[BUG] [Kotlin][Client] Query params are not exploded properly.

[maksim-kosolapov]

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?
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Description

It's not possible to use request objects in the API (e.g. findItems(SearchRequest(name, status, fromDate, ...))). One more example is a pagination parameter, something like Page(size,offset). I'd like to use a model in the API but it's not possible at the moment.

Kotlin Client generator is not exploding a query object properly. It uses the object toString() method, so API request doesn't work. See OpenAPI Parameter Serialization.

openapi-generator version

v7.11.0

OpenAPI declaration file content or url

This file has objects in the query parameters

Generation Details

./bin/generate-samples.sh ./bin/configs/kotlin*

Steps to reproduce

Generate Kotlin Client for this spec. It's clear from the generated code that object query params are not exploded properly. So API calls won't work properly using this generated client.

Related issues/PRs

Have not found any reported issues.

Suggest a fix

Fix #20714