softwaremill / softwaremill/tapir

[BUG] Open API Parameter Serialization

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Scala
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Description

Tapir version: 0.16.16

Scala version: 2.13.1

Describe the bug
I want to use objects in query parameters

  def jsonQuery[T: Encoder : Decoder : Schema](name: String): EndpointInput.Query[T] = {
    implicit val codec = Codec.string.mapDecode(x => decode[T](x).fold(
      x => DecodeResult.Error("json parse error", x),
      x => DecodeResult.Value(x)))(_.asJson.noSpaces)
      .schema(implicitly[Schema[T]])
    query[T](name)
  }

  val foo = endpoint.in("foo")
    .in(jsonQuery[Sort]("sort")).out(jsonBody[Sort])

Tapir generate this yaml

openapi: 3.0.1
info:
  title: API
  version: '1.0'
paths:
  /foo:
    get:
      operationId: getFoo
      parameters:
      - name: sort
        in: query
        required: true
        schema:
          $ref: '#/components/schemas/Sort'
      responses:
        '200':
          description: ''
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Sort'
components:
  schemas:
    Sort:
      required:
      - field
      - order
      type: object
      properties:
        field:
          type: string
        order:
          type: string

Open Api support 3 types of object serialization in query
https://swagger.io/docs/specification/serialization/#query

style:style explode:true /users?role=admin&firstName=Alex (default)
style:style explode:false  /users?id=role,admin,firstName,Alex
style:deepObject explode:true  /users?id[role]=admin&id[firstName]=Alex

Tapir doesn't add any style or explode parameters so url for endpoint should be

/foo?field=a&order=b

But such url doesn't work

Invalid value for: query parameter sort

Neither do

/foo?sort=field,a,order,b
/foo?sort[field]=a&sort[order]=b

I think Tapir should use deepObject:true in object query parameters and support urls like /foo?sort[field]=a&sort[order]=b

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by tracing Tapir's OpenAPI query-parameter generation and the corresponding query decoding for EndpointInput.Query, using the serialization styles and example URLs cited in the issue. Compare the generated specification with the supported request forms; done should make the chosen object serialization explicit and ensure the documented URL form is accepted consistently.

Written by the indexing model from the issue text.

Assessment

Tech stack
openapi, scala
Domain
api, backend-api-design
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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