Fix FwfhTextStyle usage within CupertinoPageScaffold

.github/workflows/backward_compatibility.yml

@@ -75,6 +75,11 @@ jobs:
           flutter-version: ${{ env.FLUTTER_VERSION }}
 
       - run: flutter test
+      - uses: actions/upload-artifact@v2
+        if: failure()
+        with:
+          name: failures
+          path: packages/${{ matrix.package }}/test/failures/
 
   fwfh_text_style:
     strategy:
@@ -109,3 +114,8 @@ jobs:
           channel: ${{ matrix.channel }}
       - run: flutter --version
       - run: flutter test
+      - uses: actions/upload-artifact@v2
+        if: failure()
+        with:
+          name: failures
+          path: packages/fwfh_text_style/test/failures/

packages/core/lib/src/data/text_style.dart

@@ -57,12 +57,6 @@ class TextStyleHtml {
     TextDirection? textDirection,
     CssWhitespace? whitespace,
   }) {
-    assert(
-      style is FwfhTextStyle?,
-      'The text style should be modified by methods of the existing instance: '
-      'apply(), copyWith() or merge().',
-    );
-
     return TextStyleHtml._(
       deps: _deps,
       parent: parent ?? this.parent,

packages/core/test/core_test.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter_widget_from_html_core/flutter_widget_from_html_core.dart';
@@ -1585,6 +1586,22 @@ Future<void> main() async {
       });
     });
   });
+
+  testWidgets('#698: MaterialApp > CupertinoPageScaffold', (tester) async {
+    const html = 'Hello world';
+    final key = GlobalKey<HtmlWidgetState>();
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: CupertinoPageScaffold(
+          child: HtmlWidget(html, key: key),
+        ),
+      ),
+    );
+
+    final explained = await explainWithoutPumping(key: key);
+    expect(explained, equals('[RichText:(#D0FF0000:$html)]'));
+  });
 }
 
 class _InlineBlockOnWidgetsFactory extends WidgetFactory {

packages/fwfh_text_style/lib/fwfh_text_style.dart

@@ -7,16 +7,33 @@ const _default = _DefaultValue();
 
 /// A [TextStyle] replacement.
 class FwfhTextStyle extends _TextStyleProxy {
-  /// Creates an instance from a [TextStyle] with inherit=false.
+  /// Creates an instance from another [TextStyle].
   ///
   /// See also: [FwfhTextStyle.of].
-  FwfhTextStyle.from(TextStyle ref)
-      : super._(ref is FwfhTextStyle ? ref.ref : ref);
+  static TextStyle from(TextStyle ref) {
+    if (ref.inherit) {
+      debugPrint(
+        'Warning: Text style instance #${ref.hashCode} has inherit=true, '
+        'resetting its height will not be supported.',
+      );
+      assert(
+        () {
+          debugPrint(StackTrace.current.toString());
+          return true;
+        }(),
+      );
+      return ref;
+    } else {
+      return FwfhTextStyle._(ref is FwfhTextStyle ? ref.ref : ref);
+    }
+  }
 
   /// Creates an instance from the closest [DefaultTextStyle].
-  factory FwfhTextStyle.of(BuildContext context) =>
+  static TextStyle of(BuildContext context) =>
       FwfhTextStyle.from(DefaultTextStyle.of(context).style);
 
+  FwfhTextStyle._(TextStyle ref) : super._(ref);
+
   @override
   TextStyle apply({
     Color? color,
@@ -163,12 +180,7 @@ class _DefaultValue {
 abstract class _TextStyleProxy implements TextStyle {
   final TextStyle ref;
 
-  _TextStyleProxy._(this.ref)
-      : assert(
-          ref.inherit == false,
-          "FwfhTextStyle.from() doesn't support incomplete TextStyle. "
-          'Use `DefaultTextStyle.of(context)` to obtain the current style.',
-        );
+  _TextStyleProxy._(this.ref);
 
   @override
   Paint? get background => ref.background;
@@ -279,8 +291,11 @@ abstract class _TextStyleProxy implements TextStyle {
   @override
   double? get height => ref.height;
 
+  /// Flutter's [TextStyle.merge] implementation uses private properties
+  /// which will trigger weird errors in people's apps.
+  /// We cannot let that happen.
   @override
-  bool get inherit => ref.inherit;
+  bool get inherit => false;
 
   @override
   TextLeadingDistribution? get leadingDistribution => ref.leadingDistribution;

packages/fwfh_text_style/test/fwfh_text_style_test.dart

@@ -1,5 +1,6 @@
 import 'dart:io';
 
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:fwfh_text_style/fwfh_text_style.dart';
@@ -120,6 +121,7 @@ Future<void> main() async {
       });
 
       test('resets to null', () {
+        // ignore: avoid_redundant_argument_values
         final copied = obj.copyWith(height: null);
         expect(copied.height, isNull);
         expect(copied, isNot(equals(obj)));
@@ -264,6 +266,27 @@ Future<void> main() async {
 
             await screenMatchesGolden(tester, 'TextSpan');
           });
+
+          testGoldens(
+            '#698: MaterialApp > CupertinoPageScaffold',
+            (tester) async {
+              await tester.pumpWidget(
+                MaterialApp(
+                  home: CupertinoPageScaffold(
+                    child: Builder(
+                      builder: (context) => Text(
+                        'Foo Roboto',
+                        style: FwfhTextStyle.of(context)
+                            .copyWith(fontFamily: 'Roboto'),
+                      ),
+                    ),
+                  ),
+                ),
+              );
+
+              await screenMatchesGolden(tester, 'CupertinoPageScaffold');
+            },
+          );
         },
         skip: goldenSkip,
       );