Dark

This is the main repo for Dark, a combined language, editor, and infrastructure to make it easy to build backends.

This repo is intended to help Dark users solve their needs by fixing bugs, expanding features, or otherwise contributing. Dark is source available, not open source.

Contributing

We are committed to make Dark easy to contribute to. Our contributor docs will help guide you through your first PR, find good projects to contribute to, and learn about the code base.

Getting started

We try to make it really easy to get started. If you have any problems, please ask in Slack and we'll work to fix any issues you have.

If you're using VSCode, we run our build scripts the VSCode devcontainer. See [docs/vscode-setup](the VSCode instructions) for a complete guide. Do not use the standard instructions, as lots of things will be subtly wrong.

Install dependencies

We develop Dark within a docker container, so there is not a lot of setup. However, we do need to setup the host system in a few ways to support file watching, DNS, and of course Docker. This section guides you through that, for each OS.

OSX

To build and run the server you must have the following installed (and running):

Homebrew for Mac
Docker for Mac
The latest version of bash: brew install bash

Linux

Everything should just work on Linux, so long as you have docker installed and you are using bash 4 or later.

Windows

On Windows, you can run Dark in WSL2 (Windows Subsystem for Linux):

You must be on at least Windows 10 Version 2004, and you must run WSL 2 (docker does not work in WSL 1)
Follow the WSL 2 installation instructions
Follow the Docker for WSL 2 installation instructions
This section of the guide is incomplete. We would welcome further notes to make this foolproof.

Building and running for the first time

Now that the pre-requisites are installed, we should be able to build the development container in Docker, which has the exact right versions of all the tools we use.

Run scripts/builder --compile --watch --test
Wait until the terminal says "Initial compile succeeded" - this means the build server is ready. The builder script will sit open, waiting for file changes in order to recompile
If you see "initial compile failed", it may be a memory issue. If you're using OSX, ensure you have Docker For Mac configured to provide 4GB or more of memory, then rerun the builder script. (Sometimes just rerunning will work, too).
Open your browser to http://darklang.localhost:8000/a/dark/, username "dark", password "what"
Edit code normally - on each save to your filesystem, the app will be rebuilt and the browser will reload as necessary

Read the contributor docs

If you've gotten this far, you're now ready to contribute your first PR.

Advanced setup

Testing

Unit tests run when you specify --test to scripts/builder. You can run them as a once off using:

scripts/run-client-tests
scripts/run-backend-tests
scripts/run-fsharp-tests
scripts/run-rust-tests containers/stroller
scripts/run-rust-tests containers/queue-scheduler

Integration tests:

scripts/run-in-docker ./integration-tests/run.sh

You can also run integration tests on your (host) machine, which gives you some debugging ability, and typically runs faster:

./integration-tests/run.sh

There are good debugging options for integration testing. See integration-tests/README.

Running unix commands in the container

scripts/run-in-docker bash

Accessing the local db

scripts/run-in-docker psql -d devdb

Config files

Config files are in config/. Simple rule: anything that runs inside the container must use a DARK_CONFIG value set in config/, and cannot use any other env var.

Debugging the client

You can enable the FluidDebugger by mousing over the Gear in the left-sidebar. There is also "Enable debugger" which enables a legacy debugger that nobody uses and doesn't work well.

If you're using Chrome, enable Custom Formatters to see ReScript values in Chrome Dev Tools instead of their JS representation. From within Chrome Dev Tools, click "⠇", "Settings", "Preferences", "Enable Custom Formatters".

Debugging dotnet

REPL (fsi)

You can get a REPL with all of the Dark libraries loaded by running:

scripts/dotnet-fsi

Segfaults and crashes

When dotnet crashes, you can debug it by running:

`lldb -- [your command]

In LLDB, you can use dotnet's SOS plugin to read the stack, values, etc. See https://docs.microsoft.com/en-us/dotnet/framework/tools/sos-dll-sos-debugging-extension for instructions. The plugin is automatically loaded in lldb in the dev container.

Production Services

The app is split into backend/ and client/. Part of the backend is used in the client (jsanalysis), and one directory is shared (libshared). These are compiled to create libraries and binaries.

These are put into containers, whose definitions are in containers/. We also have some containers which are defined entirely in their directory (typically, these have a self-contained codebase).

The containers are used in services/. A service is typically a number of yaml files defining a kubernetes deployment, made up of one or more containers, which use binaries from the backend.

Some services do not use Dark's containers (eg, when we deploy 3rdparty code, such as "let's encrypt"). Some just have a single container (eg queue-scheduler and postgres-honeytail).

zag/dark