[Paraview] Question on compiling external plugins with 5.2

[Fabian Wein]

Hello,

we have a legacy implementation of a PV reader plugin which is patched into the PV code.

I want to refactor this approach to an external plugin.

In https://gitlab.kitware.com/paraview/paraview-superbuild it says:
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External plugins
The superbuild supports building more plugins into ParaView using the paraviewexternalplugins project. As an example, to build two external plugins a and b, the following settings should be used:
• enable_paraviewexternalplugins:BOOL=ON: Enables building using external plugins.
• paraview_PLUGINS_EXTERNAL:STRING=a;b: The list of plugins to build.
• paraview_PLUGIN_a_PATH:PATH=/path/to/plugin/a: The path to plugin a's source directory. It must contain a plugins.cmake to be picked up by ParaView.
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Sounds good, I assumed I have to add this via -D to the superbuild cmake, however it tells me
CMake Warning:
  Manually-specified variables were not used by the project:
    enable_paraviewexternalplugins

And indeed I could not find anything about this, not in the code and not with google.

what do I miss? I there somewhere an example or documentation? Is this something new with 5.2?

Thanks for any help,

Fabian