[BUG] Missing serverConf variable when emitting QT C++ clients

Description

QT C++ Client code generator generates references to a serverConf variable, but it does not emit the definition of this variable.

/tmp/client/OAIExternalEngineApi.cpp: In member function ‘void OpenAPI::OAIExternalEngineApi::initializeServerConfigs()’:
/tmp/client/OAIExternalEngineApi.cpp:39:5: error: ‘serverConf’ was not declared in this scope; did you mean ‘_serverConfigs’?
   39 |     serverConf.append(OAIServerConfiguration(
      |     ^~~~~~~~~~
      |     _serverConfigs

openapi-generator version

This problem happens at HEAD.

OpenAPI declaration file content or url

It's the lichess.org official API. There's a download link right at the top.

Generation Details

Happens with the C++ QT Client API generator.

Steps to reproduce

To reproduce the original issue, install QT build dependencies, then:

• go to https://lichess.org/api, click the "Download" link, save openapi.json somewhere
• java -jar target/openapi-generator-cli.jar generate -i /path/to/openapi.json -o /tmp/Lichess -g cpp-qt-client
• cd /tmp/Lichess/client
• mkdir build && cd build
• cmake ..
• make

Related issues/PRs

No existing ones.

Suggest a fix

Proposed fix: https://github.com/OpenAPITools/openapi-generator/pull/19859

The issue identifies the cpp-qt-client generator and the generated client build as entry points. Start by running the listed OpenAPI Generator command with lichess openapi.json, then configure and build the generated client; done is a generated client that compiles without the missing-variable error.