[darcs-devel] developing darcs with an IDE: hie-core

[Ganesh Sittampalam]

Hi,

At Munihac, I've been playing with developing darcs with hie-core:

https://github.com/digital-asset/daml/tree/master/compiler/hie-core

https://www.reddit.com/r/haskell/comments/d0frl8/neil_mitchell_making_a_haskell_ide_munihac_2019/

After making a couple of fixes (which are now released), it's working
pretty well for me, with Visual Studio Code. It's making a significant
difference to my development workflow, particularly being able to get
even more immediate/local feedback on errors than with ghcid which was
my previous workflow.

There are also emacs and vim plugins though I have no experience of them
myself.

I just created a hie.yaml file in the root of my darcs folder, with this
content:

   cradle: {cabal: {component: "lib:darcs"}}

Some gotchas:

 - You can only work with the library or the test harness at one time
(like with cabal v2-repl) - change the hie.yaml to point to
"test:darcs-test" to work on the harness instead.
 - You only get errors in files that are open or their dependencies. For
now I'm just keeping Darcs.UI.TheCommands open so I see most things.
 - You need to open the darcs folder in VS Code, not just a single file.
 - You need to use GHC 8.6 (or perhaps GHC 8.4 soon)

Overall hie-core is still a bit bleeding-edge, but remarkably usable
despite that once you get over a bit of initial setup cost. In
particular the workflow of iterating to make sure that the "hie-core"
command works ok on the command-line made it very easy to debug most
problems outside the IDE.

I'm happy to help anyone who wants to give it a try.

Cheers,

Ganesh