Checklist: Maintain the case of 'x'

lib/core/checklist.dart

@@ -190,6 +190,8 @@ class TaskListSyntax extends md.InlineSyntax {
     var m = match[1].trim();
     if (m.isNotEmpty) {
       el.attributes['xUpperCase'] = (m[0] == 'X').toString();
+    } else {
+      el.attributes['xUpperCase'] = "false";
     }
     el.attributes['text'] = '${match[2]}';
     parser.addNode(el);
@@ -259,12 +261,13 @@ class CustomRenderer implements md.NodeVisitor {
     if (tag == 'input') {
       var el = element;
       if (el is md.Element && el.attributes['type'] == 'checkbox') {
+        assert(el.attributes.containsKey('xUpperCase'));
         bool val = el.attributes['checked'] != 'false';
         if (val) {
           if (el.attributes['xUpperCase'] != 'false') {
-            buffer.write('[x] ');
-          } else {
             buffer.write('[X] ');
+          } else {
+            buffer.write('[x] ');
           }
         } else {
           buffer.write('[ ] ');

test/checklist_test.dart

@@ -94,7 +94,7 @@ How are you doing?
 
 [x] item 1
 [ ] Foo
-[X] item 3
+[x] item 3
 [ ] item 4
 
 Booga Wooga
@@ -226,5 +226,21 @@ Booga Wooga
       note = checklist.note;
       expect(note.body, "[ ] One\n[ ]Two\n[ ] Three\n[ ] Four\n[ ] Five\n");
     });
+
+    test('Maintain x case', () async {
+      var content = "[X] One\n[ ]Two";
+
+      var notePath = p.join(tempDir.path, "note448.md");
+      await File(notePath).writeAsString(content);
+
+      var parentFolder = NotesFolderFS(null, tempDir.path);
+      var note = Note(parentFolder, notePath);
+      await note.load();
+
+      var checklist = Checklist(note);
+
+      note = checklist.note;
+      expect(note.body, content);
+    });
   });
 }