[BUG][Kotlin][Multiplatform] Support for date format is missing for kotlinx-datetime library

[ggajews]

Bug Report Checklist

• [x] Have you provided a full/minimal spec to reproduce the issue?
• [x] Have you validated the input using an OpenAPI validator (example)?
• [x] Have you tested with the latest master to confirm the issue still exists?
• [x] Have you searched for related issues/PRs?
• [x] What's the actual output vs expected output?
• [ ] [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

For the input data in Schema:

        shipDate:
          type: string
          format: date-time

generator produces

@SerialName(value = "shipDate") val shipDate: java.time.LocalDate? = null

Which is incorrect for multiplatform, and breaks the build

openapi-generator version

7.2.0

OpenAPI declaration file content or url

Just edit the original petstore.yaml and change shipDate to date:

Order:
    title: Pet Order
    description: An order for a pets from the pet store
    type: object
    properties:
      id:
        type: integer
        format: int64
      petId:
        type: integer
        format: int64
      quantity:
        type: integer
        format: int32
      shipDate:
        type: string
        format: date
      status:
        type: string
        description: Order Status
        enum:
          - placed
          - approved
          - delivered
      complete:
        type: boolean
        default: false
    xml:
      name: Order

Generation Details

Just run sample generator

Steps to reproduce

Generate kotlin-multiplatform-kotlinx-datetime sample

Related issues/PRs

none

Suggest a fix

Probably registering a date type in KotlinClientCodegen.java should be enough

private void processKotlinxDate() {
        additionalProperties.put(DateLibrary.KOTLINX_DATETIME.value, true);

       typeMapping.put("date", "kotlinx.datetime.LocalDate");

        typeMapping.put("date-time", "kotlinx.datetime.Instant");
        typeMapping.put("DateTime", "Instant");
        importMapping.put("Instant", "kotlinx.datetime.Instant");
    }

[andresilveirah]

Just adding my two cents. Ran into the same issue using 7.3.0 and 7.2.0. Version 7.1.0 doesn't have the same problem.

[mreichelt]

We can confirm - we have the problem using 7.3.0 ❌ - version 7.1.0 works without issues ✅ . It looks like the kotlinx-multiplatform serialization part of the openapi generator is not covered by unit tests.