Conal Elliott
It appears that use of GHC plugins causes client code to get needlessly recompiled. (See Trac issues 12567 https://ghc.haskell.org/trac/ghc/ticket/12567 and 7414 https://ghc.haskell.org/trac/ghc/ticket/7414.) It’s becoming more of a problem for usability of the plugin http://conal.net/papers/compiling-to-categories I’ve been developing, and I’m wondering what can be done. Some questions:
- Is there any work in progress on fixing this situation? - Are there serious obstacles to fixing it? - Do plugin writers or users have any workarounds?
I think the real question is what sort of interface do plugin authors need? I suspect there are a few distinct tasks here, * compute and record module implementation hashes in interface files * to include plugin implementation hashes in the recompilation check * to provide an interface allowing a plugin to compute a hash of its arguments which can be included into the recompilation check. One way of realising this would be to add a field like the following to Plugin, pluginHash :: [CommandLineOption] -> Maybe Fingerprint -- Nothing would denote "always rebuild" Would this help in your case? This would allow us to fix the TH problem in #7277 and fix the plugins problem in #7414 and #12567 in a nearly optimal way (assuming the plugin author is able to precisely define a hash). None of this is terribly difficult and given Nick's recent work on his row types plugin, it seems like it's getting more urgent. Cheers, - Ben