second level inheritance for UseOneOfForPolymorphism

[k0ka]

The issue or feature being addressed

The UseAllOfForInheritance option of schema generator only accounts for direct parents. It makes impossible to generate correct discriminator information for a big inheritance tree.

Example

data class structure:

[SwaggerDiscriminator("discriminator")]
[SwaggerSubType(typeof(SubSubType), DiscriminatorValue = nameof(SubSubType))]
abstract public class BaseType
{
}

abstract public class SubType : BaseType
{
}

public class SubSubType : SubType
{
    public int Property { get; set; }
}

Swagger generator options:

builder.Services.AddSwaggerGen(
    options =>
    {
        options.UseAllOfForInheritance();
        options.UseOneOfForPolymorphism();
        options.EnableAnnotations(true, true);
    });

Generated components of the json:

"components": {
    "schemas": {
      "SubSubType": {
        "type": "object",
        "properties": {
          "property": {
            "type": "integer",
            "format": "int32"
          }
        },
        "additionalProperties": false
      }
    }
  }

It doesn't include discriminator and BaseType definition.

If we remove SubType and make SubSubType child of BaseType we would get the expected generated components:

"components": {
    "schemas": {
      "BaseType": {
        "required": [
          "discriminator"
        ],
        "type": "object",
        "properties": {
          "discriminator": {
            "type": "string"
          }
        },
        "additionalProperties": false,
        "discriminator": {
          "propertyName": "discriminator",
          "mapping": {
            "SubSubType": "#/components/schemas/SubSubType"
          }
        }
      },
      "SubSubType": {
        "allOf": [
          {
            "$ref": "#/components/schemas/BaseType"
          },
          {
            "type": "object",
            "properties": {
              "property": {
                "type": "integer",
                "format": "int32"
              }
            },
            "additionalProperties": false
          }
        ]
      }
    }
  }

Details on the issue fix or feature implementation

This PR checks all parents until it finds the one which has this class defined as sub type. I added same assertions to test with one level assertions.

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[martincostello]

Could you also add an example like in the issue description to one of our integration test projects so we have a verification test for this scenario too please?

[k0ka]

Hello,

I added this case to NswagClientExample because it was the only integration test which enabled inheritance and polymorphic annotations.
Also, I found a problem in Annotation handler and fixed it. It was using only direct parent annotations to get type value.

[Eloyjr27]

ok, all is perfect