[elm] Add lsp support

layers/+lang/elm/README.org

@@ -13,8 +13,13 @@
     - [[#macos-and-windows-installers][macOS and Windows installers]]
     - [[#universal-installer-using-npm][Universal installer using npm]]
     - [[#source-code][Source code]]
-  - [[#elm-oracle][elm-oracle]]
   - [[#elm-format][elm-format]]
+  - [[#elm-test][elm-test]]
+- [[#configuration][Configuration]]
+  - [[#choosing-a-backend][Choosing a backend]]
+    - [[#company-elm][Company-elm]]
+      - [[#elm-oracle][elm-oracle]]
+    - [[#lsp][LSP]]
 - [[#basic-usage-tips][Basic usage tips]]
   - [[#compilation][Compilation]]
   - [[#reactor][Reactor]]
@@ -42,8 +47,7 @@ It relies on [[https://github.com/jcollard/elm-mode][elm-mode]] and [[https://gi
 ** Features:
 - Syntax highlighting.
 - Intelligent indentation
-- Auto-completion integration for company (default) or auto-complete modes,
-  with using elm-oracle
+- Auto-completion integration for company (default) or auto-complete modes
 - Syntax checking support using flycheck
 - Integration with elm-make
 - Integration with elm-repl
@@ -88,7 +92,55 @@ run, see this issue [[https://github.com/kevva/elm-bin/issues/28][https://github
 To build from source, see instructions here:
 [[https://github.com/elm-lang/elm-platform][https://github.com/elm-lang/elm-platform]]
 
-** elm-oracle
+** elm-format
+=elm-format= can be used to format elm code according to a standard set of
+rules.
+
+To install =elm-format= run below command:
+
+#+BEGIN_SRC sh
+  npm install --global elm-format
+#+END_SRC
+
+If this does not work for you please check [[https://github.com/avh4/elm-format][here]].
+
+Also, note that if you use homebrew to install =elm-format= the installed exe
+has a version suffix, the installed command name can be set in your
+=~/spacemacs=:
+
+#+BEGIN_SRC emacs-lisp
+  (elm :variables
+       elm-format-command "elm-format-0.17")
+#+END_SRC
+
+** elm-test
+=elm-test= can be used to run unit tests.
+
+To install =elm-test= run below command:
+
+#+BEGIN_SRC sh
+  npm install --global elm-test
+#+END_SRC
+
+* Configuration
+All layer configurations can be done by setting layer variables in your dotfile.
+No custom user config lines are necessary
+
+** Choosing a backend
+This layer provides two alternative backends to choose from.
+
+*** Company-elm
+This is the default choice if nothing is set and no lsp layer
+is loaded in your dotfile. This mode only provides very
+limited IDE capabilities. Used best if only small programs
+are edited. To set explicitly set the following in your
+dotfile:
+
+#+BEGIN_SRC emacs-lisp
+  (elm :variables elm-backend 'company-elm)
+#+END_SRC
+
+**** elm-oracle
 =elm-oracle= can be used to show type signatures and docs for tokens under the
 cursor and provide support for auto-completion, but it is not part of the
 standard elm-platform.
@@ -103,22 +155,33 @@ run this command:
   npm install -g elm-oracle
 #+END_SRC
 
-** elm-format
-=elm-format= can be used to format elm code according to a standard set of
-rules.
+*** LSP
+For proper IDE support this backend should be used. It is
+based on an external server which will be started automatically
+by emacs, once an elm file is opened. The key bindings are
+the same for all lsp modes so if you are already familiar with
+one you should be able to work the same in all modes.
 
-To install =elm-format= follow the instructions for the version of elm
-installed: [[https://github.com/avh4/elm-format]]
-
-Also, note that if you use homebrew to install =elm-format= the installed exe
-has a version suffix, the installed command name can be set in your
-=~/spacemacs=:
+To set explicitly do the following in your dotfile:
 
 #+BEGIN_SRC emacs-lisp
   (elm :variables
-       elm-format-command "elm-format-0.17")
+          elm-backend 'lsp)
 #+END_SRC
 
+For this to work you will also need to install
+the lsp server and separate dependencies with below
+command:
+
+#+BEGIN_SRC sh
+  npm install -g elm-analysis @elm-tooling/elm-language-server
+#+END_SRC
+
+NOTE: Key bindings for LSP are defined in the
+LSP layer. Also it is advisable to have a look
+at the autocomplete layer for an optimal
+intellisense config for LSP.
+
 * Basic usage tips
 ** Compilation
 To control the name of the compiled JavaScript file, use ~SPC m c B~ instead of

layers/+lang/elm/config.el

@@ -0,0 +1,19 @@
+;;; config.el --- Elm Layer packages File for Spacemacs
+;;
+;; Copyright (c) 2012-2020 Sylvain Benner & Contributors
+;;
+;; Author: Maximilian Wolff <smile13241324@gmail.com>
+;; URL: https://github.com/syl20bnr/spacemacs
+;;
+;; This file is not part of GNU Emacs.
+;;
+;;; License: GPLv3
+
+;; variables
+
+(spacemacs|define-jump-handlers elm-mode)
+
+(defvar elm-backend nil
+  "The backend to use for IDE features.
+Possible values are `lsp' and `company-elm'.
+If `nil' then 'company-elm` is the default backend unless `lsp' layer is used")

layers/+lang/elm/funcs.el

@@ -1,6 +1,6 @@
 ;;; funcs.el --- Elm Layer functions File for Spacemacs
 ;;
-;; Copyright (c) 2012-2018 Sylvain Benner & Contributors
+;; Copyright (c) 2012-2020 Sylvain Benner & Contributors
 ;;
 ;; Author: Sylvain Benner <sylvain.benner@gmail.com>
 ;; URL: https://github.com/syl20bnr/spacemacs
@@ -9,9 +9,41 @@
 ;;
 ;;; License: GPLv3
 
+(defun spacemacs//elm-backend ()
+  "Returns selected backend."
+  (if elm-backend
+      elm-backend
+    (cond
+     ((configuration-layer/layer-used-p 'lsp) 'lsp)
+     (t 'company-elm))))
+
+(defun spacemacs//elm-setup-company ()
+  "Conditionally setup company based on backend."
+  (pcase (spacemacs//elm-backend)
+    ;; Activate lsp company explicitly to activate
+    ;; standard backends as well
+    (`lsp (spacemacs|add-company-backends
+            :backends company-capf
+            :modes elm-mode))
+    (`company-elm (spacemacs|add-company-backends
+                    :backends elm-company
+                    :modes elm-mode))))
+
+(defun spacemacs//elm-setup-backend ()
+  "Conditionally setup elm backend."
+  (spacemacs/init-elm-mode)
+  (pcase (spacemacs//elm-backend)
+    (`lsp (lsp))
+    (`company-elm (elm-oracle-setup-completion))))
+
 
 ;; elm-mode
 
+(defun spacemacs/init-elm-mode ()
+  "Disable electric-indent-mode and let indentation cycling feature work"
+  (if (fboundp 'electric-indent-local-mode)
+      (electric-indent-local-mode -1)))
+
 (defun spacemacs/elm-compile-buffer-output ()
   (interactive)
   (let* ((fname (format "%s.js" (downcase (file-name-base (buffer-file-name))))))

layers/+lang/elm/layers.el

@@ -0,0 +1,14 @@
+;;; layers.el --- Elm Layer layers File for Spacemacs
+;;
+;; Copyright (c) 2012-2020 Sylvain Benner & Contributors
+;;
+;; Author: Maximilian Wolff <smile13241324@gmail.com>
+;; URL: https://github.com/syl20bnr/spacemacs
+;;
+;; This file is not part of GNU Emacs.
+;;
+;;; License: GPLv3
+
+(when (and (boundp 'elm-backend)
+           (eq elm-backend 'lsp))
+  (configuration-layer/declare-layer-dependencies '(lsp)))

layers/+lang/elm/packages.el

@@ -1,6 +1,6 @@
 ;;; packages.el --- elm Layer packages File for Spacemacs
 ;;
-;; Copyright (c) 2012-2018 Sylvain Benner & Contributors
+;; Copyright (c) 2012-2020 Sylvain Benner & Contributors
 ;;
 ;; Author: Sylvain Benner <sylvain.benner@gmail.com>
 ;; URL: https://github.com/syl20bnr/spacemacs
@@ -9,23 +9,21 @@
 ;;
 ;;; License: GPLv3
 
-(setq elm-packages
-    '(
-      company
-      elm-mode
-      elm-test-runner
-      flycheck
-      (flycheck-elm :requires flycheck)
-      popwin
-      smartparens
-      ))
+(defconst elm-packages
+  '(
+    company
+    elm-mode
+    elm-test-runner
+    flycheck
+    (flycheck-elm :requires flycheck)
+    popwin
+    smartparens))
 
 (defun elm/post-init-company ()
-  (spacemacs|add-company-backends :backends company-elm :modes elm-mode)
-  (add-hook 'elm-mode-hook 'elm-oracle-setup-completion))
+  (spacemacs//elm-setup-company))
 
 (defun elm/post-init-flycheck ()
-  (add-hook 'elm-mode-hook 'flycheck-mode))
+  (spacemacs/enable-flycheck 'elm-mode))
 
 (defun elm/init-flycheck-elm ()
   "Initialize flycheck-elm"
@@ -37,28 +35,31 @@
   "Initialize elm-mode"
   (use-package elm-mode
     :mode ("\\.elm\\'" . elm-mode)
+    :defer t
     :init
     (progn
       (spacemacs/register-repl 'elm-mode 'elm-repl-load "elm")
-
-      (defun spacemacs/init-elm-mode ()
-        "Disable electric-indent-mode and let indentation cycling feature work"
-        (if (fboundp 'electric-indent-local-mode)
-            (electric-indent-local-mode -1)))
-
-      (add-hook 'elm-mode-hook 'spacemacs/init-elm-mode))
+      (add-hook 'elm-mode-hook 'spacemacs//elm-setup-backend))
     :config
     (progn
+      ;; Bind non-lsp keys
+      (when (eq (spacemacs//elm-backend) 'company-elm)
+        (spacemacs/set-leader-keys-for-major-mode 'elm-mode
+          ;; format
+          "=b" 'elm-format-buffer
+          ;; oracle
+          "hh" 'elm-oracle-doc-at-point
+          "ht" 'elm-oracle-type-at-point)
+
+        ;; Bind prefixes
+        (dolist (x '(("m=" . "format")
+                     ("mh" . "help")
+                     ("mg" . "goto")
+                     ("mr" . "refactor")))
+          (spacemacs/declare-prefix-for-mode 'elm-mode (car x) (cdr x))))
+
+      ;; Bind general keys
       (spacemacs/set-leader-keys-for-major-mode 'elm-mode
-        ;; format
-        "=b" 'elm-mode-format-buffer
-        ;; make
-        "cb" 'elm-compile-buffer
-        "cB" 'spacemacs/elm-compile-buffer-output
-        "cm" 'elm-compile-main
-        ;; oracle
-        "hh" 'elm-oracle-doc-at-point
-        "ht" 'elm-oracle-type-at-point
         ;; refactoring
         "ri" 'elm-sort-imports
         ;; repl
@@ -68,6 +69,10 @@
         "sF" 'spacemacs/elm-repl-push-decl-focus
         "sr" 'elm-repl-push
         "sR" 'spacemacs/elm-repl-push-focus
+        ;; make
+        "cb" 'elm-compile-buffer
+        "cB" 'spacemacs/elm-compile-buffer-output
+        "cm" 'elm-compile-main
         ;; reactor
         "Rn" 'elm-preview-buffer
         "Rm" 'elm-preview-main
@@ -76,12 +81,10 @@
         "pc" 'elm-package-catalog
         "pd" 'elm-documentation-lookup)
 
-      (dolist (x '(("m=" . "format")
+      ;; Bind prefixes
+      (dolist (x '(("mp" . "package")
                    ("mc" . "compile")
-                   ("mh" . "help")
-                   ("mp" . "package")
                    ("mR" . "reactor")
-                   ("mr" . "refactor")
                    ("ms" . "repl")))
         (spacemacs/declare-prefix-for-mode 'elm-mode (car x) (cdr x)))
 
@@ -105,8 +108,7 @@
         "tp" 'elm-test-runner-run-project
         "tr" 'elm-test-runner-rerun
         "tw" 'elm-test-runner-watch
-        "t TAB" 'elm-test-runner-toggle-test-and-target
-        ))))
+        "t TAB" 'elm-test-runner-toggle-test-and-target))))
 
 (defun elm/pre-init-popwin ()
   (spacemacs|use-package-add-hook popwin