[rfw] Fix fontWeight not applied in release mode

FontWeight is not a real Dart enum; it is a hand-crafted class with
static const members. The previous implementation decoded fontWeight via
enumValue(), which matched strings against FontWeight.value.toString().
In AOT/release builds this is not guaranteed to be stable, so matches
silently failed and fontWeight defaulted to null (rendered as w400).

Add a dedicated ArgumentDecoders.fontWeight() method that maps strings
("w100"-"w900", "normal", "bold") and integers (100-900) to the correct
FontWeight constant using an explicit switch, without relying on
toString(). Update textStyle and strutStyle to use it.

Also fix three pre-existing bugs where absolute keys were used instead
of relative keys: textDirection in the sweep shader decoder, textBaseline
and overflow in textStyle.

Fixes flutter/flutter#180223

Made-with: Cursor

Author: iam-abhijha

packages/rfw/lib/src/flutter/argument_decoders.dart

@@ -632,6 +632,46 @@ class ArgumentDecoders {
     return null;
   }
 
+  /// Returns a [FontWeight] from the specified string or integer.
+  ///
+  /// This does not use [FontWeight.toString], which is not guaranteed to be
+  /// stable in release builds (since [FontWeight] is not a real Dart enum).
+  ///
+  /// Supported string values: `"w100"` through `"w900"`, `"normal"` (mapped to
+  /// [FontWeight.w400]), and `"bold"` (mapped to [FontWeight.w700]).
+  ///
+  /// Supported integer values: `100` through `900` in increments of 100.
+  static FontWeight? fontWeight(DataSource source, List<Object> key) {
+    final int? numeric = source.v<int>(key);
+    if (numeric != null) {
+      switch (numeric) {
+        case 100: return FontWeight.w100;
+        case 200: return FontWeight.w200;
+        case 300: return FontWeight.w300;
+        case 400: return FontWeight.w400;
+        case 500: return FontWeight.w500;
+        case 600: return FontWeight.w600;
+        case 700: return FontWeight.w700;
+        case 800: return FontWeight.w800;
+        case 900: return FontWeight.w900;
+      }
+    }
+    switch (source.v<String>(key)) {
+      case 'w100': return FontWeight.w100;
+      case 'w200': return FontWeight.w200;
+      case 'w300': return FontWeight.w300;
+      case 'w400':
+      case 'normal': return FontWeight.w400;
+      case 'w500': return FontWeight.w500;
+      case 'w600': return FontWeight.w600;
+      case 'w700':
+      case 'bold': return FontWeight.w700;
+      case 'w800': return FontWeight.w800;
+      case 'w900': return FontWeight.w900;
+    }
+    return null;
+  }
+
   /// Returns a [FontFeature] from the specified map.
   ///
   /// The `feature` key is used as the font feature name (defaulting to the
@@ -1243,7 +1283,7 @@ class ArgumentDecoders {
       case 'sweep':
         return gradient(source, key)!.createShader(
           rect(source, [...key, 'rect']) ?? Rect.zero,
-          textDirection: enumValue<TextDirection>(TextDirection.values, source, ['textDirection']) ?? TextDirection.ltr,
+          textDirection: enumValue<TextDirection>(TextDirection.values, source, [...key, 'textDirection']) ?? TextDirection.ltr,
         );
       default:
         final ArgumentDecoder<Shader?>? decoder = shaderDecoders[type];
@@ -1276,7 +1316,7 @@ class ArgumentDecoders {
   /// following keys: 'fontFamily` (string), `fontFamilyFallback` ([list] of
   /// [string]), `fontSize` (double), `height` (double), `leadingDistribution`
   /// ([enumValue] of [TextLeadingDistribution]), `leading` (double),
-  /// `fontWeight` ([enumValue] of [FontWeight]), `fontStyle` ([enumValue] of
+  /// `fontWeight` ([fontWeight]), `fontStyle` ([enumValue] of
   /// [FontStyle]), `forceStrutHeight` (boolean).
   static StrutStyle? strutStyle(DataSource source, List<Object> key) {
     if (!source.isMap(key)) {
@@ -1289,7 +1329,7 @@ class ArgumentDecoders {
       height: source.v<double>([...key, 'height']),
       leadingDistribution: enumValue<TextLeadingDistribution>(TextLeadingDistribution.values, source, [...key, 'leadingDistribution']),
       leading: source.v<double>([...key, 'leading']),
-      fontWeight: enumValue<FontWeight>(FontWeight.values, source, [...key, 'fontWeight']),
+      fontWeight: fontWeight(source, [...key, 'fontWeight']),
       fontStyle: enumValue<FontStyle>(FontStyle.values, source, [...key, 'fontStyle']),
       forceStrutHeight: source.v<bool>([...key, 'forceStrutHeight']),
     );
@@ -1350,7 +1390,7 @@ class ArgumentDecoders {
   ///
   /// Otherwise (even if it has no keys), the [TextStyle] is created from the
   /// following keys: `color` ([color]), `backgroundColor` ([color]), `fontSize`
-  /// (double), `fontWeight` ([enumValue] of [FontWeight]), `fontStyle`
+  /// (double), `fontWeight` ([fontWeight]), `fontStyle`
   /// ([enumValue] of [FontStyle]), `letterSpacing` (double), `wordSpacing`
   /// (double), `textBaseline` ([enumValue] of [TextBaseline]), `height`
   /// (double), `leadingDistribution` ([enumValue] of
@@ -1369,11 +1409,11 @@ class ArgumentDecoders {
       color: color(source, [...key, 'color']),
       backgroundColor: color(source, [...key, 'backgroundColor']),
       fontSize: source.v<double>([...key, 'fontSize']),
-      fontWeight: enumValue<FontWeight>(FontWeight.values, source, [...key, 'fontWeight']),
+      fontWeight: fontWeight(source, [...key, 'fontWeight']),
       fontStyle: enumValue<FontStyle>(FontStyle.values, source, [...key, 'fontStyle']),
       letterSpacing: source.v<double>([...key, 'letterSpacing']),
       wordSpacing: source.v<double>([...key, 'wordSpacing']),
-      textBaseline: enumValue<TextBaseline>(TextBaseline.values, source, ['textBaseline']),
+      textBaseline: enumValue<TextBaseline>(TextBaseline.values, source, [...key, 'textBaseline']),
       height: source.v<double>([...key, 'height']),
       leadingDistribution: enumValue<TextLeadingDistribution>(TextLeadingDistribution.values, source, [...key, 'leadingDistribution']),
       locale: locale(source, [...key, 'locale']),
@@ -1387,7 +1427,7 @@ class ArgumentDecoders {
       decorationThickness: source.v<double>([...key, 'decorationThickness']),
       fontFamily: source.v<String>([...key, 'fontFamily']),
       fontFamilyFallback: list<String>(source, [...key, 'fontFamilyFallback'], string),
-      overflow: enumValue<TextOverflow>(TextOverflow.values, source, ['overflow']),
+      overflow: enumValue<TextOverflow>(TextOverflow.values, source, [...key, 'overflow']),
     );
   }
 

packages/rfw/test/argument_decoders_test.dart

@@ -187,6 +187,19 @@ void main() {
     await tester.pump();
     expect(tester.widget<Directionality>(find.byType(Directionality)).textDirection, TextDirection.ltr);
 
+    runtime.update(const LibraryName(<String>['test']), parseLibraryFile('''
+      import core;
+      widget root = Directionality(
+        textDirection: "ltr",
+        child: Text(
+          text: 'Hello',
+          style: { fontWeight: "w700" },
+        ),
+      );
+    '''));
+    await tester.pump();
+    expect(tester.widget<Text>(find.byType(Text)).style!.fontWeight, FontWeight.w700);
+
     runtime.update(const LibraryName(<String>['test']), parseLibraryFile('''
       import core;
       widget root = FittedBox(