OpenAPITools / OpenAPITools/openapi-generator

[BUG] [kotlin-spring] MissingKotlinParameterException instead of BeanValidation exception for missing required property

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Issue: Bug Server: Kotlin
Dominant language
Java
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Description

Bug Report Checklist
  • Have you provided a full/minimal spec to reproduce the issue?
  • Have you validated the input using an OpenAPI validator (example)?
  • What's the version of OpenAPI Generator used?
  • Have you search for related issues/PRs?
  • What's the actual output vs expected output?
  • [Optional] Bounty to sponsor the fix (example)
Description

I defined a required property but instead of getting a bean validation exception, I get a MissingKotlinParameterException:

com.fasterxml.jackson.module.kotlin.MissingKotlinParameterException: Instantiation of [simple type, class dto.Component] value failed for JSON property type due to missing (therefore NULL) value for creator parameter type which is a non-nullable type
 at [Source: (PushbackInputStream); line: 1, column: 2] (through reference chain: dto.Component["type"])

Here is the generated DTO:

data class Component (
        @get:NotNull 
        @ApiModelProperty(required = true, value = "")
        @JsonProperty("type") val type: kotlin.String,

        @ApiModelProperty(value = "")
        @JsonProperty("model") val model: kotlin.String? = null
) 

It seems validation is done after the dto is instantiated... and as a required field is null, it can't create a new instance of this dto.

openapi-generator version

kotlin-spring with 4.2.2

OpenAPI declaration file content or url
Component:
  type: object
  required:
    - type
  properties:
    type:
      type: string
    model:
      type: string

Contributor guide

Open the contributing guide

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 reproducing the issue with the provided Component schema and generated kotlin-spring DTO, focusing on the interaction between Jackson construction and bean validation. Compare the MissingKotlinParameterException with the expected Bean Validation failure; done means a missing required type is reported through bean validation instead of preventing DTO instantiation.

Written by the indexing model from the issue text.

Assessment

Tech stack
kotlin, openapi, spring
Domain
api, backend, testing
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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