[BUG][Crystal] For an array of nullable items, the nullability is not respected

Description

I have an array of nullable integers in my specification. But the Crystal code generator produces Array(Int32) whereas I would expect Array(Int32?).

I also confirmed that the JSON parsing fails if the array actually contains a null.

openapi-generator version

openapi-generator-cli 7.16.0

OpenAPI declaration file content or url

openapi: 3.0.4
info:
  title: ""
  description: ""
  version: ""
paths:
  /api/v3/items/:
    get:
      operationId: get_items
      responses:
        "200":
          description: ""
          content:
            application/json:
              schema:
                type: object
                required: [ids]
                properties:
                  ids:
                    type: array
                    items:
                      type: integer
                      nullable: true
                      

Generation Details

openapi-generator-cli generate -i swagger.yaml -g crystal -o api

Steps to reproduce

Generate the code based on the above.

The content of the file api/src/openapi_client/models/get_items200_response.cr contains the following:

module OpenAPIClient
  class GetItems200Response
    include JSON::Serializable
    include YAML::Serializable

    # Required properties
    @[JSON::Field(key: "ids", type: Array(Int32), nillable: false, emit_null: false)]
    property ids : Array(Int32)

    # Initializes the object
    # @param [Hash] attributes Model attributes in the form of hash
    def initialize(@ids : Array(Int32))
    end

What I expect to see instead:

module OpenAPIClient
  class GetItems200Response
    include JSON::Serializable
    include YAML::Serializable

    # Required properties
    @[JSON::Field(key: "ids", type: Array(Int32?), nillable: false, emit_null: false)]
    property ids : Array(Int32?)

    # Initializes the object
    # @param [Hash] attributes Model attributes in the form of hash
    def initialize(@ids : Array(Int32?))
    end

Related issues/PRs

None. https://github.com/openapitools/openapi-generator/issues?q=is%3Aissue%20crystal%20nullable

Suggest a fix

cc @wing328

Start by reproducing the issue with the provided OpenAPI declaration and openapi-generator-cli generate -i swagger.yaml -g crystal -o api. Inspect the generated api/src/openapi_client/models/get_items200_response.cr and the Crystal generator’s handling of nullable array items. Done means the generated property and JSON field use Array(Int32?), and parsing an array containing null succeeds.