urbit/CONTRIBUTING.md

Contributing to urbit

Thank you for your interest in contributing to urbit.

Fake ~zods

You may have an identity on the live network, but doing all your development on the live network would be cumbersome and unnecessary. Standard practice in urbit development is to work on a fake ~zod. A fake ~zod will get its initial files from a directory you specify rather than trying to sync them over the network, which is invaluable for working in Hoon. Also, a fake ~zod or any fake urbit instances you start do not talk to the live network, but to a fake network that exists only on your computer.

First, you'll want to check out the Arvo repository. Arvo is kept in its own repository, and changes more rapidly than the main C project does.

git clone https://github.com/urbit/arvo

The arvo repository can live safely inside the main urbit repository if you want, since it's listed in .gitignore. However, vere will use the path you specify on the command line with the -A option.

To start a fake ~zod, the command is:

$ urbit -c -F -I zod -A [arvo checkout] [pier directory]

To resume one that was already created, just as on the live network, remove -c and -A [arvo checkout] (but leave the rest of the options there). -F uses the fake network, and -I starts an "imperial" instance - that is, an 8-bit galaxy.

Kernel development

Working on either C or non-kernel Hoon should not bring any surprises, but the Hoon kernel (anything under arvo/arvo/) is bootstrapped from urbit.pill, and must be recompiled if any changes are made. This should happen automatically when you make changes, but if it doesn't, the command to manually recompile the kernel and install the new kernel is |reset in dojo. This rebuilds from the arvo directory in the home desk in %clay. Currently, |reset does not reload apps like dojo itself, which will still reference the old kernel. To force them to reload, make a trivial edit to their main source file (under the app directory) in %clay.

If you do any kernel development, be sure to read the section below about pills.

Git practice

Since we use the GitHub issue tracker, it is helpful (though not required) to contribute via a GitHub pull request. If you already know what you are doing, skip down to the Style section.

Start by cloning the repository on your work machine:

git clone https://github.com/urbit/urbit

And, additionally, fork the repository on GitHub by clicking the "Fork" button. Add your fork as a remote:

git remote add [username] https://github.com/[username]/urbit

and set it as the default remote to push to:

git config --local remote.pushDefault [username]

This is good practice for any project that uses git. You will pull upstream branches from urbit/urbit and push to your personal urbit fork by default.

Next, start a new branch to do your work on. For urbit, please use the latest tagged release as your starting point. For other repositories, anywhere pointed to by master is alright to start from.

git checkout -b [branch name] [starting point]

Now you are free to do your work on this branch. When finished, you may want to clean up your commits:

git rebase -i [starting point]

Then you can push to your public fork with git push and make a pull request via the GitHub UI.

After your changes are merged upstream, you can delete your branch (via github UI or git push :[branch] remotely, and with git branch -d locally).

Style

The urbit project uses two-space indentation and avoids tab characters. In C code, it should not be too difficult to mimic the style of the code around you, which is just fairly standard K&R with braces on every compound statement. One thing to watch out for is top-level sections in source files that are denoted by comments and are actually indented one level.

Hoon will be a less familiar language to many contributors. Some of our less obvious stylistic rules are:

• Keep your source files 80 characters or less wide. Many urbit developers use 80 character terminals/tmux panes/&c.
• Tab characters are actually a syntax error, so be extra sure your editor is not inserting any. Trailing whitespace is usually not a syntax error, but avoiding it is encouraged.
• The kernel convention is that line comments start at column 57 with the :: followed by 2 spaces. This leaves 20 characters for the comment. Outside the kernel, things are less strict.
• Tall arms within a core are conventionally separated by empty comments (just ::) at the same indentation level as the initial ++ or +-. The last arm in a core is not followed by an empty comment, because it is visually closed by the -- that closes the core. The empty comment is also sometimes omitted in data structure definitions.

The kernel and pills

urbit bootstraps itself using a binary blob called urbit.pill. You probably remember it being fetched from bootstrap.urbit.org before your first boot. This is just the compiled version of the kernel, which you can find in the arvo/arvo/ directory - hoon.hoon, zuse.hoon, and so on.

The procedure for creating urbit.pill is often called "soliding". It is somewhat similar to |reset, but instead of replacing your running kernel, it writes the compiled kernel to a file. The command to solid is, on a fakezod:

.urbit/pill +solid

When the compilation finishes, your urbit.pill will be found in the [pier]/.urb/put/ directory.

Ordinarily, http://bootstrap.urbit.org/latest.pill will be updated to match whatever's on master in the arvo repository with every merge to master. Older pills will be stored with the git SHA1 of the relevant commit as [sha1].pill.

If you're doing heavy kernel hacking and want to submit intermediate pills for your branch, please include them with your pull request, and they'll be uploaded to bootstrap.urbit.org when your branch is merged.

Debug urbit with gdb

Follow the build instructions in README.md but run make with argument DEBUG=yes:

(If you've already built urbit first run make clean.)

make DEBUG=yes

Run gdb, while loading bin/urbit and its symbol table:

gdb bin/urbit

Set a breakpoint on main() (optional):

break main

Run your urbit comet mycomet:

run mycomet

Continue from the breakpoint on main():

continue

What to work on

If you are not thinking of contributing with a specific goal in mind, the GitHub issue tracker is the first place you should look for ideas. Issues are tagged with a priority and a difficulty. A good place to start is on either a low-difficulty issue or a low-priority issue. Higher priority issues are likely to be assigned to someone - if this is the case, then contacting that person to coordinate before starting to work is probably a good idea.

There is also a "help wanted" tag for things that we are especially eager to have outside contributions on. Check here first!

Staying in touch

The urbit developers communicate on urbit itself. Joining the urbit-meta channel on talk is highly recommended, as is reading the forums at http://urbit.org/fora. Subscribing to urbit-dev on Google Groups is also recommended, since this is where continuity breach notifications are sent.

Pull requests in non-GitHub forms can go to Raymond Pasco (ray@the.ug). Questions or other communications about contributing to Urbit can go to Raymond Pasco or Philip Monk (philip.monk@tlon.io).