Example GHC Plugin

This repository contains an example project to demonstrate that changes in a GHC Plugin do not cause recompilation of modules using the plugin if its added using the addCorePlugin

If a plugin is added using the {-# OPTIONS_GHC -fplugin Plugin #-} pragma then recompilation happens as expected.

Steps to reproduce

1. Building first time triggers plugin when compiling the exe/Main.hs:

cabal build all | grep Hello
--------------- Hello from plugin!

2. Building second time does not (Nothing has changed so no recompilation needed).
3. Changing exe/Main.hs does trigger plugin:

cabal build all | grep Hello
--------------- Hello from plugin!

4. Changing the Plugin (e.g. by modifying a message in the https://github.com/Unisay/plugin-recomp-repro/blob/main/src/Plugin.hs) doesn't trigger recompilation of exe/Main.hs that uses the plugin, so its not triggered:

cabal build all | grep Hello

GHC recompilation avoidance doc.