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=lsp-mode= client leveraging Microsoft's [[https://github.com/Microsoft/python-language-server][python-language-server]].

This project is marked as DEPRECATED, since [Microsoft's Python Lang Server](https://github.com/microsoft/python-language-server) has already been archived and is replaced by [pyright](https://github.com/microsoft/pyright). The successor is [lsp-pyright](https://github.com/emacs-lsp/lsp-pyright).

* Installation

Include ~lsp-python-ms~ in the configuration file:
#+BEGIN_SRC emacs-lisp
(require 'lsp-python-ms)
(setq lsp-python-ms-auto-install-server t)
(add-hook 'python-mode-hook #'lsp) ; or lsp-deferred
#+END_SRC

A minimal ~use-package~ initialization might be:
#+BEGIN_SRC elisp
  (use-package lsp-python-ms
    :ensure t
    :init (setq lsp-python-ms-auto-install-server t)
    :hook (python-mode . (lambda ()
                            (require 'lsp-python-ms)
                            (lsp))))  ; or lsp-deferred
#+END_SRC

** Installing the executable

*** NixOS

Building the executable manually is difficult on NixOS, but it can be easily installed via the package manager.
At the time of writing (May 2020), it is not available on the 20.03 release, but can be acquired on the unstable branch.

#+begin_src bash
    nix-channel --add https://nixos.org/channels/nixos-unstable nixos
    nix-channel --update nixos
#+end_src

You can then install the executable by running ~nix-env -iA nixpkgs.python-language-server~
or by adding ~nixpkgs.python-language-server~ to your ~configuration.nix~ and creating a new generation.
Note that ~python37Packages.python-language-server~ refers to Palintir's language server, not Microsoft's.

Finally, ensure that Emacs knows where to find the executable by setting ~lsp-python-ms-executable~.

#+begin_src elisp
  (use-package lsp-python-ms
    :ensure t
    :hook (python-mode . (lambda ()
                           (require 'lsp-python-ms)
                           (lsp)))
    :init
    (setq lsp-python-ms-executable (executable-find "python-language-server")))

#+end_src

*** Most other distros

Normally the [[https://github.com/Microsoft/python-language-server][python-language-server]] will be downloaded automatically if it doesn't
exist while opening the python scripts.

If you have troubles to download the package, you can also build the server yourselves.

1. Install [[https://www.microsoft.com/net/download][dotnet-sdk]]
2. Clone and build [[https://github.com/Microsoft/python-language-server][python-language-server]]:
   #+BEGIN_SRC bash
   git clone https://github.com/Microsoft/python-language-server.git
   cd python-language-server/src/LanguageServer/Impl
   dotnet publish -c Release -r osx-x64   # mac
   #+END_SRC

   Change the ~-r~ flag according to your architecture and operating system.
   See Microsoft's [[https://docs.microsoft.com/en-us/dotnet/core/rid-catalog][Runtime ID Catalog]] for the right value for your system.

   Then make the binary executable.
   #+BEGIN_SRC bash
   chmod a+x $(git rev-parse --show-toplevel)/output/bin/Release/osx-x64/publish/Microsoft.Python.LanguageServer
   #+END_SRC

   NOTE: on some systems (for example, Fedora), the executable comes out as
         ~Microsoft.Python.LanguageServer.LanguageServer~.

3. Set executable to ~lsp-python-ms-executable~.

   #+BEGIN_SRC elisp
   ;; for executable of language server, if it's not symlinked on your PATH
   (setq lsp-python-ms-executable
         "~/python-language-server/output/bin/Release/osx-x64/publish/Microsoft.Python.LanguageServer")
   #+END_SRC

For development, you might find it useful to run =cask install=.

* FAQ

1. Unresolved import warnings

   Set workspace root of `lsp-mode` properly, and add the extra directories to =lsp-python-ms-extra-paths= or =PYTHONPATH=. 
   Refer to [[https://github.com/microsoft/python-language-server/blob/master/TROUBLESHOOTING.md#unresolved-import-warnings][Troubleshooting - Unresolved import warnings]] and [[https://github.com/emacs-lsp/lsp-python-ms/issues/96][#96]].

2. Autocompletion doesn't work

   The folder may have huge folders and files, and  the server takes a long time to index them. So please DO NOT put huge files in the project/workspace folder.

3. Set path of the Python executable for each project/workspace

   Set the variable =lsp-python-ms-python-executable= before the `lsp-mode` being loaded.

   First, add =hack-local-variables-hook= in `init.el` to achieve loading `lsp-mode` after the `.dir-locals.el` file of each project/workspace being loaded.

   #+BEGIN_SRC emacs-lisp
     (add-hook 'hack-local-variables-hook
	       (lambda ()
		 (when (derived-mode-p 'python-mode)
		   (require 'lsp-python-ms)
		   (lsp)))) ; or lsp-deferred
   #+END_SRC

   Second, create `.dir-locals.el` file in the root directory of project to specify the varibale =lsp-python-ms-python-executable= for the project/workspace.

   #+BEGIN_SRC emacs-lisp
     ((python-mode . ((lsp-python-ms-python-executable . "/.../bin/python"))))
   #+END_SRC

* Credit

All credit to [[https://cpbotha.net][cpbotha]] on [[https://vxlabs.com/2018/11/19/configuring-emacs-lsp-mode-and-microsofts-visual-studio-code-python-language-server/][vxlabs]]! This just tidies and packages his work there.