I’m trying to add some custom source code to an engine plugin (MassAI), but I get the “cannot open source file xxx.generated.h” error.
After some search it seems to me that rebuilding the solution will not automatically rebuild the engine plugin, so the “xxx.generated.h” was never generated.
I’m wondering what would be the best way to do this. Rebuild the engine? I don’t know if it will lead to any undesirable side effects, or if it’s really worth it since I’m only making some small changes. Is it possible to rebuild this engine plugin only?
Any suggestion is appreciated!
I have never tried to duplicate an engine plugin myself, but making you own you create a c++ project. Inside of it you add a “Plugin” folder and inside of that you create a folder for with your plugin name.
Copy all of the source files of the plugin into that folder and try recompiling your project.
In theory it should work unless unreal has a problem with duplicate plugin names.
You are supposed to be able to copy engine plugins to your project, make changes and maintain that copy of the plugin until you don’t need it. I’ve never done it myself, but I seen it discussed enough that I’ll repeat it here.
However, the danger is that if you do that you (from what I understand) also have to do the same thing for any engine plugins that depend on the plugin that you’re modifying. Even if you don’t plan on modifying them. The reason for this is that the Engine can’t allow for two plugins (yours and the Engine’s) to coexist in a way that your modules use yours and the Engine modules use the original. Depending on the plugin you’re moving it could be more or less painful.
The alternative is to switch over to a source build of the Engine. Grab everything and compile the entire Engine yourself. This can take a while up front (and when new versions release) but you can change/fix anything in the whole codebase without having to make duplicates. You can even fix things that aren’t in plugins!
You can absolutely just copy an engine plugin into your C++ project’s Plugins folder, and simply delete that plugin from the engine plugins folder. Everything will work as expected, no need to move / modify other plugins. I usually zip up the original plugin so that I can basically reset it at any time.
I’m not sure what you’re experience is with it, but that fundamentally shouldn’t work. Plenty of other people run into problems like this one by doing what you’re suggesting.
Once you have a copy of the plugin in your project, it becomes a project plugin. And Engine plugins can’t depend on project plugins. (and you should start getting build errors like those in the linked post).
Maybe you’ve only modified plugins that don’t have Engine dependencies. There are plenty of those.