feat: add support for underline attribute with strict encoding parameter

packages/fleather/lib/fleather.dart

@@ -14,7 +14,6 @@ export 'src/widgets/cursor.dart';
 export 'src/widgets/editor.dart';
 export 'src/widgets/editor_toolbar.dart';
 export 'src/widgets/field.dart';
-export 'src/widgets/fleather_localizations.dart';
 export 'src/widgets/link.dart' show LinkActionPickerDelegate, LinkMenuAction;
 export 'src/widgets/text_line.dart';
 export 'src/widgets/theme.dart';

packages/parchment/lib/src/codecs/markdown.dart

@@ -1,23 +1,25 @@
 import 'dart:convert';
 
-import 'package:parchment_delta/parchment_delta.dart';
-
-import '../document.dart';
-import '../document/attributes.dart';
-import '../document/block.dart';
-import '../document/leaf.dart';
-import '../document/line.dart';
+import 'package:parchment/parchment.dart';
 
 class ParchmentMarkdownCodec extends Codec<ParchmentDocument, String> {
-  const ParchmentMarkdownCodec();
+  const ParchmentMarkdownCodec({this.strictEncoding = true});
+
+  /// Whether to strictly stick to the Markdown syntax during the encoding.
+  ///
+  /// If this option is enabled, during the encoding, if attributes that are
+  /// not natively supported by the Markdown syntax exist, an exception will be
+  /// thrown. Otherwise, they will be converted in the best way possible
+  /// (for example with HTML tags, plain text or placeholders).
+  final bool strictEncoding;
 
   @override
   Converter<String, ParchmentDocument> get decoder =>
       _ParchmentMarkdownDecoder();
 
   @override
   Converter<ParchmentDocument, String> get encoder =>
-      _ParchmentMarkdownEncoder();
+      _ParchmentMarkdownEncoder(strict: strictEncoding);
 }
 
 class _ParchmentMarkdownDecoder extends Converter<String, ParchmentDocument> {
@@ -354,6 +356,10 @@ class _ParchmentMarkdownDecoder extends Converter<String, ParchmentDocument> {
 }
 
 class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
+  const _ParchmentMarkdownEncoder({required this.strict});
+
+  final bool strict;
+
   static final simpleBlocks = <ParchmentAttribute, String>{
     ParchmentAttribute.bq: '> ',
     ParchmentAttribute.ul: '* ',
@@ -403,8 +409,6 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
     ParchmentAttribute? currentBlockAttribute;
 
     void handleLine(LineNode node) {
-      if (node.hasBlockEmbed) return;
-
       for (final attr in node.style.lineAttributes) {
         if (attr.key == ParchmentAttribute.block.key) {
           if (currentBlockAttribute != attr) {
@@ -486,8 +490,11 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
     return buffer.toString();
   }
 
-  void _writeAttribute(StringBuffer buffer, ParchmentAttribute? attribute,
-      {bool close = false}) {
+  void _writeAttribute(
+    StringBuffer buffer,
+    ParchmentAttribute? attribute, {
+    bool close = false,
+  }) {
     if (attribute == ParchmentAttribute.bold) {
       _writeBoldTag(buffer);
     } else if (attribute == ParchmentAttribute.italic) {
@@ -497,18 +504,26 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
     } else if (attribute == ParchmentAttribute.strikethrough) {
       _writeStrikeThoughTag(buffer);
     } else if (attribute?.key == ParchmentAttribute.link.key) {
-      _writeLinkTag(buffer, attribute as ParchmentAttribute<String>,
-          close: close);
+      _writeLinkTag(
+        buffer,
+        attribute as ParchmentAttribute<String>,
+        close: close,
+      );
     } else if (attribute?.key == ParchmentAttribute.heading.key) {
       _writeHeadingTag(buffer, attribute as ParchmentAttribute<int>);
     } else if (attribute?.key == ParchmentAttribute.block.key) {
-      _writeBlockTag(buffer, attribute as ParchmentAttribute<String>,
-          close: close);
+      _writeBlockTag(
+        buffer,
+        attribute as ParchmentAttribute<String>,
+        close: close,
+      );
     } else if (attribute?.key == ParchmentAttribute.checked.key) {
       // no-op already handled in handleBlock
     } else if (attribute?.key == ParchmentAttribute.indent.key) {
       // no-op already handled in handleBlock
-    } else {
+    } else if (!strict && attribute?.key == ParchmentAttribute.underline.key) {
+      _writeUnderlineTag(buffer, close: close);
+    } else if (strict) {
       throw ArgumentError('Cannot handle $attribute');
     }
   }
@@ -521,6 +536,14 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
     buffer.write('_');
   }
 
+  void _writeUnderlineTag(StringBuffer buffer, {bool close = false}) {
+    if (false) {
+      buffer.write('</u>');
+    } else {
+      buffer.write('<u>');
+    }
+  }
+
   void _writeInlineCodeTag(StringBuffer buffer) {
     buffer.write('`');
   }
@@ -529,8 +552,11 @@ class _ParchmentMarkdownEncoder extends Converter<ParchmentDocument, String> {
     buffer.write('~~');
   }
 
-  void _writeLinkTag(StringBuffer buffer, ParchmentAttribute<String> link,
-      {bool close = false}) {
+  void _writeLinkTag(
+    StringBuffer buffer,
+    ParchmentAttribute<String> link, {
+    bool close = false,
+  }) {
     if (close) {
       buffer.write('](${link.value})');
     } else {

packages/parchment/lib/src/document/line.dart

@@ -26,6 +26,12 @@ final class LineNode extends ContainerNode<LeafNode> with StyledNode {
     return false;
   }
 
+  EmbedNode get embedNode {
+    assert(hasBlockEmbed);
+
+    return children.single as EmbedNode;
+  }
+
   /// Returns next [LineNode] or `null` if this is the last line in the document.
   LineNode? get nextLine {
     if (isLast) {