🦺 add strict list limit checks for empty root input in decode tests

Author: techouse

lib/src/extensions/decode.dart

@@ -405,10 +405,13 @@ extension _$Decode on QS {
     DecodeOptions options,
     bool valuesParsed,
   ) {
+    final bool isListGrowthPath =
+        chain.isNotEmpty && chain.last == '[]' && options.parseLists;
+
     // Determine the current list length if we are appending into `[]`.
     late final int currentListLength;
 
-    if (chain.length >= 2 && chain.last == '[]') {
+    if (isListGrowthPath && chain.length >= 2) {
       final String prev = chain[chain.length - 2];
       final bool bracketed = prev.startsWith('[') && prev.endsWith(']');
       final int? parentIndex =
@@ -433,7 +436,7 @@ extension _$Decode on QS {
             val,
             options,
             currentListLength,
-            chain.length >= 2 && chain.last == '[]' && options.parseLists,
+            isListGrowthPath,
           );
 
     for (int i = chain.length - 1; i >= 0; --i) {

test/unit/decode_test.dart

@@ -2113,6 +2113,38 @@ void main() {
   });
 
   group('list limit tests', () {
+    test('map input root [] enforces strict list limit checks', () {
+      expect(
+        () => QS.decode(
+          {'[]': 'a'},
+          const DecodeOptions(listLimit: 0, throwOnLimitExceeded: true),
+        ),
+        throwsA(
+          isA<RangeError>().having(
+            (e) => e.message,
+            'message',
+            contains('List limit exceeded'),
+          ),
+        ),
+      );
+    });
+
+    test('map input root [] enforces negative listLimit strict mode', () {
+      expect(
+        () => QS.decode(
+          {'[]': 'a'},
+          const DecodeOptions(listLimit: -1, throwOnLimitExceeded: true),
+        ),
+        throwsA(
+          isA<RangeError>().having(
+            (e) => e.message,
+            'message',
+            contains('List parsing is disabled'),
+          ),
+        ),
+      );
+    });
+
     test('strict list limit applies when duplicate scalar grows into a list',
         () {
       expect(