Update Dart duration serialization to be compatible with Kotlin ISO-8…

…601 duration string parsing

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## unreleased
 
 - Fix conflicts with same method names across different modules on iOS by prefixing method names
+- Update Dart duration serialization to be compatible with Kotlin ISO-8601 duration string parsing
 
 ## v0.1.0-rc.2
 

example/flutter/example/lib/main.dart

@@ -139,6 +139,7 @@ class _MyAppState extends State<MyApp> {
     print(await myTestModule.localDateMethod(DateTime.now()));
     print(await myTestModule.localTimeMethod(TimeOfDay.now()));
     print(await myTestModule.durationMethod(const Duration(seconds: 123)));
+    print(await myTestModule.durationMethod(const Duration(days: 1000)));
 
     print(await myTestModule.dateClassMethod(MyDateClass(
         DateTime.now(),
@@ -147,6 +148,13 @@ class _MyAppState extends State<MyApp> {
         const Duration(seconds: 123),
         DateTime.now().toUtc())));
 
+    print(await myTestModule.dateClassMethod(MyDateClass(
+        DateTime.now(),
+        TimeOfDay.now(),
+        DateTime.now(),
+        const Duration(days: 1000),
+        DateTime.now().toUtc())));
+
     final broadcaster = myTestModule.intEvents;
 
     // this starts a collect on the counter flow that is shared across all listeners

example/flutter/lib/MyTestModule.dart

@@ -349,7 +349,16 @@ final localDateSerialized = localDate.toIso8601String().split('T').first;
     return result;
 }
 Future<Duration> durationMethod(Duration duration) async {
-    final durationSerialized = duration.toIso8601String();
+    final durationSerialized = duration.toIso8601String().replaceFirstMapped(RegExp(r'P([^T]*)(T.*)?'), (m) {
+        int totalDays = 0;
+        String datePart = m[1]!
+          .replaceAllMapped(RegExp(r'(\d+)Y'), (y) { totalDays += int.parse(y[1]!) * 365; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)M'), (m) { totalDays += int.parse(m[1]!) * 30; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)W'), (w) { totalDays += int.parse(w[1]!) * 7; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)D'), (d) { totalDays += int.parse(d[1]!); return ''; });
+
+        return 'P' + (totalDays > 0 ? '${totalDays}D' : '') + (m[2] ?? '');
+    });
     final invokeResult = await methodChannelToNative.invokeMethod<String>(
         'MyTestModule_durationMethod',
         [durationSerialized],

example/flutter/lib/models.dart

@@ -85,7 +85,16 @@ MyDateClass(this.date, this.time, this.dateTime, this.duration, this.instant);
         static TimeOfDay _timeFromJson(String json) => TimeOfDay.fromDateTime(DateTime.parse("1998-01-01T$json:00.000"));
 
 
-        static String _durationToJson(Duration obj) => obj.toIso8601String();
+        static String _durationToJson(Duration obj) => obj.toIso8601String().replaceFirstMapped(RegExp(r'P([^T]*)(T.*)?'), (m) {
+        int totalDays = 0;
+        String datePart = m[1]!
+          .replaceAllMapped(RegExp(r'(\d+)Y'), (y) { totalDays += int.parse(y[1]!) * 365; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)M'), (m) { totalDays += int.parse(m[1]!) * 30; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)W'), (w) { totalDays += int.parse(w[1]!) * 7; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)D'), (d) { totalDays += int.parse(d[1]!); return ''; });
+
+        return 'P' + (totalDays > 0 ? '${totalDays}D' : '') + (m[2] ?? '');
+    });
         static Duration _durationFromJson(String json) => parseIso8601Duration(json);
 
 

flutter-kmp-ksp/src/main/kotlin/de/voize/flutterkmp/ksp/processor/DartGenerator.kt

@@ -520,7 +520,7 @@ ${declaration.declarations.filterIsInstance<KSClassDeclaration>()
         val serializedType: String,
     )
 
-    val customSerializations = listOf(
+    private val customSerializations = listOf(
         // TimeOfDay is part of the material package and is not serializable by default
         CustomSerialization(
             detect = { prop ->
@@ -548,7 +548,7 @@ ${declaration.declarations.filterIsInstance<KSClassDeclaration>()
                     this.toDartType() is DartType.Duration
                 }
             },
-            serializeFnString = { varName, _ -> "$varName.toIso8601String()" },
+            serializeFnString = { varName, _ -> "$varName.toIso8601String().$patchIso8601DurationStringDartCode" },
             deserializeFnString = { varName, _ -> "parseIso8601Duration($varName)" },
             serializedType = "String",
         ),

flutter-kmp-ksp/src/main/kotlin/de/voize/flutterkmp/ksp/processor/utils.kt

@@ -346,7 +346,7 @@ internal fun DartType.getDartSerializationStatement(varName: String): String? {
             is DartType.Primitive.Int,
             is DartType.Primitive.String -> return null
         }
-        is DartType.Duration -> "${varName}.toIso8601String()"
+        is DartType.Duration -> "${varName}.toIso8601String().$patchIso8601DurationStringDartCode"
         is DartType.TimeOfDay -> "\"${'$'}{$varName.hour.toString().padLeft(2, '0')}:${'$'}{$varName.minute.toString().padLeft(2, '0')}\""
         is DartType.LocalDate -> "${varName}.toIso8601String().split('T').first"
         is DartType.DateTime, is DartType.LocalDateTime -> "$varName.toIso8601String()"
@@ -362,4 +362,23 @@ internal fun DartType.getDartSerializationStatement(varName: String): String? {
         is DartType.List -> "jsonEncode(${transformEnumsForSerialization(varName, this)})"
         is DartType.Map -> "jsonEncode(${transformEnumsForSerialization(varName, this)})"
     } + ";"
-}
+}
+
+/**
+ * The Pub package we use to parse Dart Durations to ISO-8601 strings, [iso_duration](https://github.com/pti/iso_duration),
+ * uses W, M, Y for day designators, which are not supported in kotlin.time.Duration ISO-8601 string parsing,
+ * see [here](https://kotlinlang.org/api/core/kotlin-stdlib/kotlin.time/-duration/-companion/parse-iso-string.html).
+ *
+ * This code runs as an extension on a "x.toIso8601String()" call to patch
+ * the ISO-8601 duration string to use D instead of W, M, Y with W=7D, M=30D, Y=365D.
+ */
+internal const val patchIso8601DurationStringDartCode = """replaceFirstMapped(RegExp(r'P([^T]*)(T.*)?'), (m) {
+        int totalDays = 0;
+        String datePart = m[1]!
+          .replaceAllMapped(RegExp(r'(\d+)Y'), (y) { totalDays += int.parse(y[1]!) * 365; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)M'), (m) { totalDays += int.parse(m[1]!) * 30; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)W'), (w) { totalDays += int.parse(w[1]!) * 7; return ''; })
+          .replaceAllMapped(RegExp(r'(\d+)D'), (d) { totalDays += int.parse(d[1]!); return ''; });
+
+        return 'P' + (totalDays > 0 ? '${"$"}{totalDays}D' : '') + (m[2] ?? '');
+    })"""