OpenApi generate duplicate schemas

[oPreis-Systecs]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

In OpenApi (Version 9.0.4) schema json there are duplicate schemas if i use arrays.

Expected Behavior

Schemas should not duplicate.

Steps To Reproduce

Controller methods:

[HttpGet("new")]
[Produces("application/json")]
[ProducesResponseType((int)HttpStatusCode.OK, Type = typeof(IEnumerable<EventDto>))]
public async Task<IActionResult> GetAllEventsWithImages()
{
    try
    {
        var events = await _eventLogic.GetAllNewEventsAsync();
        return Ok(events);
    }
    catch (Exception ex)
    {
        _logger.LogError(ex, "Error while fetching new events.");
        return StatusCode((int)HttpStatusCode.InternalServerError, InternalServerErrorMessage);
    }
}

[HttpGet("{id:guid}")]
[Produces("application/json")]
[ProducesResponseType((int)HttpStatusCode.OK, Type = typeof(EventDto))]
public async Task<IActionResult> GetEventById(Guid id)
{
    _logger.LogInformation("Fetching event with ID {EventId}", id);
    var eventDto = await _eventLogic.GetEventByIdAsync(id);

    if (eventDto == null)
    {
        _logger.LogWarning("Event with ID {EventId} not found", id);
        return NotFound($"Event with ID {id} not found");
    }

    return Ok(eventDto);
}

Dto:

public class EventDto
{
    public Guid Id { get; set; }
    public Guid? CreatorId { get; set; }
    public string? InputText { get; set; }
    public string? OutputText { get; set; }
    public EventStatus? Status { get; set; }

    public IEnumerable<ImageDto> Images { get; set; } = new List<ImageDto>();
    public IEnumerable<CollectionDto> Collections { get; set; } = new List<CollectionDto>();
}

Generated schema:

{
  "openapi": "3.0.1",
  "info": {
    "title": "Systecs.PortfolioManager.Server | v1",
    "version": "1.0.0"
  },
  "paths": {
    "/api/Event/new": {
      "get": {
        "tags": [
          "Event"
        ],
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "type": "array",
                  "items": {
                    "$ref": "#/components/schemas/EventDto"
                  }
                }
              }
            }
          }
        }
      }
    },
    "/api/Event/{id}": {
      "get": {
        "tags": [
          "Event"
        ],
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "schema": {
              "type": "string",
              "format": "uuid"
            }
          }
        ],
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/EventDto2"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "CollectionDto": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "name": {
            "type": "string"
          },
          "surname": {
            "type": "string"
          },
          "description": {
            "type": "string",
            "nullable": true
          },
          "date": {
            "type": "string",
            "format": "date-time"
          },
          "imageId": {
            "type": "string",
            "format": "uuid",
            "nullable": true
          },
          "image": {
            "$ref": "#/components/schemas/ImageDto2"
          },
          "events": {
            "type": "array",
            "items": { }
          }
        }
      },
      "CollectionDto2": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "name": {
            "type": "string"
          },
          "surname": {
            "type": "string"
          },
          "description": {
            "type": "string",
            "nullable": true
          },
          "date": {
            "type": "string",
            "format": "date-time"
          },
          "imageId": {
            "type": "string",
            "format": "uuid",
            "nullable": true
          },
          "image": {
            "$ref": "#/components/schemas/ImageDto2"
          },
          "events": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/EventDto"
            }
          }
        }
      },
      "EventDto": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "creatorId": {
            "type": "string",
            "format": "uuid",
            "nullable": true
          },
          "inputText": {
            "type": "string",
            "nullable": true
          },
          "outputText": {
            "type": "string",
            "nullable": true
          },
          "status": {
            "$ref": "#/components/schemas/NullableOfEventStatus"
          },
          "images": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/ImageDto"
            }
          },
          "collections": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/CollectionDto"
            }
          }
        }
      },
      "EventDto2": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "creatorId": {
            "type": "string",
            "format": "uuid",
            "nullable": true
          },
          "inputText": {
            "type": "string",
            "nullable": true
          },
          "outputText": {
            "type": "string",
            "nullable": true
          },
          "status": {
            "$ref": "#/components/schemas/NullableOfEventStatus"
          },
          "images": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/ImageDto"
            }
          },
          "collections": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/CollectionDto2"
            }
          }
        }
      },
      "ImageDto": {
        "required": [
          "imageData"
        ],
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "imageData": {
            "type": "string",
            "format": "byte"
          },
          "contentType": {
            "type": "string"
          },
          "type": {
            "$ref": "#/components/schemas/ImageType"
          }
        }
      },
      "ImageDto2": {
        "required": [
          "imageData"
        ],
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "imageData": {
            "type": "string",
            "format": "byte"
          },
          "contentType": {
            "type": "string"
          },
          "type": {
            "$ref": "#/components/schemas/ImageType"
          }
        },
        "nullable": true
      },
      "ImageType": {
        "type": "integer"
      },
      "NullableOfEventStatus": {
        "type": "integer",
        "nullable": true
      }
    }
  },
  "tags": [
    {
      "name": "Event"
    }
  ]
}

Exceptions (if any)

No response

.NET Version

9.0.200

Anything else?

No response

[balukin]

Probably the same issue here. It was happening prior to 9.0.4, too. I'm using minimal API definitions (WithOpenApi() extension)

public class Response
{
    public Dictionary<string, SomeCustomType>? GroupedResults { get; set; } = new();
    public SomeCustomType? OverallResults { get; set; } 
}

Two schemas are generated #/components/schemas/SomeCustomType and #/components/schemas/SomeCustomType2.

Temporary I can work around this with following configuration but it's too fragile to be a long term solution. Gets API clients to generate in dev loop with no errors, at least.

services.AddOpenApi(options =>
{
    options.AddSchemaTransformer((schema, context, cancellationToken) =>
    {
        if (schema.Properties is not null)
        {
            if (schema.Properties.TryGetValue("overallResults", out var overallResultsRef))
            {
                overallResultsRef.Nullable = true; 
                overallResultsRef.Reference = new OpenApiReference()
                {
                    Id = "SomeCustomType", // forces SomeCustomType instead of SomeCustomType2
                    Type = ReferenceType.Schema,
                };
            }
        }

        return Task.CompletedTask;
    });

});

Strangely enough, resulting JSON doesn't have nullable set to true on overallResults after this modification - I don't know why.

"groupedResults": {
    "type": "object",
    "additionalProperties": {
        "$ref": "#/components/schemas/SomeCustomType"
    },
    "nullable": true
    },
    "overallResults": {
        // would be suffixed with `2` and cause entire new schema to generate without workaround
    "$ref": "#/components/schemas/SomeCustomType"
    },

[captainsafia]

Fixed in .NET 10.

#:sdk Microsoft.NET.Sdk.Web
#:property TargetFramework=net10.0
#:property PublishAoT=false
#:package Microsoft.AspNetCore.OpenApi@10.0.0-preview.7.*

using Microsoft.AspNetCore.Mvc;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddOpenApi();

var app = builder.Build();

app.MapOpenApi();

app.MapGet("/response", () =>
{
    var response = new Response
    {
        GroupedResults = new Dictionary<string, SomeCustomType>
        {
            { "Group1", new SomeCustomType { /* initialize properties */ } },
            { "Group2", new SomeCustomType { /* initialize properties */ } }
        },
        OverallResults = new SomeCustomType { /* initialize properties */ }
    };

    return TypedResults.Ok(response);
});

app.MapGet("/event", () =>
{
    var eventDto = new EventDto
    {
        Id = Guid.NewGuid(),
        CreatorId = Guid.NewGuid(),
        InputText = "Sample input",
        OutputText = "Sample output"
    };

    return TypedResults.Ok(eventDto);
});

app.MapGet("/events", () =>
{
    var events = new List<EventDto>
    {
        new EventDto
        {
            Id = Guid.NewGuid(),
            CreatorId = Guid.NewGuid(),
            InputText = "Sample input 1",
            OutputText = "Sample output 1",
        },
        new EventDto
        {
            Id = Guid.NewGuid(),
            CreatorId = Guid.NewGuid(),
            InputText = "Sample input 2",
            OutputText = "Sample output 2",
        }
    };

    return TypedResults.Ok(events);
});



app.Run();

public class Response
{
    public Dictionary<string, SomeCustomType>? GroupedResults { get; set; } = new();
    public SomeCustomType? OverallResults { get; set; }
}

public class SomeCustomType
{
    // Define properties for SomeCustomType
    public string Property1 { get; set; }
    public int Property2 { get; set; }
}

public class EventDto
{
    public Guid Id { get; set; }
    public Guid? CreatorId { get; set; }
    public string? InputText { get; set; }
    public string? OutputText { get; set; }
}

{
  "openapi": "3.1.1",
  "info": {
    "title": "61408 | v1",
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "http://localhost:5000/"
    }
  ],
  "paths": {
    "/response": {
      "get": {
        "tags": [
          "61408"
        ],
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Response"
                }
              }
            }
          }
        }
      }
    },
    "/event": {
      "get": {
        "tags": [
          "61408"
        ],
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/EventDto"
                }
              }
            }
          }
        }
      }
    },
    "/events": {
      "get": {
        "tags": [
          "61408"
        ],
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "type": "array",
                  "items": {
                    "$ref": "#/components/schemas/EventDto"
                  }
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "EventDto": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "creatorId": {
            "type": [
              "null",
              "string"
            ],
            "format": "uuid"
          },
          "inputText": {
            "type": [
              "null",
              "string"
            ]
          },
          "outputText": {
            "type": [
              "null",
              "string"
            ]
          }
        }
      },
      "Response": {
        "type": "object",
        "properties": {
          "groupedResults": {
            "type": [
              "null",
              "object"
            ],
            "additionalProperties": {
              "$ref": "#/components/schemas/SomeCustomType"
            }
          },
          "overallResults": {
            "$ref": "#/components/schemas/SomeCustomType"
          }
        }
      },
      "SomeCustomType": {
        "type": [
          "null",
          "object"
        ],
        "properties": {
          "property1": {
            "type": "string"
          },
          "property2": {
            "pattern": "^-?(?:0|[1-9]\\d*)$",
            "type": [
              "integer",
              "string"
            ],
            "format": "int32"
          }
        }
      }
    }
  },
  "tags": [
    {
      "name": "61408"
    }
  ]
}