Here are some notes about setting up your Emacs for cardano-wallet development.
General Haskell editing
Start off by applying repo default settings with editorconfig.
(use-package editorconfig
:delight
:config
(editorconfig-mode 1))Since Emacs 26, there is a built-in mode to show the column limit, which you must respect:
(defun rvl/display-fill-column ()
(setq display-fill-column-indicator 1)
(display-fill-column-indicator-mode))
Add some custom font locking to make fixme and TODO things stand out:
(defun rvl/font-lock-keywords ()
"Configure font-lock-mode to highlight TODO/fixme tags"
(font-lock-add-keywords
nil
'(("\\<\\(fixme\\|TODO\\|BUG\\|XXX\\):" 1 font-lock-warning-face t))))Basic Haskell Mode
See the haskell-mode docs for all of the options.
(use-package haskell-mode
:delight "λ"
:after haskell-font-lock
:config
;; Flycheck is usually slow for Haskell stuff - only run on save.
(setq flycheck-check-syntax-automatically '(mode-enabled save))
:init
(defun rvl/enable-subword-mode ()
"Navigate within identifier names"
(subword-mode +1))
(defun rvl/stylish-on-save ()
(setq haskell-stylish-on-save t)
:hook ((haskell-mode . rvl/display-fill-column)
(haskell-mode . rvl/stylish-on-save)
(haskell-mode . rvl/font-lock-keywords)
(haskell-mode . direnv-update-environment)
(haskell-mode . rvl/enable-subword-mode)
(haskell-mode . haskell-indentation-mode)
(haskell-mode . imenu-add-menubar-index))
:bind (:map haskell-mode-map
("C-c C-c" . haskell-process-cabal-build)
("C-c c" . haskell-process-cabal)
("C-c v c" . haskell-cabal-visit-file)
("C-c i" . haskell-navigate-imports)
;; YMMV with haskell-interactive-mode - LSP is a better bet
("C-`" . haskell-interactive-bring)
("C-c C-l" . haskell-process-load-file)
("C-c C-t" . haskell-process-do-type)
("C-c C-i" . haskell-process-do-info)
("C-c C-k" . haskell-interactive-mode-clear)
;; These are usually set by default, but just make sure:
("M-." . xref-find-definitions)
("M-," . xref-pop-marker-stack)
("M-," . xref-find-references)
:map haskell-cabal-mode-map
("C-c C-c" . haskell-process-cabal-build)
("C-c c" . haskell-process-cabal))
:custom
(haskell-process-log t))Haskell Language Server
This is now the best way of getting IDE features.
(use-package lsp-haskell
:after (haskell-mode lsp-mode)
:config
;; Comment/uncomment this line to see interactions between lsp client/server.
;; (setq lsp-log-io t)
:custom
;(lsp-haskell-process-args-hie '("-d" "-l" "/tmp/hie.log"))
;(lsp-haskell-server-args ())
(lsp-haskell-server-path "haskell-language-server"))
(use-package lsp-ui
:after lsp-mode
:commands lsp-ui-mode
:custom
(lsp-ui-peek-enable t)
(lsp-ui-peek-show-directory t)
(lsp-ui-doc-enable t)
;; You might want this:
; (lsp-ui-doc-show-with-cursor nil)
;; Also this because isearch gets broken otherwise
; (lsp-ui-doc-show-with-mouse nil)
(lsp-ui-doc-position 'top)
(lsp-ui-imenu-window-width 20))
(use-package lsp-mode
:commands lsp
:init
;; You need to restart emacs for keymap prefix to take effect
; (setq lsp-keymap-prefix "M-L")
:config
;; so that dir-locals have effect:
;; https://github.com/emacs-lsp/lsp-mode/issues/405
(add-hook 'hack-local-variables-hook (lambda () (when lsp-mode (lsp))))
:hook ((haskell-mode . lsp-deferred)
(haskell-literate-mode . lsp-deferred)
(lsp-managed-mode . lsp-modeline-diagnostics-mode)
;; if you want which-key integration
; (lsp-mode . (lambda () (lsp-enable-which-key-integration t)))
)
:custom
(lsp-progress-via-spinner nil) ;; spinner seems to cause problems
(lsp-restart 'ignore)
(lsp-keep-workspace-alive nil)
(lsp-headerline-breadcrumb-enable t)
(lsp-headerline-breadcrumb-segments '(symbols))
(lsp-lens-enable t)
(lsp-enable-snippet nil)
;; :global/:workspace/:file
(lsp-modeline-diagnostics-scope :workspace)
(lsp-file-watch-threshold 2000)
; (setq lsp-idle-delay 0.500)
(lsp-completion-provider :capf))
(use-package lsp-lens :delight)Performance tweaks
These settings are for reducing emacs-lsp slowness. See lsp-mode Performance for more details.
(setq read-process-output-max (* 1024 1024)) ;; 1mb
(setq gc-cons-threshold 80000000)Flycheck and completion
;; Configure flycheck, but don't enable globally.
(use-package flycheck
:delight
:config
;; set the error window size
(add-to-list 'display-buffer-alist
`(,(rx bos "*Flycheck errors*" eos)
(display-buffer-reuse-window
display-buffer-in-side-window)
(side . bottom)
(reusable-frames . visible)
(window-height . 0.2))))
;; Enable completion globally
(use-package company
:delight
:config
;; company completion everywhere, except where it's annoying.
(add-hook 'after-init-hook 'global-company-mode)
(setq company-global-modes '(not erc-mode))
;; Selectively enable idle popup of completions.
(setq company-idle-delay
(lambda ()
(if (or (bound-and-true-p message-mode) (bound-and-true-p prog-mode))
0.2 nil))))
Direnv support in Emacs
You definitely want direnv support in Emacs if using Nix.
(use-package direnv
:config
;; enable globally
(direnv-mode)
;; exceptions
; (add-to-list 'direnv-non-file-modes 'foobar-mode)
;; nix-shells make too much spam -- hide
(setq direnv-always-show-summary nil)
:hook
;; ensure direnv updates before flycheck and lsp
;; https://github.com/wbolster/emacs-direnv/issues/17
(flycheck-before-syntax-check . direnv-update-environment)
(lsp-before-open-hook . direnv-update-environment)
:custom
;; quieten logging
(warning-suppress-types '((direnv))))nix-direnv for development shells
Now finally, make sure you have nix-direnv installed and enabled for your repo working directories.
Direnv integration will ensure that all build tools in shell.nix are available for Emacs to use. Importantly, this includes haskell-language-server.