python: add support for Language Server Protocol

layers/+lang/python/README.org

@@ -7,8 +7,11 @@
   - [[#features][Features:]]
 - [[#install][Install]]
   - [[#layer][Layer]]
-  - [[#dependencies][Dependencies]]
-    - [[#auto-completion-anaconda-dependencies][Auto-completion: Anaconda dependencies]]
+  - [[#choosing-a-backend][Choosing a backend]]
+- [[#backends][Backends]]
+  - [[#anaconda][Anaconda]]
+  - [[#language-server-protocol][Language Server Protocol]]
+- [[#additional-tools][Additional tools]]
     - [[#syntax-checking][Syntax checking]]
   - [[#test-runner][Test runner]]
   - [[#automatic-buffer-formatting-on-save][Automatic buffer formatting on save]]
@@ -37,9 +40,12 @@
 This layer adds support for the Python language.
 
 ** Features:
-- Auto-completion using [[https://github.com/proofit404/anaconda-mode][anaconda-mode]]
-- Code Navigation using  [[https://github.com/proofit404/anaconda-mode][anaconda-mode]]
-- Documentation Lookup using  [[https://github.com/proofit404/anaconda-mode][anaconda-mode]]  and [[https://github.com/tsgates/pylookup][pylookup]]
+- Support for the following backends:
+  - [[https://github.com/proofit404/anaconda-mode][anaconda]] (default),
+  - [[https://github.com/emacs-lsp/lsp-python][Language Server Protocol]] (experimental),
+- Auto-completion
+- Code Navigation
+- Documentation Lookup using  [[https://github.com/proofit404/anaconda-mode][anaconda-mode]] and [[https://github.com/tsgates/pylookup][pylookup]]
 - Test Runners using [[https://github.com/syl20bnr/nose.el][nose.el]] or [[https://github.com/ionrock/pytest-el][pytest]]
 - Virtual Environment using  [[https://github.com/jorgenschaefer/pyvenv][pyvenv]] and [[https://github.com/yyuu/pyenv][pyenv]]
 - semantic mode is enabled
@@ -57,8 +63,28 @@ To use this configuration layer, add it to your =~/.spacemacs=. You will need to
 add =python= to the existing =dotspacemacs-configuration-layers= list in this
 file.
 
-** Dependencies
-*** Auto-completion: Anaconda dependencies
+** Choosing a backend
+To choose a default backend set the layer variable =python-backend=:
+
+#+BEGIN_SRC elisp
+(python :variables python-backend 'anaconda)
+#+END_SRC
+
+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
+=lsp= backend:
+
+#+BEGIN_SRC elisp
+;;; Directory Local Variables
+;;; For more information see (info "(emacs) Directory Variables")
+
+((python-mode (python-backend . lsp)))
+#+END_SRC
+
+*Note:* you can easily add a directory local variable with ~SPC f v d~.
+
+* Backends
+** Anaconda
 =anaconda-mode= tries to install the dependencies itself but sometimes
 it does not work and you may encounter the following message when
 opening a python buffer:
@@ -82,6 +108,23 @@ If you are facing errors such as "Unable to run anaconda-mode server", try
 setting your =PYTHONPATH= as explained at
 https://github.com/proofit404/anaconda-mode#pythonpath
 
+** Language Server Protocol
+You just have to install python language server package:
+
+#+begin_src sh
+pip install python-language-server
+#+end_src
+
+Additionally you can install the following other packages:
+
+#+begin_src sh
+# for import sorting
+pip install pyls-isort
+# for mypy checking (python 3.4+ is needed)
+pip install pyls-mypy
+#+end_src
+
+* Additional tools
 *** Syntax checking
 Syntax checking uses =flake8= package:
 

layers/+lang/python/config.el

@@ -14,6 +14,10 @@
 (spacemacs|define-jump-handlers python-mode)
 (spacemacs|define-jump-handlers cython-mode anaconda-mode-goto)
 
+(defvar python-backend 'anaconda
+  "The backend to use for IDE features. Possible values are `anaconda'
+and `lsp'.")
+
 (defvar python-enable-yapf-format-on-save nil
   "If non-nil, automatically format code with YAPF on save.")
 

layers/+lang/python/funcs.el

@@ -9,6 +9,82 @@
 ;;
 ;;; License: GPLv3
 
+(defun spacemacs//python-setup-backend ()
+  "Conditionally setup python backend."
+  (pcase python-backend
+    (`anaconda (spacemacs//python-setup-anaconda))
+    (`lsp (spacemacs//python-setup-lsp))))
+
+(defun spacemacs//python-setup-company ()
+  "Conditionally setup company based on backend."
+  (pcase python-backend
+    (`anaconda (spacemacs//python-setup-anaconda-company))
+    (`lsp (spacemacs//python-setup-lsp-company))))
+
+(defun spacemacs//python-setup-eldoc ()
+  "Conditionally setup eldoc based on backend."
+  (pcase python-backend
+    ;; lsp setup eldoc on its own
+    (`anaconda (spacemacs//python-setup-anaconda-eldoc))))
+
+
+;; anaconda
+
+(defun spacemacs//python-setup-anaconda ()
+  "Setup anaconda backend."
+  (anaconda-mode)
+  (add-to-list 'spacemacs-jump-handlers-python-mode
+               '(anaconda-mode-find-definitions :async t)))
+
+(defun spacemacs//python-setup-anaconda-company ()
+  "Setup anaconda auto-completion."
+  (spacemacs|add-company-backends
+    :backends company-anaconda
+    :modes python-mode)
+  (company-mode))
+
+(defun spacemacs//python-setup-anaconda-eldoc ()
+  "Setup anaconda eldoc."
+  (eldoc-mode)
+  (when (configuration-layer/package-used-p 'anaconda-mode)
+    (anaconda-eldoc-mode)))
+
+(defun spacemacs/anaconda-view-forward-and-push ()
+  "Find next button and hit RET"
+  (interactive)
+  (forward-button 1)
+  (call-interactively #'push-button))
+
+(defun spacemacs//disable-semantic-idle-summary-mode ()
+  "Disable semantic-idle-summary in Python mode.
+Anaconda provides more useful information but can not do it properly
+when this mode is enabled since the minibuffer is cleared all the time."
+  (semantic-idle-summary-mode 0))
+
+
+;; lsp
+
+(defun spacemacs//python-setup-lsp ()
+  "Setup lsp backend."
+  (if (configuration-layer/layer-used-p 'lsp)
+      (progn
+        (require 'lsp-python)
+        (lsp-python-enable))
+    (message "`lsp' layer is not installed, please add `lsp' layer to your dofile.")))
+
+(defun spacemacs//python-setup-lsp-company ()
+  "Setup lsp auto-completion."
+  (if (configuration-layer/layer-used-p 'lsp)
+      (progn
+        (spacemacs|add-company-backends
+          :backends company-lsp
+          :modes python-mode)
+        (company-mode))
+    (message "`lsp' layer is not installed, please add `lsp' layer to your dofile.")))
+
+
+;; others
+
 (defun spacemacs//python-default ()
   "Defaut settings for python buffers"
   (setq mode-name "Python"
@@ -138,12 +214,6 @@ as the pyenv version then also return nil. This works around https://github.com/
 
 ;; Tests
 
-(defun spacemacs//disable-semantic-idle-summary-mode ()
-  "Disable semantic-idle-summary in Python mode.
-Anaconda provides more useful information but can not do it properly
-when this mode is enabled since the minibuffer is cleared all the time."
-  (semantic-idle-summary-mode 0))
-
 (defun spacemacs//python-imenu-create-index-use-semantic-maybe ()
   "Use semantic if the layer is enabled."
   (setq imenu-create-index-function 'spacemacs/python-imenu-create-index))
@@ -251,14 +321,6 @@ to be called for each testrunner. "
              (derived-mode-p 'python-mode))
     (py-isort-before-save)))
 
-
-;;* Anaconda
-(defun spacemacs/anaconda-view-forward-and-push ()
-  "Find next button and hit RET"
-  (interactive)
-  (forward-button 1)
-  (call-interactively #'push-button))
-
 
 ;; REPL
 
@@ -336,11 +398,3 @@ to be called for each testrunner. "
   (advice-add 'wisent-python-default-setup :after
               #'spacemacs//python-imenu-create-index-use-semantic-maybe))
 
-
-;; Eldoc
-
-(defun spacemacs//init-eldoc-python-mode ()
-  "Initialize elddoc for python buffers"
-  (eldoc-mode)
-  (when (configuration-layer/package-used-p 'anaconda-mode)
-    (anaconda-eldoc-mode)))

layers/+lang/python/packages.el

@@ -26,6 +26,7 @@
     hy-mode
     importmagic
     live-py-mode
+    (lsp-python :requires lsp-mode)
     (nose :location local)
     org
     pip-requirements
@@ -46,13 +47,8 @@
 (defun python/init-anaconda-mode ()
   (use-package anaconda-mode
     :defer t
-    :init
-    (progn
-      (setq anaconda-mode-installation-directory
-            (concat spacemacs-cache-directory "anaconda-mode"))
-      (add-hook 'python-mode-hook 'anaconda-mode)
-      (add-to-list 'spacemacs-jump-handlers-python-mode
-                '(anaconda-mode-find-definitions :async t)))
+    :init (setq anaconda-mode-installation-directory
+                (concat spacemacs-cache-directory "anaconda-mode"))
     :config
     (progn
       (spacemacs/set-leader-keys-for-major-mode 'python-mode
@@ -75,6 +71,8 @@
         (evil--jumps-push)))))
 
 (defun python/post-init-company ()
+  ;; backend specific
+  (add-hook 'python-mode-local-vars-hook #'spacemacs//python-setup-company)
   (spacemacs|add-company-backends
     :backends (company-files company-capf)
     :modes inferior-python-mode
@@ -89,9 +87,8 @@
 (defun python/init-company-anaconda ()
   (use-package company-anaconda
     :defer t
-    :init (spacemacs|add-company-backends
-            :backends company-anaconda
-            :modes python-mode)))
+    ;; see `spacemacs//python-setup-anaconda-company'
+    ))
 
 (defun python/init-cython-mode ()
   (use-package cython-mode
@@ -103,7 +100,7 @@
         "gu" 'anaconda-mode-find-references))))
 
 (defun python/post-init-eldoc ()
-  (add-hook 'python-mode-hook 'spacemacs//init-eldoc-python-mode))
+  (add-hook 'python-mode-local-vars-hook #'spacemacs//python-setup-eldoc))
 
 (defun python/post-init-evil-matchit ()
   (add-hook `python-mode-hook `turn-on-evil-matchit-mode))
@@ -164,6 +161,10 @@
     (spacemacs/set-leader-keys-for-major-mode 'python-mode
       "l" 'live-py-mode)))
 
+(defun python/init-lsp-python ()
+  (use-package lsp-python
+    :commands lsp-python-enable))
+
 (defun python/init-nose ()
   (use-package nose
     :commands (nosetests-one
@@ -282,10 +283,13 @@
     :mode (("SConstruct\\'" . python-mode) ("SConscript\\'" . python-mode))
     :init
     (progn
-      (spacemacs/register-repl 'python 'spacemacs/python-start-or-switch-repl "python")
+      (spacemacs/register-repl 'python
+                               'spacemacs/python-start-or-switch-repl "python")
       (add-hook 'inferior-python-mode-hook
-                #'spacemacs//inferior-python-setup-hook)
-      (add-hook 'python-mode-hook #'spacemacs//python-default)
+                'spacemacs//inferior-python-setup-hook)
+      (spacemacs/add-to-hook 'python-mode-hook
+                             '(spacemacs//python-setup-backend
+                               spacemacs//python-default))
       ;; call `spacemacs//python-setup-shell' once, don't put it in a hook
       ;; (see issue #5988)
       (spacemacs//python-setup-shell))