Revise dart layer

I have:
- Revised the documentation to be more clear about the possible backends
- Simplified the lsp setup code
- Removed redundant loading of company-lsp (is done by lsp-mode already)
- Made lsp the default backend for dart and mentioned that the analyser is
deprecated

CHANGELOG.develop

@@ -1533,7 +1533,7 @@ Other:
   - Fixed =d-mode= flycheck imports on dub projects (thanks to Dietrich Daroch)
 **** Dart
 - Improvements:
-  - Added =LSP= support (thanks to Mathieu Post)
+  - Added =LSP= support (thanks to Mathieu Post and Takeshi Tsukamoto)
   - Added =Flutter= support (thanks to Mathieu Post)
 - Fixes:
   - Added =dart-server= package (thanks to duianto)

layers/+lang/dart/README.org

@@ -43,11 +43,11 @@ To choose a default backend set the layer variable =dart-backend=:
 
 #+BEGIN_SRC elisp
   (setq-default dotspacemacs-configuration-layers '(
-    (dart :variables dart-backend 'analyzer)))
+    (dart :variables dart-backend 'lsp)))
 #+END_SRC
 
-Alternatively the =lsp= backend will be automatically chosen if the layer =lsp=
-is used and you did not specify any value for =dart-backend=.
+Alternatively the =lsp= backend will be automatically chosen if
+you did not specify any value for =dart-backend=.
 
 Backend can be chosen on a per project basis using directory local variables
 (files named =.dir-locals.el= at the root of a project), an example to use the
@@ -60,7 +60,27 @@ Backend can be chosen on a per project basis using directory local variables
 #+END_SRC
 
 * Backends
-** Dart analyzer
+** LSP
+This is the recommended backend it is a full IDE server using the standard
+language server protocol to communicate with emacs.
+
+Current versions of the dart-sdk ship with lsp support directly integrated in
+the =dart-server=. You do not need to worry about starting and stopping the
+server this will be done by spacemacs automatically.
+
+However to get all features make sure that you also load the
+auto-completion and syntax-checking layer in your dotfile.
+
+Emacs will look in the standard SDK location for the lsp server.
+If this is not working for you, please set the custom path via =lsp-dart-sdk-dir=.
+
+#+BEGIN_SRC elisp
+  (dart :variables lsp-dart-sdk-dir "~/path/to/dart-sdk/")
+#+END_SRC
+
+** Dart analyzer (deprecated)
+This backend is not longer officially supported from [[https://github.com/bradyt/dart-server][dart-server]] use the LSP backend instead.
+
 Dart analyzer supported via [[https://github.com/bradyt/dart-server][dart-server]]. You need to enable =dart-server-enable-analysis-server=
 to use analyzer features.
 
@@ -69,8 +89,7 @@ to use analyzer features.
 #+end_src
 
 [[https://github.com/bradyt/dart-server][dart-server]] will use the =dart= executable location if available on the
-execution path, but it is possible to define the location manually. It should
-point to the folder, and end with =/=.
+path, but it is possible to define the location manually. It should point to the folder and end with =/=.
 
 #+BEGIN_SRC elisp
   (dart :variables dart-server-sdk-path "~/path/to/dart-sdk/")
@@ -91,19 +110,6 @@ integration tools.
 
 For additional variables check the [[https://github.com/bradyt/dart-server][dart-server]] documentation.
 
-** LSP
-You must add lsp to the existing dotspacemacs-configuration-layers in your ~/.spacemacs.
-
-Consult the installation command for the desired language server found at lsp-mode for instructions.
-
-To enable auto-completion, ensure that the auto-completion layer is enabled.
-
-If you want to use custom dart sdk location, set it to =lsp-dart-sdk-dir=.
-
-#+BEGIN_SRC elisp
-  (dart :variables lsp-dart-sdk-dir "~/path/to/dart-sdk/")
-#+END_SRC
-
 * Key bindings
 ** Normal mode
 Some of the commands will instantiate a new Dart Analyzer server if necessary,

layers/+lang/dart/config.el

@@ -10,10 +10,8 @@
 ;;; License: GPLv3
 
 ;; Variables
-
-(defvar dart-backend nil
-  "The backend to use for IDE features.
-Possible values are `analyzer' `lsp'.
-If `nil' then `analyzer' is the default backend unless `lsp' layer is used.")
-
 (spacemacs|define-jump-handlers dart-mode)
+
+(defvar dart-backend 'lsp
+  "The backend to use for IDE features.
+Possible values are `analyzer' and `lsp'.")

layers/+lang/dart/funcs.el

@@ -12,46 +12,7 @@
 
 ;; backend
 
-(defun spacemacs//dart-backend ()
-  "Returns selected backend."
-  (if dart-backend
-      dart-backend
-    (cond
-     ((configuration-layer/layer-used-p 'lsp) 'lsp)
-     (t 'analyzer))))
-
 (defun spacemacs//dart-setup-backend ()
-  (pcase (spacemacs//dart-backend)
-    (`analyzer (spacemacs//dart-setup-analyzer))
-    (`lsp (spacemacs//dart-setup-lsp))))
-
-(defun spacemacs//dart-setup-company ()
-  (pcase (spacemacs//dart-backend)
-    (`lsp (spacemacs//dart-setup-company-lsp))))
-
-
-;; analyzer
-
-(defun spacemacs//dart-setup-analyzer ()
-  (dart-server))
-
-
-;; lsp
-
-(defun spacemacs//dart-setup-lsp ()
-  "Setup lsp backend"
-  (if (configuration-layer/layer-used-p 'lsp)
-      (lsp)
-    (message "`lsp' layer is not installed, please add `lsp' layer to your dotfile.")))
-
-(defun spacemacs//dart-setup-company-lsp ()
-  "Setup lsp auto-completion"
-  (if (configuration-layer/layer-used-p 'lsp)
-      (progn
-        (spacemacs|add-company-backends
-          :backends company-lsp
-          :modes dart-mode
-          :append-hooks nil
-          :call-hooks t)
-        (company-mode))
-    (message "`lsp' layer is not installed, please add `lsp' layer to your dotfile.")))
+  (pcase dart-backend
+    (`analyzer (dart-server))
+    (`lsp (lsp))))

layers/+lang/dart/packages.el

@@ -1,6 +1,6 @@
 ;;; packages.el --- dart layer packages file for Spacemacs.
 ;;
-;; Copyright (c) 2012-2018 Sylvain Benner & Contributors
+;; Copyright (c) 2012-2019 Sylvain Benner & Contributors
 ;;
 ;; Author: Bruno Tavares <connect+spacemacs@bltavares.com>
 ;; URL: https://github.com/syl20bnr/spacemacs
@@ -9,14 +9,11 @@
 ;;
 ;;; License: GPLv3
 
-;;; Code:
-
 (defconst dart-packages
   '(
     dart-mode
-    dart-server
-    company
-    flutter
+    (dart-server :toggle (eq dart-backend 'analyzer))
+    (flutter (eq dart-backend 'analyzer))
     flycheck
     ))
 
@@ -78,10 +75,5 @@
       (spacemacs/set-leader-keys-for-major-mode 'dart-mode
         "xx" 'flutter-run-or-hot-reload))))
 
-(defun dart/post-init-company ()
-  (add-hook 'dart-mode-local-vars-hook #'spacemacs//dart-setup-company))
-
 (defun dart/post-init-flycheck ()
   (spacemacs/enable-flycheck 'dart-mode))
-
-;;; packages.el ends here