Request JSON: Type 'bool' is not a subtype of type 'String' in type cast

[acarlstein]

Summary

When doing a POST rest call, if the JSON request contains a boolean value instead of a String value, then we get Error: type 'bool' is not a subtype of type 'String' in type cast. This goes against The JavaScript Object Notation (JSON) Data Interchange Format - RFC-7156.

Description

This SomeRequest class:

class SomeRequest {
  String id;
  bool advanced;

  FollowerUpdateRequest({
    required this.id,
    this.advanced = false
  });

  Map<String, dynamic> toJson(){
    return {
      'id': id,
      'advanced': advanced
    };
  }

  @override
  String toString(){
    return jsonEncode(toJson());
  }

}

will create the following JSON (example):

{
  'id': "xxx-xxxx-xxx",
  'advanced': false
};

However, when we use this request with http.post like this:

Future<SomeResponse> fetch(
    SomeRequest data
 ) async {
    Uri uri = Uri.parse("some url");
    final response = await http.post(
      uri,
      body: data.toJson()
    );
    if (response.statusCode == 200){
      SomeResponse resp = SomeResponse.fromJson(
        jsonDecode(response.body)
      );
      return resp;
    } else {
      throw Exception('print this exception');
    }
  }

We get this error:

flutter: [!] Info: Error: type 'bool' is not a subtype of type 'String' in type cast

If we change the type of advanced from bool to String, this error disappears, but the server will reject such JSON because it validates that advanced should be boolean.

If we read The JavaScript Object Notation (JSON) Data Interchange Format - RFC-7156, we could read that JSON can represent four primitive types (strings, numbers, booleans, and null) and two structured types (objects and arrays)..

Acceptance Criteria

Follow the documentation in The JavaScript Object Notation (JSON) Data Interchange Format - RFC-7156 so any request with a body, will accept a JSON body that contains a boolean, following rule of JSON can represent four primitive types (strings, numbers, booleans, and null) and two structured types (objects and arrays).

Extra Information

flutter doctor -v:

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    • ANDROID_SDK_ROOT = /opt/homebrew/share/android-commandlinetools
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• No issues found!

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[brianquinlan]

Hi @acarlstein

As far as I can see, this problem isn't related to package:http, it is related to jsonEncode in dart:convert.

Also, I think that something else is going on here since jsonEncode can encode booleans just fine.

Could you try to create a minimal reproduction and, if you are convinced that there is still a bug, file one with the Dart SDK?