Org Web Adapter

Editing hungryroot/jira/be_7233_add_proper_schema_typing_for_discount_info_expand_on_v3_pairings_endpoint.org

:PROPERTIES:
:ID:       8f70e8e8-ffc2-4d2b-a0fc-c4624f2b764e
:END:
#+title: BE-7233 Add proper schema typing for discount_info expand on V3 pairings endpoint

- source :: https://hungryroot.atlassian.net/browse/BE-7233
- tags   :: [[id:3a477c02-e26d-40f7-a719-0aa1cd169dd8][Hungryroot API Project]]
- epic   :: [[id:86327fb4-0f66-4bc6-9068-c414cea77042][EP-411 Eng Parking Lot]]
- sprint :: [[id:211bb652-f918-4774-9611-ec6c3a77c72b][HR BE Sprint 105]]
- status :: [[id:4d41d978-e56f-45c1-88d1-e2c76510972e][Status - Complete]]

* Tasks
** DONE Try just adding the doc string to the extended schema :schema:apiv3:docs:work:bug:hungryroot:ep411:sprint105:be7233:
:PROPERTIES:
:ID:       c3fb14d9-f604-f465-739c-da987d8f6b39
:END:
* Tests
[[file:../../apis/hungryroot/v3.http::GET :host/api/v3/pairings/464473/?expand=ingredients%2Ctags%2Cnutrition%2Cdiscount_info&inventory_date=2024-01-15][API call]]

#+begin_src shell
curl -X 'GET' 'http://localhost:8000/api/v3/pairings/464473/?expand=ingredients%2Ctags%2Cnutrition%2Cdiscount_info' -H 'accept: application/json'
#+end_src

* Description
** Problem

The discount_info expandable field on the PairingStaticListViewset
(/api/v3/pairings) endpoint is missing proper schema typing. drf-spectacular
cannot infer the response shape from the SerializerMethodField that delegates to
PairingDiscountSerializer, so the generated OpenAPI schema falls back to an
untyped object:

#+begin_src json
"discount_info": {
    "additionalProp1": "string",
    "additionalProp2": "string",
    "additionalProp3": "string"
}
#+end_src

This means API consumers have no typed contract for this field -- frontend and
mobile clients cannot generate types from the schema, and the Swagger docs are
misleading.

** Expected

The OpenAPI schema should reflect the actual typed response from
PairingDiscountSerializer (defined in app/rest/shared/discount_serializer.py):

#+begin_src json
"discount_info": {
    "discount": null,
    "discount_percentage": null,
    "points_after_discount": null
}
#+end_src

With proper nullable number types so clients can generate accurate
TypeScript/Swift/Kotlin types from the spec.

** Approach

Add an @extend_schema_field decorator or inline OpenApiTypes annotation to the
get_discount_info method in PairingSerializer (app/rest/v3/pairing.py) so
drf-spectacular emits the correct schema.

Files

app/rest/v3/pairing.py -- PairingSerializer.get_discount_info

app/rest/shared/discount_serializer.py -- PairingDiscountSerializer