crystalline

A Language Server for Crystal.

Crystalline is an implementation of the Language Server Protocol written in and for the Crystal Language. It aims to provide limited language features (like go-to, autocompletion, syntax and semantic checking) and ease development with any compatible code editor.

[!IMPORTANT]

Project Status

I am passively maintaining this project which means that I will not be regularly adding new features or fixing bugs. My time is very limited and I have other projects that I want to work on.

Crystalline begun as a fun experiment because at the time there was no working LSP for Crystal, and was written mainly to cater to my own needs - on my free time. I was happy to open-source it and share it with the community because I thought it could be useful to others.

But over time, some vocal people in the Crystal community have been openly trash-talking the project in the (un)official discord channel, telling users to avoid using it and spreading misinformation, which I am not cool with.

Crystalline has a bunch of issues, but if you know what you are doing, it can be a very useful tool. I know that because I am the primary user of it.

Due to the nature of the Crystal language and the way the compiler works, it is not possible to provide a full-fledged language server with all the features that one would expect. If you have a problem with that, then I suggest you use another language - or wait for someone else to write a better LSP (which I would be happy to see, but doubt will happen).

I am not paid to work on this project, I do it for fun.

And unfortunately, the fun has been sucked out of it.

Installation

Recommended method is to download and use pre-built binaries when possible. Building from source does take a long time.

Compatibility

Pre-built binaries

Latest Release

Linux (x86_64)

wget https://github.com/elbywan/crystalline/releases/latest/download/crystalline_x86_64-unknown-linux-musl.gz -O crystalline.gz &&\
gzip -d crystalline.gz &&\
chmod u+x crystalline

ArchLinux

yay -S crystalline

MacOS

Install using homebrew:

brew install crystalline

Specific release

See the releases page.

Specific commit

Binaries are uploaded as artifacts during the CI build.

Build from source

Warning: this can take a long time! (several minutes - up to 20 minutes, depending on your hardware)

Scoped install

In the .shard.yml file:

development_dependencies:
  crystalline:
    github: elbywan/crystalline
    branch: master

Then:

# Produces a binary at ./bin/crystalline
shards build crystalline --release --no-debug --progress -Dpreview_mt

Global install

git clone https://github.com/elbywan/crystalline
cd crystalline
shards install
mkdir bin
crystal build ./src/crystalline.cr  -o ./bin/crystalline --release --no-debug --progress -Dpreview_mt

Known Build Issues

Potential errors when building from source.

--: : command not found
Showing last frame. Use --error-trace for full trace.

In /usr/local/Cellar/crystal/0.35.1/src/llvm/lib_llvm.cr:13:17

 13 | VERSION = {{`#{LibLLVM::LLVM_CONFIG} --version`.chomp.stringify}}
                  ^
Error: error executing command: "" --version, got exit status 127

# Prepend the command with this:
env LLVM_CONFIG=/usr/local/opt/llvm/bin/llvm-config
# For Example:
env LLVM_CONFIG=/usr/local/opt/llvm/bin/llvm-config crystal build ./src/crystalline.cr  -o ./bin/crystalline --release --no-debug -Dpreview_mt

# Wrong: -llibxml2.tbd
$ llvm-config --system-libs
-lm -lz -lcurses -llibxml2.tbd
# `liblibxml2.tbd.dylib` is unlikely to be found during compilation,
# hence the "library not found" error…

Usage

Crystalline is meant to be used alongside an editor extension.

VSCode

• Add the Crystal Language extension.

• In the configuration, type the absolute location of the binary in the following field:

• Reload the window by pressing CMD/CTRL + SHIFT + P and select Developer: Reload Window (or as an alternative, restart VSCode).

Vim/Neovim

Using Conquer of Completion we can configure Crystalline as our LSP backend and get all the features of Crystalline we would get with VSCode.

• Download vim-crystal plugin.
• Download CoC plugin.
• Make sure crystalline binary is in your PATH.

Add the following snippet to your coc-settings.json file:

{
"languageserver": {
    "crystal": {
      "command": "crystalline",
      "args": [
        "--stdio"
      ],
      "filetypes": [
        "crystal"
      ],
      "rootPatterns": ["shard.yml"]
    }
  }
}

Emacs

• Download the crystal-mode package.
• Download the lsp-mode package.
• Make sure crystalline binary is in your PATH.

At the moment, lsp-mode only knows about scry as the Crystal language server. So, to get it working with crystalline we need to configure lsp-mode to look for crystalline.

You can use the following config snippet to achieve this:

(with-eval-after-load 'lsp-mode
  (add-to-list 'lsp-language-id-configuration
               '(crystal-mode . "crystal"))
  (lsp-register-client
  (make-lsp-client :new-connection (lsp-stdio-connection '("crystalline"))
                   :activation-fn (lsp-activate-on "crystal")
                   :priority '1
                   :server-id 'crystalline)))

This will give higher priority to crystalline, and Emacs should automatically connect to the backend whenever you're in crystal-mode.

Entry point

Important: Crystalline will try to determine which file is best suited as an entry point when providing language features.

The default behaviour is to check the shard.yml file for a target entry with the same name as the shard.

name: my_shard

targets:
  my_shard:
    main: src/entry.cr

With the configuration above, every file required by src/entry.cr will use src/entry.cr as the entry point.

If this shard.yml entry is not present, or if the file is not part of the main dependency tree then crystalline will use the file itself as the entry point.

To override this behaviour, you can add a configuration key in the shard.yml file.

crystalline:
  main: .crystalline_main.cr

This can be extremely important to understand when you are writing a code library that does not call any of its own methods - it will skip code analysis. In this case, and if you are writing specs, you should point to a file that require the specs (or anything calling the library) and then crystalline will use it as the entry point.

# Contents of a file at the root of the project.
# Will require the specs that call the library methods and enable the code analysis.
require "./spec/**"

Multiple projects

If you have multiple Crystal projects in a single folder (e.g. a monorepo), you can add a projects field in the root shard.yml file, containing an array of paths or globs to the underlying Crystal projects:

crystalline:
  projects:
    - projects/my_project_1
    - workspaces/**

Each of these projects must contain the shard.yml, ideally with the entry point as mentioned above. However, even if no entry point is present, requires will still be resolved relative to the project directory rather than the root directory.

Features

Disclaimer: Crystalline is not as extensive in terms of features as other Language Servers but still provides very convenient tools.

Code Diagnostics

Syntax and semantic checks on save.

Limited Autocompletion

List (depending on the target) method definitions, macros or module/class/struct names or symbols available in the current context.

Formatting

A whole document or a text selection.

Go to definition

By clicking on a symbol with the Cmd or Ctrl key pressed (editor/platform dependent).

Hover information

Hovering should display (when possible) either a variable type, a function definition signature or the expanded macro.

Document symbols

Fetch all the symbols in a given file, used in VSCode to populate the Outline view and the Breadcrumbs.

Limitations

• Memory usage is high due to the boehm GC behaviour and the crystal compiler itself. See: https://github.com/elbywan/crystalline/issues/23

• Due to Crystal having a wide type inference system (which is incredibly convenient and practical), compilation times can unfortunately be relatively long for big projects and depending on the hardware. This means that the LSP will be stuck waiting for the compiler to finish before being able to provide a response. Crystalline tries to mitigate that by caching compilation outcome when possible.

• Methods that are not called anywhere will not be analyzed, as this is how the Crystal compiler works.

• The parser is not permissive, nor incremental which means that the features will sometimes not work. It would involve a massive amount of work to change that.

Development

Dev build

Sentry is used to re-build crystalline in debug mode on code change.

# To build sentry (once):
shards build --release sentry
# Then, to launch it and watch the filesystem:
./bin/sentry -i

Logs

Logging is the most practical way to debug the LSP.

# Use the LSP logger to display logs in the editor.
LSP::Log.info { "log" }

Debug logs are deactivated by default, uncomment this line in src/crystalline/main.cr to enable them:

# Uncomment:
# ::Log.setup(:debug, LSP::Log.backend.not_nil!)

Contributing

1. Fork it (https://github.com/elbywan/crystalline/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Please always crystal tool format your code!

Contributors

Credit

• Scry, the original LSP for Crystal has been a great source of inspiration. I also re-used tiny bits of code from there.
• Icon made by Smashicons from www.flaticon.com.

Trivia

Why the name crystalline?

Aside of the obvious reasons (crystal-lang), cristaline is a famous bottled water brand in France that published silly TV commercials. It is pronounced the same as crystalline.