dotnet/aspnetcore

Incorrect OpenAPI definition when using FromForm with IEnumerable parameters

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#62,328 创建于 2025年6月12日

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area-minimalfeature-openapihelp wanted

描述

Is there an existing issue for this?

  • I have searched the existing issues

Describe the bug

I'm using .NET 9 OpenAPI support. With the following endpoint:

app.MapPost("/api/documents", ([FromForm] int[] values) =>
{
    return TypedResults.Ok();
});

I get the following definition:

"requestBody": {
          "content": {
            "multipart/form-data": {
              "schema": {
                "type": "object",
                "properties": {
                  "values": {
                    "type": "array",
                    "items": {
                      "type": "integer",
                      "format": "int32"
                    }
                  }
                }
              }
            },
            "application/x-www-form-urlencoded": {
              "schema": {
                "type": "object",
                "properties": {
                  "values": {
                    "type": "array",
                    "items": {
                      "type": "integer",
                      "format": "int32"
                    }
                  }
                }
              }
            }
          },
          "required": true
        }

If, instead, I change the type to IEnumerable:

app.MapPost("/api/documents", ([FromForm] IEnumerable<int> values) =>
{
    return TypedResults.Ok();
});

The OpenAPI definition becomes:

"requestBody": {
          "content": {
            "multipart/form-data": {
              "schema": {
                "type": "array",
                "items": {
                  "type": "integer",
                  "format": "int32"
                }
              }
            },
            "application/x-www-form-urlencoded": {
              "schema": {
                "type": "array",
                "items": {
                  "type": "integer",
                  "format": "int32"
                }
              }
            }
          },
          "required": true
        },

.NET Version

9.0.301

贡献者指南

技术栈
csharp
领域
backendapi
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
3
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
1-3 hours
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
fresh
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
Basic understanding of ASP.NET CoreFamiliarity with OpenAPI
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
70
研究方向
Investigate the OpenAPI schema generation code for form parameters in the ASP.NET Core repository. Focus on how `IEnumerable<int>` with `[FromForm]` is handled compared to `int[]`. Look at the class `OpenApiRequestBodyFactory` or similar that processes form parameters. Check the existing tests for form based request bodies to understand expected behavior. Identify the code path that incorrectly produces an array schema instead of an object schema for IEnumerable parameters.