[BUG] Nullable query or param annotated data types are not working.

[ShreemanMassTech]

🐛 Bug Report

Whenever a nullable parameter/query annotated with @query or @param , the generated swagger have wrong type for the paramter and generated coe not able to parse/handle the nullable case.

📄 Code

import 'package:vaden/vaden.dart';

@Api(tag: 'Fibo', description: 'FiboSeriesController')
@Controller("/fibo")
class FiboSeriesController {
  @Get('/fibonacci')
  Future<String> getFibonacciSeries(@Query('n') int? n) async {
    if (n == null) {
      return "Please provide a number";
    }
    List<int> fiboSeries = [0, 1];
    while (fiboSeries.last < n) {
      fiboSeries.add(
        fiboSeries.last + fiboSeries.last - fiboSeries[0],
      ); // This line is the key to the Fibonacci series
    }
    return fiboSeries.toString();
  }
}

✅ Expected Result

Nullable query parameter should check types accordingly return missing query or param paramters and return result.

[0, 1, 2, 4, 8, 16, 32, 64]

❌ Actual Result

Terminal Error

type 'String' is not a subtype of type 'int?' in type cast
#0      VadenApplicationImpl._parse (package:portfolio/vaden_application.dart:374:20)
#1      VadenApplicationImpl.setup.<anonymous closure> (package:portfolio/vaden_application.dart:216:17)
#2      RouterEntry.invoke.<anonymous closure> (package:shelf_router/src/router_entry.dart:107:30)
#3      RouterEntry.invoke (package:shelf_router/src/router_entry.dart:113:7)
#4      Router.call (package:shelf_router/src/router.dart:184:38)
#5      Router.mount.<anonymous closure> (package:shelf_router/src/router.dart:167:23)
#6      RouterEntry.invoke.<anonymous closure> (package:shelf_router/src/router_entry.dart:107:30)
#7      RouterEntry.invoke (package:shelf_router/src/router_entry.dart:113:7)
#8      Router.call (package:shelf_router/src/router.dart:184:38)
<asynchronous suspension>
#9      VadenApplicationImpl.run.<anonymous closure> (package:portfolio/vaden_application.dart:40:26)
<asynchronous suspension>
#10     CalculateTotalTimeMiddleware.handler (package:portfolio/config/app_configuration.dart:51:22)
<asynchronous suspension>
#11     logRequests.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:shelf/src/middleware/logger.dart:30:62)
<asynchronous suspension>
#12     EnforceJsonContentType.handler (package:vaden/src/middlewares/enforce_json_content_type.dart:48:22)
<asynchronous suspension>
#13     cors.<anonymous closure>.<anonymous closure> (package:vaden/src/middlewares/cors.dart:67:24)
<asynchronous suspension>
#14     handleRequest (package:shelf/shelf_io.dart:140:16)
<asynchronous suspension>

Total time taken: 13 ms
2025-05-05T22:44:42.774758  0:00:00.011944 GET     [500] /fibo/fibonacci?n=58

API Response

{
    "error": "Internal server error"
}

📷 Evidence

⚠️ Severity

• Low
• Medium
• High
• Critical

🚨 Priority

• P1 (High)
• P2 (Medium)
• P3 (Low)

[ShreemanMassTech]

i think exact cause due to _parse function. i modified which helps on more use case. @jacobaraujo7

typedef Nullable<T> = T?;

T? _parse<T extends Object?>(String? value) {
  if (value == null) {
    return null;
  }

  try {
    if (T == Nullable<int>) {
      return int.tryParse(value) as T?;
    } else if (T == Nullable<double>) {
      return double.tryParse(value) as T?;
    } else if (T == Nullable<bool>) {
      return bool.tryParse(value) as T?;
    } else if (T == Nullable<List>) {
      // Regex for empty list:  r'^\s*\[\s*\]\s*$'
      // Regex for filled list: r'^\s*\[\s*(.+?)\s*\]\s*$'
      if (RegExp(r'^\s*\[\s*\]\s*$').hasMatch(value)) {
        return <String>[] as T?; // Return an empty list of strings
      } else if (RegExp(r'^\s*\[\s*(.+?)\s*\]\s*$').hasMatch(value)) {
        final match = RegExp(r'^\s*\[\s*(.+?)\s*\]\s*$').firstMatch(value);
        final listContent = match?.group(1) ?? "";
        final stringList = listContent.split(',');
        return stringList.map((e) => e.trim()).toList() as T?;
      } else {
        return null; // Or throw an exception for invalid format
      }
    } else if (T == int) {
      return int.parse(value) as T?;
    } else if (T == double) {
      return double.parse(value) as T?;
    } else if (T == bool) {
      return value.toLowerCase() == "true"
          ? true as T?
          : (value.toLowerCase() == "false" ? false as T? : null);
    } else if (T == List) {
      if (RegExp(r'^\s*\[\s*\]\s*$').hasMatch(value)) {
        return <String>[] as T?;
      } else if (RegExp(r'^\s*\[\s*(.+?)\s*\]\s*$').hasMatch(value)) {
        final match = RegExp(r'^\s*\[\s*(.+?)\s*\]\s*$').firstMatch(value);
        final listContent = match?.group(1) ?? "";
        final stringList = listContent.split(',');
        return stringList.map((e) => e.trim()).toList() as T?;
      } else {
        return null; // Or throw an exception for invalid format
      }
    } else {
      return value as T?;
    }
  } catch (e) {
    return null;
  }
}

Test

import 'package:flutter_test/flutter_test.dart';


void main() {
  test(
    'parse nullable type',
    () {
      expect(_parse<int>('123'), 123);
      expect(_parse<int?>('123'), 123);
      expect(_parse<int?>(null), null);
      expect(_parse<double?>('123.456'), 123.456);
      expect(_parse<double?>(null), null);
      expect(_parse<bool?>('true'), true);
      expect(_parse<bool?>('false'), false);
      expect(_parse<bool?>('1'), null);
      expect(_parse<bool?>('0'), null);
      expect(_parse<bool?>('invalid'), null);
      expect(_parse<bool?>(null), null);
      expect(_parse<String?>('hello'), 'hello');
      expect(_parse<String?>(null), null);
      expect(_parse<List?>('[1,2,3]'), ['1', '2', '3']);
      expect(_parse<List?>('[a, b, c]'), ['a', 'b', 'c']);
      expect(_parse<List>('[]'), []); // Test for empty list
      expect(_parse<List?>('[]'), []);
      expect(_parse<List?>('[  ]'), []);
      expect(_parse<List?>('[ 1, 2, 3 ]'), ['1', '2', '3']);
      expect(_parse<List?>(null), null);
      expect(_parse<List?>('[1,2,3'), null); // Invalid format
      expect(_parse<List?>('1,2,3]'), null); // Invalid format
      expect(_parse<List?>('abc'), null); // Invalid format
    },
  );
}