crystalline

This README is the one indexed from the repository at its latest ref, not from the tag for this version.

<div align="center">
	<img src="assets/icon.svg" width="128" height="128" />
	<h1>crystalline</h1>
  <h3>A Language Server for Crystal.</h3>
  <a href="https://github.com/elbywan/crystalline/actions?query=branch%3Amaster+workflow%3ABuild"><img alt="Build Status" src="https://github.com/elbywan/crystalline/workflows/Build/badge.svg?branch=master"></a>
  <a href="https://github.com/elbywan/crystalline/tags"><img alt="GitHub tag (latest SemVer)" src="https://img.shields.io/github/v/tag/elbywan/crystalline"></a>
  <a href="https://github.com/elbywan/crystalline/blob/master/LICENSE"><img alt="GitHub" src="https://img.shields.io/github/license/elbywan/crystalline"></a>
</div>

<hr/>

**`Crystalline` is an implementation of the
[Language Server Protocol](https://microsoft.github.io/language-server-protocol/)
written in and for the [Crystal Language](https://crystal-lang.org/). 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.**

<hr/>

<div align="center">
<img src="assets/small_demo.gif" height="300" width="360"/>
</div>

## Installation

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

### Compatibility

| Crystal   | Crystalline |
| --------- | ----------- |
| **1.20**  | **0.18**    |
| 1.16      | 0.17        |
| 1.15      | 0.16        |
| 1.14      | 0.15        |
| 1.13      | 0.14        |
| 1.12      | 0.13        |
| 1.11      | 0.12        |
| 1.10      | 0.11        |
| 1.9       | 0.10        |
| 1.8       | 0.9         |
| 1.7       | 0.8         |
| 1.6       | 0.7         |
| 1.4       | 0.6         |
| 1.3       | 0.5         |
| 1.2       | 0.4         |
| 1.1       | 0.4         |
| 1.0       | 0.3         |
| 0.36      | 0.2         |
| 0.35.1    | 0.1         |

### Pre-built binaries

#### Latest Release

##### Linux (x86_64)

```sh
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

```sh
yay -S crystalline
```

##### MacOS

Install using [homebrew](https://brew.sh):

```sh
brew install crystalline
```

#### Specific release

[See the releases page.](https://github.com/elbywan/crystalline/releases)

#### Specific commit

[Binaries are uploaded as artifacts during the CI
build.](https://github.com/elbywan/crystalline/actions)

### 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:

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

Then:

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

#### Global install

```sh
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._

<details><summary><strong>llvm-config path</strong></summary>
<p>

`llvm` is required in order to build `crystalline`, if you get the following
error message it means that the crystal compiler is unable to locate the
`llvm-config` binary:

```sh
--: : 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
```

This can be solved by adding the location of the `llvm-config` binary to the
`LLVM_CONFIG` environment variable. (or the containing directory to the `PATH`
env. variable)

For instance on a typical macOS setup, prefixing the command with the following
declaration would solve the issue:

```sh
# 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
```

> Replace `env` by `export` on Debian and derived (Ubuntu, Mint, ...)

</p>
</details>

<details><summary><strong>ld: library not found for -llibxml2.tbd</strong></summary>
<p>

LLVM **10.0.1** has some issues when reporting required system libraries on
macOS.

More info: [here](https://github.com/ziglang/zig/issues/6087)

```sh
# 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…
```

A hacky solution until llvm produces a solution would be to add a symbolic link
to the correct shared library file:

`ln -s /usr/lib/libxml2.2.dylib /usr/local/lib/liblibxml2.tbd.dylib`

Or just use a different LLVM major version until this issue is fixed upstream.

</p>
</details>

## Usage

`Crystalline` is meant to be used alongside an editor extension.

#### VSCode

- Add the
  [Crystal Language extension](https://marketplace.visualstudio.com/items?itemName=crystal-lang-tools.crystal-lang).

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

![vscode screen](assets/vscode_extension_screen.png)

- 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](https://github.com/vim-crystal/vim-crystal) plugin.
- Download [CoC](https://github.com/neoclide/coc.nvim) plugin.
- Make sure `crystalline` binary is in your PATH.

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

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

#### Emacs

- Download the `crystal-mode` [package](https://melpa.org/#/crystal-mode).
- Download the `lsp-mode` [package](https://melpa.org/#/lsp-mode).
- 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:
```elisp
(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.

```yml
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.

```yml
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.

```crystal
# 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:

```yml
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, `require`s will still be resolved relative to the project directory rather than the root directory.

### Compilation flags

To use specific compilation flags, you can add a `crystalline/flags` key in the `shard.yml` file:

```yml
crystalline:
  flags:
    - preview_mt
    - execution_context
```

## 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](https://github.com/samueleaton/sentry) is used to re-build crystalline
in debug mode on code change.

```sh
# 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.

```crystal
# 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:

```crystal
# 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](https://github.com/elbywan/crystalline/graphs/contributors)

## Credit

- [Scry](https://github.com/crystal-lang-tools/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](https://www.flaticon.com/authors/smashicons) from
  [www.flaticon.com](https://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`.

![guy roux](assets/guyroux.gif)