plugins always trigger recompilation
When compiling code with a ghc plugin, e.g. ghc -O -fplugin SomePlugin Main.hs, recompilation is triggered for every module. This can make plugins difficult to use in environments with many modules shared between executables.
Since a plugin is a GHC library, I would like to propose that plugin arguments and interface hashes be included in the dependencies for compiled modules, in a similar way to how compiler flags are already included. This would enable ghc to avoid recompilation of modules when using plugins, provided that the plugin and plugin options haven't changed.