Encoding not exploding a property in requestBody in swagger-ui

Question

The parameter is not being exploded into separate fields, and i cant get my head wrapped around why.

This is my yaml, using OpenApi 3.0

paths:
  /match/started:
    post:
      tags:
        - match
      summary: 'Callback for when a game has started.'
      operationId: 'App\Http\Controllers\Api\V1\MatchController::started'
      requestBody:
        description: 'Something something batman!'
        required: true
        content:
          multipart/form-data:
            schema:
              required:
                - match_uuid
              properties:
                game_uuid:
                  type: string
                player_uuids:
                  type: array
                  items:
                    type: string
              type: object
            encoding:
              player_uuids:
                style: form
                explode: true
      responses:
        200:
          description: 'success response'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Api_V1_Match_Started'

this is the curl request swagger is giving me (BAD)

curl -X POST "https://editor.swagger.io/api/v1/match/started" -H "accept: application/json" -H "Content-Type: multipart/form-data" -F "game_uuid=test" -F "player_uuids=aaa,bbb,ccc"

where you can see the last parameter is -F "player_uuids=aaa,bbb,ccc" and it should be -F "player_uuids=aaa" -F "player_uuids=bbb" -F "player_uuids=ccc"

so the full request should look like this:

curl -X POST "https://editor.swagger.io/api/v1/match/started" -H "accept: application/json" -H "Content-Type: multipart/form-data" -F "game_uuid=test" -F "player_uuids=aaa" -F "player_uuids=bbb" -F "player_uuids=ccc"

Answer 1

There's currently no way to define your scenario (a multipart request with an exploded array) with OpenAPI, because the explode and style behavior is only defined for application/x-www-form-urlencoded but not for multipart/*:

style
... This property SHALL be ignored if the request body media type is not application/x-www-form-urlencoded.

explode
... This property SHALL be ignored if the request body media type is not application/x-www-form-urlencoded.

Related discussion: Swagger UI: Submit An Array of Integer Elements In formdata

You might want to file an enhancement request with the OpenAPI Spec.