[BUG][C++][QT] Unable to compile generated sources from cpp-qt-client generator

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Description

I am using Gitea (version 1.23.4) which provides swagger.json for it's API. I was able to generate code for python, however, when I used cpp-qt-client generator, source code was successful generated, but I am not able to compile it.

CMake is working find, but make ends up with:

[  0%] Built target QtGiteaApi_autogen_timestamp_deps
[  1%] Automatic MOC for target QtGiteaApi
[  1%] Built target QtGiteaApi_autogen
[  1%] Building CXX object CMakeFiles/QtGiteaApi.dir/QtGiteaApi_autogen/mocs_compilation.cpp.o
In file included from /opt/git/test/API_Gitea/cpp_qt/client/build/QtGiteaApi_autogen/EWIEGA46WW/../../../Gitea_AdminApi.h:34,
                 from /opt/git/test/API_Gitea/cpp_qt/client/build/QtGiteaApi_autogen/EWIEGA46WW/moc_Gitea_AdminApi.cpp:10,
                 from /opt/git/test/API_Gitea/cpp_qt/client/build/QtGiteaApi_autogen/mocs_compilation.cpp:3:
/opt/git/test/API_Gitea/cpp_qt/client/build/QtGiteaApi_autogen/EWIEGA46WW/../../../Gitea_Repository.h:560:22: error: field ‘m_parent’ has incomplete type ‘gitea::v1::Gitea_Repository’
  560 |     Gitea_Repository m_parent;
      |                      ^~~~~~~~
/opt/git/test/API_Gitea/cpp_qt/client/build/QtGiteaApi_autogen/EWIEGA46WW/../../../Gitea_Repository.h:45:7: note: definition of ‘class gitea::v1::Gitea_Repository’ is not complete until the closing brace
   45 | class Gitea_Repository : public Gitea_Object {
      |       ^~~~~~~~~~~~~~~~
make[2]: *** [CMakeFiles/QtGiteaApi.dir/build.make:85: CMakeFiles/QtGiteaApi.dir/QtGiteaApi_autogen/mocs_compilation.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:90: CMakeFiles/QtGiteaApi.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

I checked similar issue #6377 which was closed as resolved but I still have same problem, so I opened this issue.

openapi-generator version

7.12.0

OpenAPI declaration file content or url

swagger.json

Generation Details

I am using openapi-generator-cli of version 7.12.0 with cpp-qt-client generator. I am not using any specific config, only command line arguments.

Steps to reproduce

1. generate sources:

   openapi-generator-cli generate -i swagger.v1.json -g cpp-qt-client -o /tmp/gitea_test/ --additional-properties=allowUnicodeIdentifiers=true,cppNamespace=gitea::v1;enumUnknownDefaultCase=true;packageName=QtGiteaApiClient
   

2. create build dir

   cd /tmp/gitea_test/client && mkdir build && cd build
   

3. run cmake:

   cmake ../CMakeLists.txt
   

4. run make
5. Error during compilation occurs.

Related issues/PRs

#6377

Suggest a fix

Reproduce the failure with the linked swagger.json using the cpp-qt-client command, then run CMake and make as described. Inspect the generated Gitea_Repository.h around m_parent and the cpp-qt-client generator sources; done means the generated project compiles successfully without the incomplete-type error.