[BUG][typescript] parameter with integer enum fails when values include null

Bug Report Checklist

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

Description

With a query parameter of type nullable integer with enumerated allowed values including explicit null the typescript generator fails with a nasty exception.

I'm new to OpenAPI spec and may have misinterpreted what's allowed.

I'd have thought this was a legal spec based on running it through a spec validator.

openapi-generator version

v7.8.0 and latest on main

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: Bug Repro
  version: 1.0.0
paths:
  /path:
    description: Bug repro
    get:
      description: Bug repro
      parameters:
        - in: query
          name: bug
          description: Bug repro
          schema:
            type: integer
            nullable: true
            enum: [null,1,2]
          example: 2
      responses:
        "200":
          description: OK

Generation Details

openapi-generator generate -I spec.yaml -g typescript -o ../bug

I have run this with a brew installed tool and then later with java debugger on a checkout of main.

Steps to reproduce

Run the generator using any typescript variation with the minimal config above to yield a fatal error whose cause is a NullPointerExpection.

Exception in thread "main" java.lang.RuntimeException: Could not process operation:
  Tag: class Tag {
    name: default
    description: null
    externalDocs: null
}
  Operation: null
  Resource: get /path
  Schemas: {}
  Exception: null
	at org.openapitools.codegen.DefaultGenerator.processOperation(DefaultGenerator.java:1609)
	at org.openapitools.codegen.DefaultGenerator.processPaths(DefaultGenerator.java:1474)
	at org.openapitools.codegen.DefaultGenerator.generateApis(DefaultGenerator.java:673)
	at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:1306)
	at org.openapitools.codegen.cmd.Generate.execute(Generate.java:535)
	at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
	at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)
Caused by: java.lang.NullPointerException
	at org.openapitools.codegen.languages.AbstractTypeScriptClientCodegen.numericEnumValuesToEnumTypeUnion(AbstractTypeScriptClientCodegen.java:727)
	at org.openapitools.codegen.languages.AbstractTypeScriptClientCodegen.getParameterDataType(AbstractTypeScriptClientCodegen.java:671)
	at org.openapitools.codegen.DefaultCodegen.fromParameter(DefaultCodegen.java:5138)
	at org.openapitools.codegen.DefaultCodegen.fromOperation(DefaultCodegen.java:4648)
	at org.openapitools.codegen.DefaultGenerator.processOperation(DefaultGenerator.java:1577)
	... 6 more

Related issues/PRs

N/A

Suggest a fix

numericEnumValuesToEnumTypeUnion in AbstractTypescriptClientCodegen.java (line 727) is where the problem emnates.

This method is expecting the list of values to all be non-null as it calls toString() on each value. However this fails when there is an explicit null in the list.

My naive suggestion is a null check and in the case where value == null add "null" to the stringValues list.

Start in AbstractTypeScriptClientCodegen.java at numericEnumValuesToEnumTypeUnion, then trace its use through getParameterDataType for the reported query parameter. Run the provided openapi-generator command with the minimal spec and verify generation no longer fails with a NullPointerException when the integer enum includes null.