# JavaScript/TypeScript language server

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This is a language server for JavaScript and TypeScript that adheres to the [Language Server Protocol (LSP)](https://github.com/Microsoft/language-server-protocol/blob/master/protocol.md). It uses [TypeScript's](http://www.typescriptlang.org/) LanguageService to perform source code analysis.


## Try it out

 - On [sourcegraph.com](https://sourcegraph.com/github.com/sourcegraph/javascript-typescript-langserver/-/blob/src/typescript-service.ts)
 - In [Visual Studio Code](https://github.com/sourcegraph/vscode-javascript-typescript) (as an alternative to the built-in TypeScript integration)
 - In [Eclipse Che](https://eclipse.org/che/)
 - In [NeoVim](https://github.com/autozimu/LanguageClient-neovim)
 - In [Sublime Text](https://lsp.readthedocs.io/en/latest/#javascripttypescript)

## Features

 - Hovers
 - Goto definition
 - Goto type definition
 - Find all references
 - Document symbols
 - Workspace symbol search
 - Rename
 - Completion
 - Signature help
 - Diagnostics
 - Quick fixes

## Run it from source

```bash
# install dependencies
npm install

# compile
npm run build
# or compile on file changes
npm run watch

# run over STDIO
node lib/language-server-stdio
# or run over TCP
node lib/language-server

# run tests
npm test
```

## Options

```
  Usage: language-server [options]

  Options:

    -h, --help            output usage information
    -V, --version         output the version number
    -s, --strict          enabled strict mode
    -p, --port [port]     specifies LSP port to use (2089)
    -c, --cluster [num]   number of concurrent cluster workers (defaults to number of CPUs, 8)
    -t, --trace           print all requests and responses
    -l, --logfile [file]  log to this file
    -j, --enable-jaeger   enable OpenTracing through Jaeger
```

## Extensions

This language server implements some LSP extensions, prefixed with an `x`.

- **[Files extension](https://github.com/sourcegraph/language-server-protocol/blob/master/extension-files.md)**
  Allows the server to request file contents without accessing the file system
- **[SymbolDescriptor extension](https://github.com/sourcegraph/language-server-protocol/blob/master/extension-workspace-references.md)**
  Get a SymbolDescriptor for a symbol, search the workspace for symbols or references to it
- **[Streaming](https://github.com/sourcegraph/language-server-protocol/blob/streaming/protocol.md#partialResult)**
  Supports streaming partial results for all endpoints through JSON Patches
- **Packages extension**
  Methods to get information about dependencies
- **TCP / multiple client support**
  When running over TCP, the `exit` notification will not kill the process, but close the TCP socket

## Versioning

This project follows [semver](http://semver.org/) for command line arguments and standard LSP methods.
Any change to command line arguments, Node version or protocol breaking changes will result in a major version increase.

## Debugging Performance with OpenTracing

The language server is fully traced through [OpenTracing](http://opentracing.io/), which allows to debug what exact operations caused method calls to take long.
You can pass a span context through an optional `meta` field on the JSON RPC message object.

For local development, there is built-in support for the open source OpenTracing implementation [Jaeger](http://jaeger.readthedocs.io/en/latest/), which can be set up to run on localhost with just one command (you need [Docker](https://www.docker.com/) installed):

```
docker run -d -p5775:5775/udp -p6831:6831/udp -p6832:6832/udp \
  -p5778:5778 -p16686:16686 -p14268:14268 jaegertracing/all-in-one:latest
```

After that, run the language server with the `--enable-jaeger` command line flag and do some requests from your client.
Open http://localhost:16686 in your browser and you will see method calls broken down into spans.