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• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
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• What's the actual output vs expected output?
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Description

Wrapping query params in a containing object so that the generated client method only has one param instead of X params, but when the query param is an array, the generated code always builds a CSV with the contents of the array, instead of handling it as "multi".

openapi-generator version

It's not a regression. Wrapping object were supported after 7.2.0 thanks to this PR but it is not working correctly when having array properties.

OpenAPI declaration file content or url

paths:
  /api/search:
    get:
      operationId: Search
      parameters:
        - name: object-param
          in: query
          required: true
          schema:
            type: object
            properties:
              someArray:
                type: array
                items:
                  type: string

• The example is an adaptation from modules/openapi-generator/src/test/resources/3_0/java/explode-query-parameter.yaml

Generation Details

Java language, WebClient library, but also with RestTemplate.

Steps to reproduce

By adapting the upper mentioned file, execute the following test
JavaClientCodegenTest.shouldProperlyExplodeWebClientQueryParameters
adding

.bodyContainsLines("queryParams.putAll(apiClient.parameterToMultiValueMap(ApiClient.CollectionFormat.valueOf(\"multi\".toUpperCase(Locale.ROOT)), \"someArray\"," + " objectParam.getSomeArray()));");

Expected would be to handle the array query param as "multi" since explode defaults to true.
Actual: it's treated as csv because the collectionFormat param is null.

Related issues/PRs

#17441

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