fix: changing heading from one level to another from toolbar

lib/src/core/document/attributes.dart

@@ -1,8 +1,14 @@
+import 'package:flutter/foundation.dart';
+
 /// Attributes is used to describe the Node's information.
 ///
 /// Please note: The keywords in [BuiltInAttributeKey] are reserved.
 typedef Attributes = Map<String, dynamic>;
 
+bool isAttributesEqual(Attributes? a, Attributes? b) {
+  return mapEquals(a, b);
+}
+
 Attributes? composeAttributes(
   Attributes? base,
   Attributes? other, {

lib/src/service/default_text_operations/format_rich_text_style.dart

@@ -108,21 +108,21 @@ bool formatTextNodes(EditorState editorState, Attributes attributes) {
 
   for (final textNode in textNodes) {
     var newAttributes = {...textNode.attributes};
-    for (final globalStyleKey in BuiltInAttributeKey.globalStyleKeys) {
-      if (newAttributes.keys.contains(globalStyleKey)) {
-        newAttributes[globalStyleKey] = null;
+    if (isAttributesEqual(newAttributes, attributes)) {
+      for (final key in attributes.keys) {
+        newAttributes[key] = null;
       }
-    }
-
-    // if an attribute already exists in the node, it should be removed instead
-    for (final entry in attributes.entries) {
-      if (textNode.attributes.containsKey(entry.key) &&
-          textNode.attributes[entry.key] == entry.value) {
-        // attribute is not added to the node new attributes
-      } else {
-        newAttributes.addEntries([entry]);
+    } else {
+      for (final globalStyleKey in BuiltInAttributeKey.globalStyleKeys) {
+        if (newAttributes.keys.contains(globalStyleKey)) {
+          newAttributes[globalStyleKey] = null;
+        }
       }
+
+      // if an attribute already exists in the node, it should be removed instead
+      newAttributes.addAll(attributes);
     }
+
     transaction
       ..updateNode(
         textNode,

test/service/default_text_operations/format_rich_text_style_test.dart

@@ -1,4 +1,5 @@
 import 'package:appflowy_editor/appflowy_editor.dart';
+import 'package:appflowy_editor/src/render/rich_text/heading_text.dart';
 import 'package:appflowy_editor/src/render/rich_text/quoted_text.dart';
 import 'package:flutter_test/flutter_test.dart';
 import '../../infra/test_editor.dart';
@@ -31,5 +32,36 @@ void main() async {
       await tester.pumpAndSettle();
       expect(find.byType(QuotedTextNodeWidget), findsNothing);
     });
+
+    testWidgets('formatHeading', (tester) async {
+      const text = 'Welcome to Appflowy 😁';
+      final editor = tester.editor
+        ..insertTextNode(
+          text,
+          attributes: {
+            BuiltInAttributeKey.subtype: BuiltInAttributeKey.heading,
+            BuiltInAttributeKey.heading: BuiltInAttributeKey.h2,
+          },
+        );
+      await editor.startTesting();
+      await editor.updateSelection(
+        Selection.single(path: [0], startOffset: 0, endOffset: text.length),
+      );
+
+      // format the text to h1
+      formatHeading(editor.editorState, BuiltInAttributeKey.h1);
+      await tester.pumpAndSettle(const Duration(milliseconds: 100));
+      expect(find.byType(HeadingTextNodeWidget), findsOneWidget);
+
+      final textNode = editor.nodeAtPath([0])!;
+      expect(
+        textNode.attributes[BuiltInAttributeKey.subtype],
+        BuiltInAttributeKey.heading,
+      );
+      expect(
+        textNode.attributes[BuiltInAttributeKey.heading],
+        BuiltInAttributeKey.h1,
+      );
+    });
   });
 }