Scala development with Vim in 2020

Chris Kipp

2020 ScalaUA

About Me

Grew up in the USA on a farm

Studied International Relations

Now based in the Netherlands

Software Engineer at Lunatech Labs

Enjoy working on tooling

& minimal tech

Switched careers to tech

Goals

~~Convince everyone here to switch to Vim and Metals~~
Show that Vim is not only a viable editor for Scala, but is well supported and feature rich
Show how fast it is to get up and running with Metals + Vim
Show a bit how Metals accounts for difference clients

Questions

Feel free to shoot them in the chat.

I'll either see them and address them as they come, or if I have time at the end.

Vim isn't going anywhere

2019

2018

2017

Stack Overflow Developer Surveys

2018 Scala Developer Survey

2019 Scala Developer Survey

Metals isn't going anywhere

Alexey Alekhin - @laughedelic
Johan Mudsam - @mudsam
Jorge Vicente Cantero - @jvican
Marek Żarnowski - @marek1840
Shane Delmore - @ShaneDelmore
Plus many more...

Ólafur Páll Geirsson

@olafurpg

Tomasz Godzik

@tgodzik

Gabriele Petronella

@gabro

LSP

ycm-core/YouCompleteMe (20.9K★ Python)
neoclide / coc.nvim (9.5K ★ - Node)
dense-analysis / ale (9.2K ★ - Vimscript)
autozimu / LanguageClient-neovim (2.8K ★ - Rust)
prabirshrestha / vim-lsp (1.5K ★ - Vimscript)
neovim / nvim-lsp (603 ★ - Lua)
natebosch / vim-lsc (418 ★ - Vimscript)

My recommendations depending on your situation

neoclide / coc.nvim (9.5K ★ - Node)
Coc is an intellisense engine for Vim/Neovim.
Same language server protocol support as VSCode
Allows you to re-use VSCode extensions (mostly)
Extremely responsive team

scalameta / coc-metals

scalameta / coc-metals

Plug 'neoclide/coc.nvim', {'branch': 'release'}

Paste recommended mappings into your .vimrc
1. ```
nmap <leader>rn <Plug>(coc-rename)
```

Either

```
:CocInstall coc-metals
```

Plug 'scalameta/coc-metals', {'do': 'yarn install --frozen-lockfile'}

With the assumption you have Node and Java Installed

coc-metals / importing builds

coc-metals / code actions

coc-metals / tree view protocol

coc-metals / worksheets

coc-metals / configuration

coc-metals / commands

coc-metals / doctor

coc-metals / run - debug

Via puremourning / vimspector

natebosch / vim-lsc (418 ★ - vimscript)
Covers the basics very well
Has some niceties like striking out deprecated methods
Easy setup
Pure vimscript

nvim / nvim-lsp (603 ★ - lua)
Built-in to nvim
Automated installation of servers
Extensible

Keep in mind that the support right now is pretty much experimental

Accounting for Clients

coursier bootstrap \
  --java-opt -Xss4m \
  --java-opt -Xms100m \
  --java-opt -Dmetals.client=vim-lsc \
  org.scalameta:metals_2.12:0.8.3 \
  -r bintray:scalacenter/releases \
  -r sonatype:snapshots \
  -o /usr/local/bin/metals-vim -f

https://scalameta.org/metals/docs/editors/new-editor.html#metals-server-properties

Server Properties

Accounting for Clients

interface ClientCapabilities {
  ...
  
  /**
    * User provided initialization options.
    * */
  initializationOptions?: any;
 }

https://microsoft.github.io/language-server-protocol/specifications/specification-current/#initialize

Initialization Options

Accounting for Clients

interface ClientCapabilities {
  ...
  
  /**
    * Experimental client capabilities.
    */
  experimental?: any;
 }

https://microsoft.github.io/language-server-protocol/specifications/specification-current/#initialize

Client Experimental Capabilities

The future

Continued (attempted) parity with VS Code + Metals
Built in LSP Client for Neovim
Onivim2 release
Updated Scala syntax highlighting for Vim

Final tips for coc-metals users

Make sure you have

```
"metals.statusBarEnabled": true
```
```
"codeLens.enable": true
```

Customize the recommended mappings
Give nvim a try if you're a vim user
Use the built-in commands
- metals.new-scala-file
- metals.revealInTreeView
- etc...

Thank you

@ckipp01

https://github.com/scalameta/coc-metals

chris-kipp.io/slides-vim-scala-2020.html

https://github.com/scalameta/metals

https://www.lunatech.com/