Is there an existing issue for this?

• I have searched the existing issues

Current behavior

My sort param is used like ?sort[][created_on]=desc so I desire some openapi json like

"/some-endpoint": {
  "get": {
    "operationId": "SomeController_list",
    "parameters": [
      {
        "required": false,
        "name": "sort",
        "in": "query",
        "schema": {
          "example": [ { "created_on": "desc" } ],
          "type": "array",
          "items": {
            "type": "object",
            "additionalProperties": { "type": "string", "enum": [ "asc", "desc" ] }
          }
        }
      }
    ]
  }
},

but instead, nestjs/swagger is generating the get.paramaters[0].schema with an incorrect schema for the items field

{
  "required": false,
  "name": "sort",
  "in": "query",
  "schema": {
    "default": [ { "created_on": "desc" } ],
    "example": [ { "created_on": "desc" } ],
    "type": "array",
    "items": { "type": "array" }
  }
}

In my case I am using @anatine/zod-openapi in combination with @nestjs/swagger to generate the docs; I am not using decorators besides @ApiQuery({ type: SomeClass }) where SomeClass is generated by a zod plugin. As I explain below, this issue does appear to be with @nestjs/swagger though, not the zod plugin.

I can see that the correct metadata gets passed to transformToArraySchemaProperty:

{
  "type": "array",
  "items": {
    "type": "object",
    "additionalProperties": {
      "type": "string",
      "enum": ["asc", "desc"]
    }
  },
  "example": [{ "created_on": "desc" }],
  "required": false,
  "isArray": true
}

and that on line 550 that type is literally the string 'array' so the first part of the ternary is used, whereas I need the 2nd part of the ternary to be used.

Minimum reproduction code

https://github.com/nestjs/swagger

Steps to reproduce

No response

Expected behavior

The transformToArraySchemaProperty method correctly sets the items schema.

Package version

11.2.1

NestJS version

11.1.8

Node.js version

v22.16.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response