[BUG] additionalProperties key from schema is not handled correctly

[dJani97]

Describe the bug
Using "additionalProperties" in a definition causes the generated field to be of type Object.

To Reproduce
The swagger json can be found in this example on swaggerhub.

Running swagger-dart-code-generator on this json results in the ExampleDTO having a generic Object? examples field instead of Map<String, List<EmbeddedExampleDTO>> examples described in the swagger file.

Here is a snippet from the generated Dart class:

@JsonSerializable(explicitToJson: true)
class ExampleDTO {
  ExampleDTO({
    this.examples,
  });

  factory ExampleDTO.fromJson(Map<String, dynamic> json) =>
      _$ExampleDTOFromJson(json);

  @JsonKey(name: 'examples')
  final Object? examples;

  // (...)
}

Expected behavior
The example field should be generated as Map<String, List<EmbeddedExampleDTO>> examples.

For example, the Export > Client SDK > Dart function on SwaggerHub seems to generate a proper implementation:

class ExampleDTO {
  Map<String, List<EmbeddedExampleDTO>> examples = {};
  
  // (...)
}

Library version used:
swagger_dart_code_generator: ^2.3.2

Additional context
I noticed that this problem was already referenced in #58 which was closed with the message "fixed all issues in 1.2.0 version".

[fryette]

I think that feature can be quite easily implemented.

We will add it to our roadmap and will try to deliver it this month.

Documentation: https://swagger.io/docs/specification/data-models/dictionaries/

[fryette]

So, we double-checked this issue and seems Expected result is not achievable.
If a property has additional properties it means that it's a dictionary.
For example for that case(see below), we see 2 properties, "default": "string", and a list of Models and because it's the dictionary we cannot generate a regular model or Map<String, List<EmbeddedExampleDTO>>. It should be simple Map<String, dynamic> in my understanding.

  ExampleDTO:
    type: object
    required:
      - examples
    properties:
      examples:
        type: object
        properties:
          default:
            type: string
        additionalProperties:
          type: array
          items:
            $ref: '#/definitions/EmbeddedExampleDTO'

We are going to change generated field from Object to Map<String, dynamic> and let users parse it as they want.