Link>?)!,
+      context: identical(context, unset) ? this.context : (context as List<String>?)!,
       additionalProperties: mergeProperties,
     );
   }

flutter_readium_platform_interface/lib/src/shared/opds/group.dart

@@ -7,6 +7,7 @@
 import 'package:equatable/equatable.dart';
 import 'package:meta/meta.dart';
 
+import '../../utils/constants.dart';
 import '../../utils/jsonable.dart';
 import '../opds.dart';
 import '../publication/link.dart';
@@ -34,15 +35,15 @@ class Group with Equatable implements JSONable {
       'publications: $publications, navigation: $navigation}';
 
   Group copyWith({
-    OpdsMetadata? metadata,
-    List<Link>? links,
-    List<OpdsPublication>? publications,
-    List<Link>? navigation,
+    Object? metadata = unset,
+    Object? links = unset,
+    Object? publications = unset,
+    Object? navigation = unset,
   }) => Group(
-    metadata: metadata ?? this.metadata,
-    links: links ?? this.links,
-    publications: publications ?? this.publications,
-    navigation: navigation ?? this.navigation,
+    metadata: identical(metadata, unset) ? this.metadata : (metadata as OpdsMetadata?)!,
+    links: identical(links, unset) ? this.links : (links as List<Link>?)!,
+    publications: identical(publications, unset) ? this.publications : (publications as List<OpdsPublication>?)!,
+    navigation: identical(navigation, unset) ? this.navigation : (navigation as List<Link>?)!,
   );
 
   @override