RicoSuter/NSwag

After upgrade core 2.2=>3.1, class with inheritance is shown as object

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#3141 opened on Nov 3, 2020

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help wantedproject: NSwag.AspNetCore

Description

In 2.2, the controllers accepting a paramater of DataSourceLoadOptions correctly showed the structure of the inherited DataSourceLoadOptionsBase. This is no longer the case in 3.1 - it is now just shown as an object. Any ideas how I can fix this?

[ModelBinder(BinderType = typeof(DataSourceLoadOptionsBinder))]
public class DataSourceLoadOptions : DataSourceLoadOptionsBase
{
    public IList CustomQueryParams { get; set; }

}

public class DataSourceLoadOptionsBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        var loadOptions = new DataSourceLoadOptions();
        DataSourceLoadOptionsParser.Parse(loadOptions, key => bindingContext.ValueProvider.GetValue(key).FirstOrDefault());
        var _customQueryParams = bindingContext.ValueProvider.GetValue("customQueryParams").FirstOrDefault();
        if (_customQueryParams != null)
        {
            loadOptions.CustomQueryParams = JsonConvert.DeserializeObject<IList>(_customQueryParams, new JsonSerializerSettings
            {
                DateParseHandling = DateParseHandling.None
            });
        }
        bindingContext.Result = ModelBindingResult.Success(loadOptions);
        return Task.CompletedTask;
    }
}

Contributor guide

Tech stack
csharp
Domain
backendapidocumentation
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic understanding of C# inheritanceFamiliarity with NSwag schema generation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The issue is that after upgrading from NSwag 2.2 to 3.1, inherited types like DataSourceLoadOptions are shown as 'object' instead of displaying their full structure. To resolve this, one should investigate changes in NSwag's type resolution logic between versions. Key files to examine include the Schema generation code, possibly `JsonSchemaGenerator` or related classes, and how reflection handles inheritance in the new version. The maintainers may have introduced a regression in the handling of type inheritance for model binding contexts. Look for tests related to inheritance and ensure that the schema generation correctly traverses base types. Also, check the `SystemTextJson` or `NewtonsoftJson` settings that might affect how types are processed.