implement language server stub

esql-lsp/.eslintignore

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+node_modules/**
+client/node_modules/**
+client/out/**
+server/node_modules/**
+server/out/**

esql-lsp/.eslintrc.js

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+/**@type {import('eslint').Linter.Config} */
+// eslint-disable-next-line no-undef
+module.exports = {
+	root: true,
+	parser: '@typescript-eslint/parser',
+	plugins: [
+		'@typescript-eslint',
+	],
+	extends: [
+		'eslint:recommended',
+		'plugin:@typescript-eslint/recommended',
+	],
+	rules: {
+		'semi': [2, "always"],
+		'@typescript-eslint/no-unused-vars': 0,
+		'@typescript-eslint/no-explicit-any': 0,
+		'@typescript-eslint/explicit-module-boundary-types': 0,
+		'@typescript-eslint/no-non-null-assertion': 0,
+	}
+};

esql-lsp/.gitignore

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+out
+node_modules
+client/server
+.vscode-test

esql-lsp/.vscode/extensions.json

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+{
+	"recommendations": [
+		// https://github.com/smith/esql-tools syntax highlighting
+	]
+}

esql-lsp/.vscode/launch.json

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+// A launch configuration that compiles the extension and then opens it inside a new window
+{
+	"version": "0.2.0",
+	"configurations": [
+		{
+			"type": "extensionHost",
+			"request": "launch",
+			"name": "Launch Client",
+			"runtimeExecutable": "${execPath}",
+			"args": ["--extensionDevelopmentPath=${workspaceRoot}"],
+			"outFiles": ["${workspaceRoot}/client/out/**/*.js"],
+			"preLaunchTask": {
+				"type": "npm",
+				"script": "watch"
+			}
+		},
+		{
+			"name": "Language Server E2E Test",
+			"type": "extensionHost",
+			"request": "launch",
+			"runtimeExecutable": "${execPath}",
+			"args": [
+				"--extensionDevelopmentPath=${workspaceRoot}",
+				"--extensionTestsPath=${workspaceRoot}/client/out/test/index",
+				"${workspaceRoot}/client/testFixture"
+			],
+			"outFiles": ["${workspaceRoot}/client/out/test/**/*.js"]
+		}
+	]
+}

esql-lsp/.vscode/settings.json

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+{
+	"editor.insertSpaces": false,
+	"typescript.tsc.autoDetect": "off",
+	"typescript.preferences.quoteStyle": "single",
+	"editor.codeActionsOnSave": {
+		"source.fixAll.eslint": "explicit"
+	}
+}

esql-lsp/.vscode/tasks.json

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+{
+	"version": "2.0.0",
+	"tasks": [
+		{
+			"type": "npm",
+			"script": "compile",
+			"group": "build",
+			"presentation": {
+				"panel": "dedicated",
+				"reveal": "never"
+			},
+			"problemMatcher": [
+				"$tsc"
+			]
+		},
+		{
+			"type": "npm",
+			"script": "watch",
+			"isBackground": true,
+			"group": {
+				"kind": "build",
+				"isDefault": true
+			},
+			"presentation": {
+				"panel": "dedicated",
+				"reveal": "never"
+			},
+			"problemMatcher": [
+				"$tsc-watch"
+			]
+		}
+	]
+}

esql-lsp/.vscodeignore

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+.vscode/**
+**/*.ts
+**/*.map
+.gitignore
+**/tsconfig.json
+**/tsconfig.base.json
+contributing.md
+.travis.yml
+client/node_modules/**
+!client/node_modules/vscode-jsonrpc/**
+!client/node_modules/vscode-languageclient/**
+!client/node_modules/vscode-languageserver-protocol/**
+!client/node_modules/vscode-languageserver-types/**
+!client/node_modules/{minimatch,brace-expansion,concat-map,balanced-match}/**
+!client/node_modules/{semver,lru-cache,yallist}/**

esql-lsp/Makefile

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+
+.PHONY: deps
+deps:
+	sudo apt install openjdk-11-jre-headless
+	# download https://www.antlr.org/download.html latest

esql-lsp/README.md

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+# ES|QL LSP
+
+**WARNING**: experimental. Very exprimental.
+
+## Requirements
+
+Java 11 is required to run `antlr4ng-cli`, only needed in development to update TS code generated from ANTLR4 grammar files.
+
+## Functionality
+
+This Language Server works for `.esql` files. It *aims* hat having the following language features:
+- Completions (not fully working)
+- Diagnostics (not implemented)
+
+Developer can rely on the e2e test suite to verify behaviour.
+
+
+### What works
+
+Autocomplete for source tokens.
+
+### What does not work
+
+Everything else.
+
+## Structure
+
+```
+.
+├── client // Language Client
+│   ├── src
+│   │   ├── test // End to End tests for Language Client / Server
+│   │   └── extension.ts // Language Client entry point
+├── package.json // The extension manifest.
+└── server // Language Server
+    └── src
+        └── server.ts // Language Server entry point
+```
+
+## Running the Sample
+
+**Note**: You need JRE installed, version 11.
+
+- Run `npm install` in this folder. This installs all necessary npm modules in both the client and server folder
+- Open VS Code on this folder.
+- Press Ctrl+Shift+B to start compiling the client and server in [watch mode](https://code.visualstudio.com/docs/editor/tasks#:~:text=The%20first%20entry%20executes,the%20HelloWorld.js%20file.).
+- Switch to the Run and Debug View in the Sidebar (Ctrl+Shift+D).
+- Select `Launch Client` from the drop down (if it is not already).
+- Press ▷ to run the launch config (F5).
+- In the [Extension Development Host](https://code.visualstudio.com/api/get-started/your-first-extension#:~:text=Then%2C%20inside%20the%20editor%2C%20press%20F5.%20This%20will%20compile%20and%20run%20the%20extension%20in%20a%20new%20Extension%20Development%20Host%20window.) instance of VSCode, open a document in 'esql' language mode.
+  - Type `f` or press `ctrl+space` to see completions.