Overview

This is an experimental implementation of LSP based project intended to provide support for a DRL text editor.

It is composed of 2 parts: the server containing the actual LSP implementation and the client which is a VSCode extension consuming the services provided by the server.

The server is a plain Java/Maven project. Executing a mvn clean package in its folder will generate a jar file that will be automatically linked and consumed by the client when executed as a VSCode extension.

Server Architecture

The server part is composed of three modules:

1. drools-parser - responsible for actual drl-syntax parsing, eventually invoking a JAVA-LSP engine to read the RHS content (that is plain Java code); it depends on org.drools:drools-drl-ast
2. drools-completion - used to provide completion suggestion using the C3 engine; it depends on com.vmware.antlr4-c3:antlr4-c3 and on drools-parser
3. drools-lsp-server - the "gateway" between the client and the parsing/completion logic; by itself it should not implement any business logic, but should be concerned only with communication; it depends directly on drools-completion

VSCode Usage

1. Download the latest release of vscode-extension-drl-editor-<version>.vsix from here
2. Install the extension in VSCode by selecting Extensions (Ctrl+Shift+X) and then ... (top-right corner) and Install from VSIX... to install the downloaded file
3. Open a .drl file and start editing

Developer notes

Precompiled-server - no debug

1. package server side code with mvn clean package
2. goto client directory
3. issue npm install
4. issue code . to start VSCode in that directory
5. inside VSCode, select Run and Debug (Ctrl+Shift+D) and then start Run Extension
6. a new Extension Development Host window will appear, with drl extension enabled
7. to "debug" server-side event, add server.getClient().showMessage(new MessageParams(MessageType.Info, {text})); in server-side code

Connected remote server - debug

1. package server side code with mvn clean package
2. start server with DroolsLspTCPLauncher from IDE on debug mode; this will start the LSP-server listening on port 9925
3. goto client directory
4. issue npm install
5. issue code . to start VSCode in that directory
6. inside VSCode, select Run and Debug (Ctrl+Shift+D) and then start Debug Extension
7. the extensions will establish a connection to the server running at port 9925
8. a new Extension Development Host window will appear, with drl extension enabled
9. to "debug" server-side event, add breakpoints in server-side code

Neovim Usage

Neovim has built-in LSP support, however client configuration is a manual process. It can be made a lot easier, though, if you leverage some of the many plugins available to do the hard parts for you, as you will see in the example below. Please note:

• Neovim will connect to the drools-lsp-server directly, bypassing the VSCode client extension.
• You are required to have a java runtime environment installed on your system, either with the JAVA_HOME environment variable set, or with the java command locatable in your PATH.
• The example below only shows the relevant portions of one's nvim init.lua file, assuming user familiarity with Neovim configuration (including working with plugins and keymappings, among other things).

Example Configuration

1. Use packer.nvim (plugin installer) to install nvim-lspconfig (standard Neovim LSP configurations), mason.nvim (an excellent LSP/DAP/Linter/Formatter package manager), and mason-lspconfig.nvim (the mason.nvim to nvim-lspconfig bridge):

  use 'wbthomason/packer.nvim'
  use {
    'neovim/nvim-lspconfig',
    requires = {
      'williamboman/mason.nvim',
      'williamboman/mason-lspconfig.nvim',
    },
  }

2. Get mason up-and-running:

require('mason').setup {}
require('mason-lspconfig').setup {}

3. Initialize the drools-lsp server (configuration options here):

require('lspconfig').drools_lsp.setup {
  -- configuration options can be put here
  -- when using mason, nothing is required!
}

4. Add automatic filetype detection of DRL files (necessary to trigger the language server startup):

vim.cmd[[ autocmd BufRead,BufNewFile *.drl set filetype=drools ]]

5. Startup nvim anew, have packer install the plugins, have mason install the language server, and start editing DRL!

:PackerSync
:MasonInstall drools-lsp
:edit your.drl