Why are responses nullable?

[vkhobor]

I was wondering what is the significance that the typescript client, and the go clients can return undefined and nil, even if there is no error(go), and no error was thrown(ts).

When does this happen? And why is this not converted to an error? How should I handle this case?

https://github.com/microsoftgraph/msgraph-sdk-go/blob/067c7ca48959fdc758e8798ad53887cd7e825d59/admin/admin_request_builder.go#L70
(return nil, nil)

https://github.com/microsoftgraph/msgraph-sdk-typescript/blob/1f898c60ebe711c571c8f940d46b7b4756b1deac/packages/msgraph-sdk-admin/admin/people/profileCardProperties/item/index.ts#L38
(response is typed as Response | undefined)

[baywet]

Hi,
Thank you for using kiota and for reaching out .
The reason why the responses are nullable is because a lot of APIs out there technically can return a 204 or a 201 with no content and most of them do not document that as part of their open API specification.
For that reason, instead of requiring everyone to amend their description, we made an assumption that this is common behavior and the client should account for that.
The alternative being if it's not strictly in the open API description and we don't get a content in the response to throw an exception instead and this would be pretty aggressive as a design decision. We already received some feedback that throwing exceptions on non-successful response status code is already an aggressive decision, so this is why we would probably not push further in that direction at this point.
I hope this clarifies the design decision here, let us know if you have any other questions.

[vkhobor]

Thanks. So basically this is the scenario? One response can return nothing other returns a schema. (and some APIs do not document this)

/pets:
  put:
    description: "Updates a pet, if created returns created otherwise ok"
    operationId: "addPet"
    requestBody:
      description: "Pet to add to the store"
      required: true
      content:
        application/json:
          schema:
            $ref: "#/components/schemas/NewPet"
    responses:
      200:
        description: "update successful"
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/Pet"
      201:
        description: "created"       
      default:
        description: "unexpected error"
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/Error"

Now I wonder if there would be multiple different 2xx status codes returned (but with the same data), how can I differentiate that when inspecting the response?

Also from quick testing

/pets:
 put:
   description: "Updates a pet, if created returns created otherwise ok"
   operationId: "addPet"
   requestBody:
     description: "Pet to add to the store"
     required: true
     content:
       application/json:
         schema:
           $ref: "#/components/schemas/NewPet"
   responses:
     200:
       description: "update successful"
       content:
         application/json:
           schema:
             $ref: "#/components/schemas/Pet"
     201:
       description: "created"
       content:
         application/json:
           schema:
             $ref: "#/components/schemas/NewPet"
     default:
       description: "unexpected error"
       content:
         application/json:
           schema:
             $ref: "#/components/schemas/Error"
             

Can I return different types on different 2xx responses? From the generated code it seems it still is typed as a single type for this response. Pet | undefined

[baywet]

Kiota does not support generating multiple types for different response status codes today here's an issue that captures that. #2317

[vkhobor]

For anyone wandering here I have found the related issue #3911, that should be upvoted if this affects you.