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Title: About Language Server Protocol and Kakoune text editor
Author: Solène
Date: 24 November 2020
Tags: kakoune editor openbsd
Description:
In this article I will explain how to install a lsp plugin for kakoune
to add language specific features such as autocompletion, syntax error
reporting, easier navigation to definitions and more.
The principle is to use "Language Server Protocol" (LSP) to communicate
between the editor and a daemon specific to a programming language.
This can be also done with emacs, vim and neovim using the according
plugins.
Language Server Protocol on Wikipedia
For python, _pyls_ would be used while for C or C++ it would be
_clangd_.
The how-to will use OpenBSD as a base. The package names may certainly
vary for other systems.
## Pre-requisites
We need _kak-lsp_ which requires rust and cargo. We will need git too
to fetch the sources, and obviously kakoune.
```shell command
# pkg_add kakoune rust git
```
## Building
Official building steps documentation
I recommend using a dedicated build user when building programs from
sources, without a real audit you can't know what happens exactly in
the build process. Mistakes could be done and do nasty things with your
data.
```shell command
$ git clone https://github.com/kak-lsp/kak-lsp
$ cd kak-lsp
$ cargo install --locked --force --path .
```
## Configuration
There are a few steps. kak-lsp has its own configuration file but the
default one is good enough and kakoune must be configured to run the
kak-lsp program when needed.
Take care about the second command if you built from another user, you
have to fix the path.
```shell command
$ mkdir -p ~/.config/kak-lsp
$ cp kak-lsp.toml ~/.config/kak-lsp/
```
This configuration file tells what program must be used depending of
the programming language required.
```Configuration file sample
[language.python]
filetypes = ["python"]
roots = ["requirements.txt", "setup.py", ".git", ".hg"]
command = "pyls"
offset_encoding = "utf-8"
```
Taking the configuration block for python, we can see the command used
is _pyls_.
For kakoune configuration, we need a simple configuration in
~/.config/kak/kakrc
```Configuration file sample
eval %sh{/usr/local/bin/kak-lsp --kakoune -s $kak_session}
hook global WinSetOption filetype=(rust|python|go|javascript|typescript|c|cpp) …
lsp-enable-window
}
```
Note that I used the full path of kak-lsp binary in the configuration
file, this is due to a rust issue on OpenBSD.
Link to Rust issue on github
## Trying with python
To support python programs you need to install python-language-server
which is available in pip. There are no package for it on OpenBSD. If
you install the program with pip, take care to have the binary in your
$PATH (either by extending $PATH to ~/.local/bin/ or by copying the
binary in /usr/local/bin/ or whatever suits you).
The pip command would be the following (your pip binary name may
change):
```shell command
$ pip3.8 install --user 'python-language-server[all]'
```
Then, opening python source file should activate the analyzer
automatically. If you add a mistake, you should see `!` or `*` in the
most left column.
## Trying with C
To support C programs, clangd binary is required. On OpenBSD it is
provided by the clang-tools-extra package. If clangd is in your $PATH
then you should have working support.
## Using kak-lsp
Now that it is installed and working, you may want to read the
documentation.
kak-lsp usage
I didn't look deep for now, the autocompletion automatically but may be
slow in some situation.
Default keybindings for "gr" and "gd" are made respectively for "jump
to reference" and "jump to definition".
Typing "diag" in the command prompt runs "lsp-diagnostics" which will
open a new buffer explaining where errors are warnings are located in
your source file. This is very useful to fix errors before compiling or
running the program.
## Debugging
The official documentation explains well how you can check what is
wrong with the setup. It consists into starting kak-lsp in a terminal
and kakoune separately and check kak-lsp output. This helped me a lot.
Official troubleshooting guide
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