code-server/docs/CONTRIBUTING.md

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# Contributing

- [Pull Requests](#pull-requests)
- [Requirements](#requirements)
- [Development Workflow](#development-workflow)
  - [Updating VS Code](#updating-vs-code)
- [Build](#build)
- [Structure](#structure)
  - [Modifications to VS Code](#modifications-to-vs-code)
  - [Currently Known Issues](#currently-known-issues)

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- [Detailed CI and build process docs](../ci)

## Pull Requests

Please create a [GitHub Issue](https://github.com/cdr/code-server/issues) for each issue
you'd like to address unless the proposed fix is minor.

In your Pull Requests (PR), link to the issue that the PR solves.

Please ensure that the base of your PR is the **master** branch. (Note: The default
GitHub branch is the latest release branch, though you should point all of your changes to be merged into
master).

## Requirements

The prerequisites for contributing to code-server are almost the same as those for
[VS Code](https://github.com/Microsoft/vscode/wiki/How-to-Contribute#prerequisites).
There are several differences, however. You must:

- Use Node.js version 12.x (or greater)
- Have [yarn](https://classic.yarnpkg.com/en/) installed (which is used to install JS packages and run development scripts)
- Have [nfpm](https://github.com/goreleaser/nfpm) (which is used to build `.deb` and `.rpm` packages and [jq](https://stedolan.github.io/jq/) (used to build code-server releases) installed
- Have [shfmt](https://pkg.go.dev/mvdan.cc/sh/v3) installed to run `yarn fmt` (requires Go is installed on your system)

The [CI container](../ci/images/debian10/Dockerfile) is a useful reference for all
of the dependencies code-server uses.

## Development Workflow

```shell
yarn
yarn watch
# Visit http://localhost:8080 once the build is completed.
```

To develop inside an isolated Docker container:

```shell
./ci/dev/image/run.sh yarn
./ci/dev/image/run.sh yarn watch
```

`yarn watch` will live reload changes to the source.

### Updating VS Code

If you need to update VS Code, you can update the subtree with one line. Here's an example using the version 1.52:

```shell
# Add vscode as a new remote if you haven't already and fetch
git remote add -f vscode https://github.com/microsoft/vscode.git

git subtree pull --prefix lib/vscode vscode release/1.52 --squash --message "Update VS Code to 1.52"
```

## Build

You can build using:

```shell
./ci/dev/image/run.sh ./ci/steps/release.sh
```

Run your build with:

```shell
cd release
yarn --production
# Runs the built JavaScript with Node.
node .
```

Build the release packages (make sure that you run `./ci/steps/release.sh` first):

```shell
IMAGE=centos7 ./ci/dev/image/run.sh ./ci/steps/release-packages.sh
# The standalone release is in ./release-standalone
# .deb, .rpm and the standalone archive are in ./release-packages
```

The `release.sh` script is equal to running:

```shell
yarn
yarn build
yarn build:vscode
yarn release
```

And `release-packages.sh` is equal to:

```shell
yarn release:standalone
yarn test:standalone-release
yarn package
```

For a faster release build, you can run instead:

```shell
KEEP_MODULES=1 ./ci/steps/release.sh
node ./release
```

## Structure

The `code-server` script serves an HTTP API for login and starting a remote VS Code process.

The CLI code is in [src/node](../src/node) and the HTTP routes are implemented in
[src/node/routes](../src/node/routes).

Most of the meaty parts are in the VS Code portion of the codebase under [lib/vscode](../lib/vscode), which we described next.

### Modifications to VS Code

In v1 of code-server, we had a patch of VS Code that split the codebase into a front-end
and a server. The front-end consisted of all UI code, while the server ran the extensions
and exposed an API to the front-end for file access and all UI needs.

Over time, Microsoft added support to VS Code to run it on the web. They have made
the front-end open source, but not the server. As such, code-server v2 (and later) uses
the VS Code front-end and implements the server. We do this by using a git subtree to fork and modify VS Code. This code lives under [lib/vscode](../lib/vscode).

Some noteworthy changes in our version of VS Code:

- Adding our build file, which includes our code and VS Code's web code
- Allowing multiple extension directories (both user and built-in)
- Modifying the loader, websocket, webview, service worker, and asset requests to
  use the URL of the page as a base (and TLS, if necessary for the websocket)
- Sending client-side telemetry through the server
- Allowing modification of the display language
- Making it possible for us to load code on the client
- Making it possible to install extensions of any kind
- Fixing issue with getting disconnected when your machine sleeps or hibernates
- Adding connection type to web socket query parameters

As the web portion of VS Code matures, we'll be able to shrink and possibly
eliminate our modifications. In the meantime, upgrading the VS Code version requires
us to ensure that our changes are still applied and work as intended. In the future,
we'd like to run VS Code unit tests against our builds to ensure that features
work as expected.

**Note**: We have [extension docs](../ci/README.md) on the CI and build system.

If the functionality you're working on does NOT depend on code from VS Code, please
move it out and into code-server.

### Currently Known Issues

- Creating custom VS Code extensions and debugging them doesn't work
- Extension profiling and tips are currently disabled