Add +ghcide flag to lang/haskell

Closes #2622

docs/modules.org

@@ -107,7 +107,7 @@ Modules that bring support for a language or group of languages to Emacs.
 + [[file:../modules/lang/fsharp/README.org][fsharp]] - TODO
 + [[file:../modules/lang/fstar/README.org][fstar]] - F* support
 + [[file:../modules/lang/go/README.org][go]] =+lsp= - TODO
-+ [[file:../modules/lang/haskell/README.org][haskell]] =+dante +intero +lsp= - TODO
++ [[file:../modules/lang/haskell/README.org][haskell]] =+dante +ghcide +lsp +intero= - TODO
 + hy - TODO
 + [[file:../modules/lang/idris/README.org][idris]] - TODO
 + java =+meghanada +lsp= - TODO

modules/lang/haskell/+lsp.el

@@ -1,10 +1,14 @@
 ;;; lang/haskell/+lsp.el -*- lexical-binding: t; -*-
 
 (use-package! lsp-haskell
-  :after haskell-mode
+  :after lsp-clients
-  :init (add-hook 'haskell-mode-hook #'lsp!)
+  :init (add-hook 'haskell-mode-local-vars #'lsp!)
   :config
   (when IS-MAC
     (setq lsp-haskell-process-path-hie "hie-wrapper"))
   ;; Does some strange indentation if it pastes in the snippet
-  (setq-hook! 'haskell-mode-hook yas-indent-line 'fixed))
+  (setq-hook! 'haskell-mode-hook yas-indent-line 'fixed)
+
+  (when (featurep! +ghcide)
+    (setq lsp-haskell-process-path-hie "ghcide"
+          lsp-haskell-process-args-hie nil)))

modules/lang/haskell/README.org

@@ -10,7 +10,8 @@
   - [[#plugins][Plugins]]
 - [[#prerequisites][Prerequisites]]
   - [[#cabal][Cabal]]
-  - [[#lsp][LSP]]
+  - [[#lsp-haskell-ide-engine][LSP (haskell-ide-engine)]]
+  - [[#lsp-ghcide][LSP (ghcide)]]
   - [[#stack][Stack]]
   - [[#haskell-packages][Haskell packages]]
 - [[#configuration][Configuration]]
@@ -18,8 +19,8 @@
 - [[#troubleshooting][Troubleshooting]]
 
 * Description
-This module adds [[https://www.haskell.org/][Haskell]] support, powered by either [[https://github.com/jyp/dante][dante]] (the default), LSP or
+This module adds [[https://www.haskell.org/][Haskell]] support, powered by either [[https://github.com/jyp/dante][dante]] (the default), LSP
-[[https://haskell-lang.org/intero][intero]].
+(haskell-language-server or ghcide) or [[https://haskell-lang.org/intero][intero]].
 
 + Code completion (~company-ghc~)
 + Look up documentation (~hoogle~)
@@ -41,7 +42,9 @@ Here are a few resources I've found indispensable in my Haskell adventures:
 + =+dante= Enables dante; a fork of intero aimed at lightweightedness. It
   doesn't depend on =stack=, supports both ~cabal~-only and ~stack~ projects,
   but lacks eldoc support.
-+ =+lsp= Enables lsp-haskell (this requires the ~:tools lsp~ to be enabled).
++ =+ghcide= Enables LSP support with ghcide (requires the ~:tools lsp~ module).
++ =+lsp= Enables LSP support with haskell-ide-engine (requires the ~:tools lsp~
+  module).
 + =+intero= (Deprecated) Enables intero; a comprehensive, stack-based
   development environment for Haskell.
 
@@ -53,7 +56,7 @@ Here are a few resources I've found indispensable in my Haskell adventures:
 + =+lsp=
   + [[https://github.com/emacs-lsp/lsp-haskell][lsp-haskell]]
 + =+intero=
-  + [[https://github.com/chrisdone/intero][intero]]
+  + [[https://github.com/chrisdone/intero][intero]] =DEPRECATED=
 
 * Prerequisites
 Depending on whether you use Intero, Dante or LSP, your dependencies will
@@ -83,7 +86,7 @@ sudo pacman -S cabal-install ghc
 sudo zypper install cabal-install ghc
 #+END_SRC
 
-** LSP
+** LSP (haskell-ide-engine)
 You will need =stack= and =git= installed.
 
 You will find a comprehensive [[https://github.com/haskell/haskell-ide-engine#installation][install guide for haskell-ide-engine on its
@@ -92,7 +95,7 @@ project page]], but here's a TL;DR:
 *** MacOS
 haskell-ide-engine must be build and installed manually on MacOS, e.g.
 
-#+BEGIN_SRC emacs-lisp
+#+BEGIN_SRC bash
 git clone https://github.com/haskell/haskell-ide-engine
 cd haskell-ide-engine
 make
@@ -101,9 +104,11 @@ make
 *** Arch Linux
 =haskell-ide-engine-git= is available on the AUR
 
-#+BEGIN_SRC emacs-lisp
+#+BEGIN_SRC bash
 yay -S haskell-ide-engine-git
 #+END_SRC
+** LSP (ghcide)
+See https://github.com/digital-asset/ghcide for install instructions.
 
 ** Stack
 To use Intero or LSP, you need =stack=:

modules/lang/haskell/config.el

@@ -3,14 +3,9 @@
 (after! projectile
   (add-to-list 'projectile-project-root-files "stack.yaml"))
 
-;; TODO ghcide?
-(cond ((featurep! +intero) (load! "+intero")) ; DEPRECATED
-      ((featurep! +dante)  (load! "+dante"))
-      ((featurep! +lsp)    (load! "+lsp")))
-
 
 ;;
-;; Common packages
+;;; Common packages
 
 (after! haskell-mode
   (setq haskell-process-suggest-remove-import-lines t  ; warnings for redundant imports etc
@@ -45,3 +40,13 @@
         "c" #'haskell-cabal-visit-file
         "h" #'haskell-hide-toggle
         "H" #'haskell-hide-toggle-all))
+
+
+;;
+;;; Backends
+
+(cond ((featurep! +intero) (load! "+intero")) ; DEPRECATED
+      ((featurep! +dante)  (load! "+dante"))
+      ((or (featurep! +lsp)
+           (featurep! +ghcide))
+       (load! "+lsp")))