Guide to start contributing (coding focused)

[farie82]

Table of contents

• Intro
  • Quick DM tutorial
    • Object definitions (inheritance)
    • Procs (methods/functions)
    • Putting values easily in strings
    • Scoping
    • Deleting stuff
  • Coding Standards
  • Terminology
• Setup
• Your First PR
  • Finding The Relevant Code
    • Finding Existing Items
    • Finding Behaviour
    • Finding A Suitable Place To Add A New Item
    • Scoping
  • Solving The Actual Issue
    • Typo Or Grammar
    • Wrong Logic
    • Adding A New Item
  • Testing Your Code
  • Making The PR
• Tips And Tricks

Intro

Glad you're reading this and hopefully this guide will help you start contributing to this codebase!
First a word of wisdom. Start small with your first set of PRs even if you are already experienced with developing for other languages or codebases. Every codebase has its own quirks and standards which you will discover by doing and receiving feedback on your work.
This guide will help you set up your git and make your first PR. It will also include some tips on how to (in my opinion) best handle the codebase.
This guide will assume that you have at least (very) minor knowledge of how programming works. Knowing what a string is and how if statements work for example. The guide will also assume that you will use VS Code which the Setup section helps you set up.

Be sure to also take a look at the contributing page so you know what the coding standards are here.

I've also made a debugging tutorial which will help you find the cause of bugs and how to fix them.

Quick DM tutorial

For your first PR you won't need an in-depth knowledge of how to code in DM/SS13 but here are some of the basics that go for DM/SS13.
Feel free to skip these and come back to this once you feel like you are missing some info.

For more in-depth tutorials visit the wiki pages. SS13 code (beginner) and SS13 Code (experienced)
The DM reference guide is also great when you want to look up how a proc or such works. VS Code does have a build-in reference guide for you to use as well. Just CTRL-Click on any Byond proc or variable to see the reference on it.

Object definitions (inheritance)

An object is defined the following way:

/obj/item/multitool

Here we can see a multitool being defined. A multitool is an item which is an obj. This is how the class inheritance works for DM. A real-life example is that a dog is an animal and a cat is an animal. But a dog is not a cat. In DM it could look something like this:

/mob/animal/cat
	name = "Cat"

/mob/animal/dog
	name = "Dog"

Where mob is a being in DM. Thus something that "lives" and can do things.

Procs (methods/functions)

The way DM groups a set of instructions is as follows. It uses a proc or in other languages also called a method or function.

/obj/item/pen/multi/proc/select_colour(mob/user)
	var/newcolour = input(user, "Which colour would you like to use?", name, colour) as null|anything in colour_choices
	if(newcolour)
		colour = newcolour
		playsound(loc, 'sound/effects/pop.ogg', 50, 1)
		update_icon()

/obj/item/pen/multi/proc/select_colour here is the proc definition. Meaning this is the first instance of this proc. For this, you need to add proc/ in front of the method name (select_colour in this case). mob/user is here a parameter given to the proc. The name of the parameter is user and its type is mob.

As with other languages you can also override the behaviour of a proc.

/obj/item/pen/multi/attack_self(mob/living/user)
	select_colour(user)

Here the proc attack_self is overridden with new behaviour. It will call select_colour with as a parameter the given user.

When overriding a proc you can also call the parents implementation. This is especially handy when you want to extend the existing behaviour with new behaviour.

/obj/item/pen/multi/Initialize(mapload)
	. = ..()
	update_icon()

Here Initialize is overridden with mapload as a parameter. ..() means call the parent implementation of this proc with the parameters given to this version. So mapload will be passed through. . = ..() means assign the value that the parent's version returns as our default return value. . is the default return value in DM. So if you don't return an explicit value at the end of the proc then . will be returned.

/proc/test()
	. = "Yes"
	return "No"

This will return "No" since you explicitly state to return "No".

Small tip. You can also CTRL + Click on ..() to go to the parent's definition.

Putting values easily in strings

Other languages use something like string.format("{0} says {1}", mob_name, say_text). But DM has something nifty for that.
The same result can be achieved in DM using the following:

"[mob_name] says [say_text]"

[...] will run the code and return the outcome inside the []. In the case above it will just return the value of the variables but you can also use logic here.

var/val = 1
world.log << "val is [val]. val plus 10 is: [val + 10]"

Which will produce "val is 1. val plus 10 is: 11"

Scoping

If you come from another language then you might think. "Hey, where are the {}'s?!". Well, we do not use those (usually).
Instead scoping is done by whitespace. Tabs in our case. One tab means one scope deeper.

/mob
	name = "Thing"
/mob/proc/test()
	world.log << name // We can access name here since we are in the mob
	if(name == "Thing")
		var/value = 10
		world.log << "[value]" // We can also access value here since it is in the same scope or higher as us.
		world.log << "Will only happen if name is Thing"
	else
		world.log << "Will only happen if name is not Thing"
	world.log << "Will always happen even if name is not Thing"
	world.log << "[value]" // This will produce an error since value is not defined in our current scope or higher

In VS Code you can make your life easier by turning on the rendering of whitespace. Go to the settings and search for whitespace.

I have set it up so that I can only see the boundary whitespace. Meaning that I visually see spaces and tabs on the outmost left and right side of a line. Very handy in spotting indentation errors.

Deleting stuff

DM has a build-in proc called del. DO NOT USE THIS. del is very slow and gives us no control over properly destroying the object. Instead, most/all SS13 codebases have made their own version for this. qdel which will queue a delete for a given item. You should always call qdel when deleting an object. This will not only be better performance-wise but it will also ensure that other objects get notified about its deletion if needed.

Coding Standards

Before you start coding it is best to read our contributing page. It contains all of the coding standards and some tips and tricks on how to write good and safe code.

Terminology

Here is some terminology that will be used in the later text.

• PR, an abbreviation for pull request. This is the thing that will get your changes into the actual game. In short, it will say you request certain changes to be approved and merged into the master branch. Which is then used to run the actual game.
• VS Code, short for Visual Studio Code. The place where you do all your magic. It is both a text editor with a lot of helpful tools and a place where you can run and debug your code.
• Scoping, defining what code belongs to what. You don't want to make everything public to the whole codebase so you use scoping. See the explanation above for more info.
• Feature branch, the branch where your new feature or fix is located on. Git works with branches. Each branch containing a different version of the codebase. When making a PR git will look at the differences between your branch and the master branch.

Setup

I was going to make a step by step guide on here but our guide to contributing wiki page has a very extensive and comprehensible guide on how you set up your Git, GitHub and Visual Studio Code. I recommend following the guide over there and returning here once that is done.
I would 100% recommend using VS Code even though you could use another editor to make code changes. VS Code has a lot of great extensions which will make your life a whole lot easier. Things like debugging and just a great global search functionality.

Your First PR

Once you've completed the setup you can continue with making an actual PR.

I'd suggest keeping it small since setting up all of the git stuff was already a task of its own.
My suggestion would be to look at issues with the Good First Issue label. These usually are considered to be easy to solve.
Usually, they will also contain some comments containing hints on how to solve them. When picking one be sure that you do not pick an issue that already has an open PR attached to it like in the picture below.

You can make a PR that solves that issue. But it would be a waste of time since somebody else already solved it before you but their PR is still awaiting approval.

If there are no suitable good first issues then you can look through the issue list yourself to find some. Good ones include typos or small logic errors. If you know of any issues that are not yet listed in the issues list then those are also fine candidates.
Alternatively, you can implement a small new feature or change. Good examples include:

• More or changed flavour text to an item/ability etc.
• Adding (existing) sound effects to abilities/actions.
• Adding administrative logging where it is missing. For example, a martial arts combo not being logged.
• A new set of clothing or a simple item.

There of course are many more options that are not included in this list.

Finding The Relevant Code

The first thing you will need to do is to find the relevant code once you figured out what you want to add/change.
This is no exact science and requires some creative thinking but I will list a few methods I use myself when finding code.

For all of these, you will need to have VS code open and use the search functionality. I tend to only look for things in dm files. Which are the code files.

Finding Existing Items

If you're looking for an existing item then it might be easiest to look for the name of the item. Let's take a multitool as an example here.

When looking for the term multitool you will tend to find a lot of results. 305 results on my current version of the game in fact.

Alternatively, you can search for "multitool" (the string with the value multitool) and find a lot fewer results. For demonstration purposes, I will exclude the "" here. This will give you the following match:

This might seem like a lot (and it is) but you don't have to go through them all to find the item itself. Using some deduction we can find the result we need. Or find it via another result we found.
Here we can see that there are some matches with obj/item/multitool for example:

We know that we are looking for a multitool and that a multitool is an item so it looks like this is what we want to find.
When hovering over the multitool part of obj/item/multitool and holding the CTRL key you will see the definition of the object.

Perfect! This is the one we need. How how do we get to that definition? Simple you click on multitool when holding CTRL.
This will send you to the definition of the object.

Most of the times the file containing the definition will also include the looked for proc or value you want to change.

Finding Behaviour

This is a very wide concept and thus hard to exactly find.
For this, we will use the above method and use keywords explaining the behaviour you want to search. For example a mob gibbing.
Simply looking for gib here will find us too many results. About 1073 in my case.
Instead, we will try to look for a proc named gib. /gib( will be used as our search criteria here.

Et voila, just 15 results.

Say we want to delete the pet collar of animals such as Ian when he is gibbed. Here we need to find something stating that the gib belongs to an animal.

/mob/living/simple_animal/gib() is what we are looking for here. Ian is an animal. simple_animal in code.

This will find us the following code (on my current branch)

/mob/living/simple_animal/gib()
	if(icon_gib)
		flick(icon_gib, src)
	if(butcher_results)
		var/atom/Tsec = drop_location()
		for(var/path in butcher_results)
			for(var/i in 1 to butcher_results[path])
				new path(Tsec)
	if(pcollar)
		pcollar.forceMove(drop_location())
		pcollar = null
	..()

The behaviour we're looking for here has to do with the pcollar code there. It will currently move the attached pet collar (if any) to the drop location of the animal when they are gibbed.

Finding A Suitable Place To Add A New Item

When adding a new item you want to ensure that it is placed in a logical file or that you make a new file in a logical directory.
I find that it is best to find other similar items and see how they are defined. For example a special jumpsuit without armour values.
Here we first go look for the existing non-job-related jumpsuits such as the "mailman's jumpsuit". Say we don't know the exact name of that jumpsuit but we do know that it is for a mailman.
Our best bet will be to look for the term mailman and see what pops up. This is a rather uncommon term so it should give only a few results.

Perfect. Even the item definition has the name mailman in it.

We already see from the search results that the item is defined in the miscellaneous.dm file. Navigating to it will show us the directory it is in.

As you can see most clothing items are defined in this clothing directory. Depending on your to add the item you can pick one of those files and see if it would fit in there. Feel free to ask for advice from others if you are unsure.

Solving The Actual Issue

Now comes the Fun part. How to achieve what you want to achieve?
The answer is. "That depends" Fun, isn't it?
Every problem has its own way of solving it. I will list some of the more common solutions to a problem down here. This list will of course not be complete.

A great hotkey for building your code quick is CTRL SHIFT B. Then press enter to select to build via Byond. This will start building your code in the console at the bottom of your screen (by default). It will also show any errors in the build process.

Here I have "accidentally" placed some text where it should not belong. Going to the "Problems" tab and clicking on the error will bring you to where it goes wrong.

This error does not tell much on its own (Byond is not great at telling you what goes wrong sometimes) but going to the location shows the problem quite easily.

More cases might be added later.

Typo Or Grammar

The easiest of them all if you can properly speak English.
Say the multitool description text is as follows "Used for pusling wires to test which to cut. Not recommended by doctors."
Then you can easily fix the typo by just changing the value of the string to the correct spelling.

Wrong Logic

This one really depends on the context. But let us take the following example. You cannot link machinery using a multitool. Something it should do.

/obj/item/multitool/proc/set_multitool_buffer(mob/user, obj/machinery/M)
	if(ismachinery(M))
		to_chat(user, "<span class='warning'>That's not a machine!</span>")
		return

Here a simple mistake is made. A ! is forgotten. ! will negate the outcome of any given value. In this case, a check to see if M is indeed a piece of machinery. This seems dumb to forget or do wrong but it can happen when a large PR gets made and is changed often. Testing every case is difficult and cases can slip under the radar.

Adding A New Item

You can start defining the new item once you found the proper file the item should belong to.
Depending on the item you will have to write different code (duh). We will take the new jumpsuit as an example again and will put it in the miscellaneous file.

When defining a new jumpsuit you can easily copy an existing one and change the definition values. We will take the mailman outfit as a template.

/obj/item/clothing/under/rank/mailman
	name = "mailman's jumpsuit"
	desc = "<i>'Special delivery!'</i>"
	icon_state = "mailman"
	item_state = "b_suit"
	item_color = "mailman"

As seen here a jumpsuit has multiple values you can define. The name is pretty straight forward. desc is the description of the item. icon_state is the name the sprite has in the DMI file. item_state is the name of the sprite of the suit while held in your hands has in the DMI file. item_color is the name of the sprite in the icons/mob/uniform.dmi file. This value will indicate what sprite will be used when a person wears this jumpsuit. (I know item_color is a weird name for this)

We of course also have to change the path of the newly created object. We'll name it /obj/item/clothing/under/rank/tutorial.
This alone will make it so that you can spawn the item using admin powers. It will not automagically appear in vendors or such.

Testing Your Code

Once you are done coding you can start testing your code, assuming your code compiles of course.

To do this simply press F5 on your keyboard. This will by default build your code and start the game with a debugger attached. This allows you to debug the code in more detail.

Later I will include a more detailed testing plan in this guide.

Making The PR

Once you are done with your changes you can make a new PR.

If you did not create a new branch in the Setup phase. Then you are still fine. Before committing make a new branch from your master branch. If you have already done this then skip two steps forward.

Select "Create new branch" and then give your new branch a name in the top text bar in VS code. Press enter once you are done and you will have created a new branch. Your saved changes will be carried over to the new branch.

You are ready to commit the changes once you are on your feature branch and when the code is done and tested.
Simply write a (short) useful commit message explaining what you've done.
For example when implementing the pet collar gibbing example

Here you can also see the changes you have made. Clicking on a file will show you the difference between how it was before and how it is now.
When you are happy with the existing changes you can press the commit button. The checkmark. By default it will commit all the changes there are unless you staged changes. Then it will only commit the staged changes. Handy when you want to commit some code while you have some experimental code still there.

Once it is committed you will have to also publish the branch.

When pressing push it will ask you if you want to publish the branch since there is no known remote version of this yet (not on Github). Say yes to that and select "origin" from the list of available remotes. Now your code is safely pushed to Github.

Now go to the Github page of this codebase and you will see the following:

Click on the green button and Github will auto-create a PR template for you for the branch you just pushed.
Be sure to fill in the template shown to you. It is quite straight forward but it is important to note down the thing you changed in enough detail.
If you fixed an issue then you can write the following fixes #12345 where 12345 is the number of the issue. Put this line of text in the What Does This PR Do part of the PR.

You can submit it once you are happy with how the PR looks. After this, your PR will be made public and visible to others to review. In due time a maintainer will look at your PR and will merge it if it is deemed an addition to the codebase.

Tips And Tricks

Here I will list some of my tips and tricks that can be useful for you when developing our codebase.

• Sounds like a simple and logical one. But always feel free to ask others for help/advice. This project is an open-source project run by a lot of passionate people who want to improve the codebase together. Asking for help/advice will not only help you get your code running but will also show you are interested and will help you improve your skills.
• Learn the VS Code shortcuts. This really saves you a lot of time. CTRL + SHIFT + B will build your project. F5 will run it in debug mode. CTRL + SHIFT + F will global search. CTRL + P will find definitions of things (super handy)
• Use find references when right-clicking on a variable or proc. This will list all the uses of this var/proc so you can see what it is actually used for or where you need to change things as well etc.
• You can remove the build command from F5. This saves you some time when you develop. Be sure to manually build your code though! This can be done by removing the preLaunchTask line in the debug config:
  

TODOs

This guide is far from final and will later include the following topics:

• More examples for searching and such
• Code styling. Coding standards etc
• More...

Be sure to comment your suggestions for this guide as that will help me improve it!