Am I right that a plugin forked from ... would need a compiler version of 1.9+? for the project that uses the plugin?
No, you can use any stable compiler to compile plugin itself
But it's better to depend on
kotlin-compiler-embedable
of most recent dev version, because atm compiler API changes quite often (not the extensions API, but compiler internals itself)
Also, for FIR to work in the editor, should I use an EAP IDEA? These are not problems for me, I just want to figure out how to proceed.
There is a prototype of out-of-box plugin support (plugins automatically loaded into IDE from gradle configuration) in K2 IDE plugin. But K2 IDE itself is not avaliable anywhere except
master
IDEA branch. So if you want to play with it you need to build IDEA from sources (there is a prepared
IDEA Community (K2 Kotlin)
run configuration for that. Also you will need to set
kotlin.k2.only.bundled.compiler.plugins.enabled
registry key to
true
in the IDE you built to enable plugins loading (there are not solved questions about binary compatibility, so by default only official plugins are loaded)