Add ISSUE-6312 search markers

Author: EricFeng9

sdk/python/packages/flet-code-editor/src/flutter/flet_code_editor/lib/src/utils/flet_code_controller.dart

@@ -5,12 +5,16 @@ import 'package:highlight/languages/json.dart';
 import 'json_analyzer.dart';
 
 class FletCodeController extends fce.CodeController {
+  // ISSUE-6312: Use a dedicated analyzer for JSON so invalid JSON can surface
+  // gutter markers instead of falling back to the default fold-only analyzer.
   FletCodeController({super.text, super.language})
     : super(analyzer: _analyzerForLanguage(language));
 
   bool autocompletionEnabled = false;
 
   static fce.AbstractAnalyzer _analyzerForLanguage(dynamic language) {
+    // ISSUE-6312: Keep existing behavior for other languages and only switch
+    // JSON to the custom analyzer added for this bug fix.
     return language != json
         ? const fce.DefaultLocalAnalyzer()
         : const JsonLocalAnalyzer();

sdk/python/packages/flet-code-editor/src/flutter/flet_code_editor/lib/src/utils/json_analyzer.dart

@@ -2,6 +2,8 @@ import 'dart:convert';
 
 import 'package:flutter_code_editor/flutter_code_editor.dart' as fce;
 
+// ISSUE-6312: JSON syntax errors were not converted into editor issues, so the
+// gutter had nothing to render. This analyzer adds real JSON validation.
 class JsonLocalAnalyzer extends fce.AbstractAnalyzer {
   const JsonLocalAnalyzer();
 
@@ -18,6 +20,7 @@ class JsonLocalAnalyzer extends fce.AbstractAnalyzer {
     try {
       jsonDecode(code.text);
     } on FormatException catch (error) {
+      // ISSUE-6312: Translate JSON parsing failures into gutter-visible issues.
       issues.add(
         fce.Issue(
           line: _lineFromOffset(code.text, error.offset),
@@ -31,6 +34,8 @@ class JsonLocalAnalyzer extends fce.AbstractAnalyzer {
   }
 
   int _lineFromOffset(String text, int? offset) {
+    // ISSUE-6312: Map the parser offset back to a line number for gutter
+    // rendering.
     final safeOffset = (offset ?? 0).clamp(0, text.length);
     return '\n'.allMatches(text.substring(0, safeOffset)).length;
   }

sdk/python/packages/flet-code-editor/src/flutter/flet_code_editor/test/json_gutter_analyzer_test.dart

@@ -6,6 +6,7 @@ import 'package:flet_code_editor/src/utils/flet_code_controller.dart';
 import 'package:flet_code_editor/src/utils/json_analyzer.dart';
 
 void main() {
+  // ISSUE-6312: Regression coverage for missing JSON gutter error markers.
   group('FletCodeController JSON analyzer', () {
     test('uses JSON analyzer for JSON language', () {
       final controller = FletCodeController(