OpenApi: Multiple array properties of the same type do not get the correct type reference

[Jan-Weiss]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When generating an OpenApi document from a class which has more than one collection property (List, array, IEnumerable) of the same type, only the first property gets the correct reference to the type. The other properties are always Any.

For example this object:

internal record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
{
    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
}

internal record WeatherForeCasts(WeatherForecast[] Germany, WeatherForecast[] France);

results in the following OpenApi Document:

{
  "openapi": "3.0.1",
  "info": {
    "title": "OpenApiMulitpleListsOfSameType | v1",
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "https://localhost:7253/"
    }
  ],
  "paths": {
    "/weatherforecasts": {
      "get": {
        "tags": [
          "OpenApiMulitpleListsOfSameType"
        ],
        "operationId": "GetWeatherForecasts",
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/WeatherForeCasts"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "WeatherForecast": {
        "required": [
          "date",
          "temperatureC",
          "summary"
        ],
        "type": "object",
        "properties": {
          "date": {
            "type": "string",
            "format": "date"
          },
          "temperatureC": {
            "type": "integer",
            "format": "int32"
          },
          "summary": {
            "type": "string",
            "nullable": true
          },
          "temperatureF": {
            "type": "integer",
            "format": "int32"
          }
        }
      },
      "WeatherForeCasts": {
        "required": [
          "germany",
          "france"
        ],
        "type": "object",
        "properties": {
          "germany": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/WeatherForecast"
            }
          },
          "france": {
            "type": "array",
            "items": { }
          }
        }
      }
    }
  },
  "tags": [
    {
      "name": "OpenApiMulitpleListsOfSameType"
    }
  ]
}

The properties "Germany" and "France" are both collections of the same type, but only the first (Germany) gets the type referenced in the OpenApi document.

Expected Behavior

Every collection property of the same type gets a reference to that type in the OpenApi document.

Steps To Reproduce

Clone this repository.
Run the Project and navigate to the OpenApi Document (/openapi/v1.json) to see the issue.

Exceptions (if any)

No response

.NET Version

9.0.302

Anything else?

Microsoft.OpenApi version 9.0.8

There is an issue for this in the OpenApi.NET repository: microsoft/OpenAPI.NET#2443

[MihuBot]

I'm a bot. Here are possible related and/or duplicate issues (I may be wrong):

• OpenAPI generation *still* doesn't work with the simplest model with multiple collections in .net 9 #62079
• [OpenApi] $ref not generated for identical lists in same class #63096
• OpenAPI with two collections of same type generates weird internal ref #60931
• Only references the first list correctly - OpenAPI definition #60972
• Open Api fails to generate correct schema type for some properties #61407

[Jan-Weiss]

Seems like this is a duplicate of multiple closed issues.