[cmake] Add lsp server support

layers/+tools/cmake/README.org

@@ -8,28 +8,79 @@
 - [[#description][Description]]
   - [[#features][Features:]]
 - [[#install][Install]]
-  - [[#layer][Layer]]
-  - [[#cmake-ide-configuration][CMake-ide configuration]]
+- [[#configuration][Configuration]]
+  - [[#choosing-a-backend][Choosing a backend]]
+    - [[#company-cmake][Company-cmake]]
+    - [[#lsp][LSP]]
+  - [[#cmake-ide][CMake-ide]]
 - [[#key-bindings][Key bindings]]
 
 * Description
 This layer adds support [[https://cmake.org/][CMake]] scripts.
 
 ** Features:
-- Support for CMake configure/build (with limited support for other build systems),
-  automatic generation of =compile_commands.json= (compile flags), on-the-fly configuration
-  of flycheck, company-clang and RTags (if installed) with [[https://github.com/atilaneves/cmake-ide][cmake-ide]].
+- Syntax highlighting
+- Auto-completion
+- Support for CMake configure/build (with limited support for other build systems) and
+  automatic generation of =compile_commands.json= (compile flags).
 - Run selected test using =Helm= interface via =helm-ctest=.
+- Extraction of compile parameters from =compile_commands.json= with [[https://github.com/atilaneves/cmake-ide][cmake-ide]]
 
 * Install
-** Layer
 To use this configuration layer, add it to your =~/.spacemacs=. You will need to
 add =cmake= to the existing =dotspacemacs-configuration-layers= list in this
 file.
 
-** CMake-ide configuration
+* 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-cmake
+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 scripts
+are edited. To set explicitly set the following in your
+dotfile:
+
+#+BEGIN_SRC emacs-lisp
+  (cmake :variables cmake-backend 'company-cmake)
+#+END_SRC
+
+*** 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 a cmake 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 set explicitly do the following in your dotfile:
+
+#+BEGIN_SRC emacs-lisp
+  (cmake :variables
+          cmake-backend 'lsp)
+#+END_SRC
+
+For this to work you will also need to obtain
+the latest version of the lsp server from [[https://github.com/regen100/cmake-language-server][here]].
+
+You can also simply install it with pip:
+
+#+BEGIN_SRC sh
+  pip install cmake-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.
+
+** CMake-ide
+
 To enable CMake projects support set the layer variable =cmake-enable-cmake-ide-support=
-to =t= in the dotfile:
+to =t= in your dotfile:
 
 #+BEGIN_SRC emacs-lisp
   (setq-default dotspacemacs-configuration-layers
@@ -37,8 +88,11 @@ to =t= in the dotfile:
 #+END_SRC
 
 =cmake-ide= plugin has several useful configuration options.
+Normally all should just work well as long as there is a standard
+cmake compilation database available. If not some manual configuration
+may be necessary. Details can be found below.
 
-To configure project you need to create =.dir-locals.el= file. In case of using
+To configure a project you need to create =.dir-locals.el= file. In case of using
 make as CMake backend you can use =helm-make= to select required build target.
 
 Here is a sample configuration. This configuration forces =cmake-ide= to use the

layers/+tools/cmake/config.el

@@ -1,6 +1,6 @@
 ;;; config.el --- CMake layer config file for Spacemacs.
 ;;
-;; Copyright (c) 2018 Sylvain Benner & Contributors
+;; Copyright (c) 2012-2020 Sylvain Benner & Contributors
 ;;
 ;; Author: Alexander Dalshov <dalshov@gmail.com>
 ;; URL: https://github.com/syl20bnr/spacemacs
@@ -16,3 +16,8 @@
 
 (defvar cmake-enable-cmake-ide-support nil
   "If non nil CMake related packages and configuration are enabled.")
+
+(defvar cmake-backend nil
+  "The backend to use for IDE features.
+Possible values are `lsp' and `company-cmake'.
+If `nil' then 'company-cmake` is the default backend unless `lsp' layer is used")

layers/+tools/cmake/funcs.el

@@ -0,0 +1,35 @@
+;;; funcs.el --- CMake Layer functions 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
+
+(defun spacemacs//cmake-backend ()
+  "Returns selected backend."
+  (if cmake-backend
+      cmake-backend
+    (cond
+     ((configuration-layer/layer-used-p 'lsp) 'lsp)
+     (t 'company-cmake))))
+
+(defun spacemacs//cmake-setup-company ()
+  "Conditionally setup company based on backend."
+  (pcase (spacemacs//cmake-backend)
+    ;; Activate lsp company explicitly to activate
+    ;; standard backends as well
+    (`lsp (spacemacs|add-company-backends
+            :backends company-capf
+            :modes cmake-mode))
+    (`company-cmake (spacemacs|add-company-backends
+                      :backends company-cmake
+                      :modes cmake-mode))))
+
+(defun spacemacs//cmake-setup-backend ()
+  "Conditionally setup cmake backend."
+  (pcase (spacemacs//cmake-backend)
+    (`lsp (lsp))))

layers/+tools/cmake/layers.el

@@ -0,0 +1,14 @@
+;;; layers.el --- cmake 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 'cmake-backend)
+           (eq cmake-backend 'lsp))
+  (configuration-layer/declare-layer-dependencies '(lsp)))

layers/+tools/cmake/packages.el

@@ -1,6 +1,6 @@
 ;;; packages.el --- CMake layer packages file for Spacemacs.
 ;;
-;; Copyright (c) 2012-2018 Sylvain Benner & Contributors
+;; Copyright (c) 2012-2020 Sylvain Benner & Contributors
 ;;
 ;; Author: Alexander Dalshov <dalshov@gmail.com>
 ;; URL: https://github.com/syl20bnr/spacemacs
@@ -8,13 +8,12 @@
 ;; This file is not part of GNU Emacs.
 ;;
 ;;; License: GPLv3
-(setq cmake-packages
-      '(
-        cmake-ide
-        cmake-mode
-        company
-        (helm-ctest :requires helm)
-        ))
+(defconst cmake-packages
+  '(
+    (cmake-ide :toggle cmake-enable-cmake-ide-support)
+    cmake-mode
+    company
+    (helm-ctest :requires helm)))
 
 (defun cmake/init-cmake-ide ()
   (use-package cmake-ide
@@ -38,10 +37,11 @@
 (defun cmake/init-cmake-mode ()
   (use-package cmake-mode
     :defer t
-    :mode (("CMakeLists\\.txt\\'" . cmake-mode) ("\\.cmake\\'" . cmake-mode))))
+    :mode (("CMakeLists\\.txt\\'" . cmake-mode) ("\\.cmake\\'" . cmake-mode))
+    :init (add-hook 'cmake-mode-hook #'spacemacs//cmake-setup-backend)))
 
 (defun cmake/post-init-company ()
-  (spacemacs|add-company-backends :backends company-cmake :modes cmake-mode))
+  (spacemacs//cmake-setup-company))
 
 (defun cmake/init-helm-ctest ()
   (use-package helm-ctest