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https://github.com/bkomuves/toy-language-server
Example language server (LSP) implementation for a toy language
https://github.com/bkomuves/toy-language-server
haskell language-server language-server-protocol lsp
Last synced: 8 days ago
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Example language server (LSP) implementation for a toy language
- Host: GitHub
- URL: https://github.com/bkomuves/toy-language-server
- Owner: bkomuves
- License: bsd-3-clause
- Created: 2020-02-21T08:16:36.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2021-07-21T17:51:47.000Z (over 3 years ago)
- Last Synced: 2024-06-17T23:42:43.425Z (5 months ago)
- Topics: haskell, language-server, language-server-protocol, lsp
- Language: Haskell
- Homepage:
- Size: 313 KB
- Stars: 59
- Watchers: 2
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
Minimalistic language server (LSP) implementation
=================================================
Language server protocol example for a toy language implemented in Haskell,
using the [lsp](https://hackage.haskell.org/package/lsp) Haskell library
under the hood.
The "language" itself is very minimal to keep the implementation simple,
but the LSP support aims to be somewhat realistic.
IDE features
------------
* parsing, scope and type errors
* variable scope highlighting, shadowing info
* scope-aware renaming
* type information on hovering
* completion (colors + LaTeX style greek letters)
* jump to definition
* ad-hoc diagnostic (warnings for large numbers and rainbow color)
### Syntax highlighting
Syntax highlighting was not supported by the Language Server Protocol when
this was originally written... which is quite a serious instance of What. The. Fuck.
Apparently semantic highlighting finally comes with 3.16, but `lsp` does not
support that yet.
Instead, we have rudimentary syntax highlighting (in VS Code only) via *TextMate grammars*,
which are an abomination on earth if I've seen one...
The language
------------
Our toy language consists of top-level declarations.
Each declaration starts on a new line, and has the format:
```
indentifier : type = expression
```
There are three built-in types:
* `Bool`
* `Nat`
* `Color`
Expressions are built up from literal constants, variables, a built-in infix operator
(plus), and can use parentheses. Declarations are checked against the type.
For colors, we have a fixed list of pre-defined colors. Color names are
prefixed by a hash `#` character.
Example "program"
-----------------
```
the_truth : Bool = True
the_lie : Bool = the_truth
one : Nat = 1
fiftyfive : Nat = 50 + 4 + one
too_big : Nat = 12345
bad_number : Nat = (((666)))
ugly_col : Color = #black
nice_col : Color = #rainbow
```
Installation instructions (for VS Code)
--------------------------------------
1. Install `lsp` and `megaparsec`:
```
$ cabal install lsp
$ cabal install megaparsec
```
2. Build the server executable. This will hopefully build an executable `ToyLang-IDE.exe` and put it somewhere in the path:
```
$ cabal install
```
3. Install `npm` (if not already installed)
4. run the following (in the project directory!):
```
$ npm i vscode-languageclient
```
5. Install VS Code (if not already installed)
6. Open the project directory in VS Code
7. Press F5 to test the language server
8. Open a new text file and paste the example program above.
NB: You have to first save the file for the extension to be activated.
And choose the file extension `.toy`, otherwise nothing will happen!
9. Play around! For example, F2 does scope-aware renaming, and F12 is jump to definition.
You should see something like this:
To permanently install the extension, copy the whole project into
the extension folder (?):
* On Windows: `%USERPROFILE%\.vscode\extensions`
* On macOs / Linux: `~/.vscode/extensions`