Default values for enum are not written

[WolfgangHG]

I have this snippet in a model class (I tried both DefaultValue with enum and with string - of course I would prefer the first version):

public class WeatherForecast
{
  [DefaultValue(DayOfWeek.Wednesday)]
  public System.DayOfWeek EnumValue { get; set; } = DayOfWeek.Wednesday;

  [DefaultValue(nameof(DayOfWeek.Wednesday))]
  public System.DayOfWeek EnumValueWithStringDefault { get; set; } = DayOfWeek.Wednesday;
}

The OpenAPI file generated by Swashbuckle does not define the default value:

  "components": {
    "schemas": {
      "DayOfWeek": {
        "enum": [
          "Sunday",
          "Monday",
          "Tuesday",
          "Wednesday",
          "Thursday",
          "Friday",
          "Saturday"
        ],
        "type": "string"
      },
      "WeatherForecast": {
        "type": "object",
        "properties": {
          "enumValue": {
            "$ref": "#/components/schemas/DayOfWeek"
          },
          "enumValueWithStringDefault": {
            "$ref": "#/components/schemas/DayOfWeek"
          }
        },

I would like to see a default value for the enum values. But default values for "$ref" properties seem to be difficult to handle, as no further properties are allowed when "$ref" is used.

According to the sample at https://www.github.com/OpenAPITools/openapi-generator/issues/14689, the schema could look like this:

  "components": {
    "schemas": {
      ...
      "WeatherForecast": {
        "type": "object",
        "properties": {
          "enumValue": {
            "allOf": [
              {
                "$ref": "#/components/schemas/DayOfWeek"
              }],
            "default": "Wednesday"
          },
          "enumValueWithStringDefault": {
            "allOf": [
              {
                "$ref": "#/components/schemas/DayOfWeek"
              }],
            "default": "Wednesday"
          }
        },

I found this stackoverflow post which suggests an easier syntax. But I did not find any hint that this is allowed in the 3.1.1 spec

The sample model class can be found in https://github.com/WolfgangHG/Swashbuckle_Discussion3709/ (used for a previous discussion) - start the project using the launch profile "WebApiSwaggerVersion".

[martincostello]

It doesn't say which version of OpenAPI you're using in your application, but this is a constraint of OpenAPI 3.0 documents. When a $ref to another schema is generated, defaults (as well as other properties) aren't written to the document.

From me double-checking this locally, the default is written when generating an OpenAPI 3.1 document.

The default version generated by Swashbuckle.AspNetCore is 3.0.

[martincostello]

Sorry, I should also clarify that there's also a bug that prevents this working for OpenAPI 3.1 documents when it should.

[martincostello]

#3858

[WolfgangHG]

Many thanks for fixing this!

I am not sure whether OpenAPI 3.1 allows default values for enums (the StackOverflow link said so) - I did not find a hint in the spec.