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[ci-skip] update contributing guidelines with Paper's improvements (#663)

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CONTRIBUTING.md
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Contributing to Purpur
==========================
Purpur has a very lenient policy towards PRs, but would prefer that you try and adhere to the following guidelines.
Purpur is happy you're willing to contribute to our projects. We are usually
very lenient with all submitted PRs, but there are still some guidelines you
can follow to make the approval process go more smoothly.
## Use a Personal Fork and not Organization
Purpur will routinely modify your PR, whether it's a quick rebase or to take care
of any minor nitpicks we might have. Often, it's better for us to solve these
problems for you than make you go back and forth trying to fix it yourself.
Unfortunately, if you use an organization for your PR, it prevents Purpur from
modifying it. This requires us to manually merge your PR, resulting in us
closing the PR instead of marking it as merged.
We much prefer to have PRs show as merged, so please do not use repositories
on organizations for PRs.
See <https://github.com/isaacs/github/issues/1681> for more information on the
issue.
## Requirements
To get started with PRing changes, you'll need the following software, most of
which can be obtained in (most) package managers such as `apt` (Debian / Ubuntu;
you will most likely use this for WSL), `homebrew` (macOS / Linux), and more:
- `git` (package `git` everywhere);
- A Java 16 or later JDK (packages vary, use Google/DuckDuckGo/etc.).
- [Adoptium](https://adoptium.net/) has builds for most operating systems.
- Purpur requires JDK 16 to build, however makes use of Gradle's
[Toolchains](https://docs.gradle.org/current/userguide/toolchains.html)
feature to allow building with only JRE 8 or later installed. (Gradle will
automatically provision JDK 16 for compilation if it cannot find an existing
install).
If you're on Windows, check
[the section on WSL](#patching-and-building-is-really-slow-what-can-i-do).
If you're compiling with Docker, you can use Adoptium's
[`eclipse-temurin`](https://hub.docker.com/_/eclipse-temurin/) images like so:
```console
# docker run -it -v "$(pwd)":/data --rm eclipse-temurin:16.0.2_7-jdk bash
Pulling image...
root@abcdefg1234:/# javac -version
javac 16.0.2
```
## Understanding Patches
Patches to Purpur are very simple, but center around the directories 'Purpur-API' and 'Purpur-Server'
Assuming you already have forked the repository:
Purpur is mostly patches and extensions to Paper/Spigot. These patches/extensions are
split into different directories which target certain parts of the code. These
directories are:
1. Pull the latest changes from the main repository
2. Update the Paper submodule if necessary: `git submodule update --init --recursive` and `./gradlew setupUpstream`
3. Type `./gradlew applyPatches` to apply the latest Purpur patches
4. cd into `Purpur-Server` for server changes, and `Purpur-API` for API changes
- `Purpur-API` - Modifications to `Paper-API`;
- `Purpur-Server` - Modifications to `Purpur`.
These directories aren't Git repositories in the traditional sense:
Because the entire structure is based on patches and git, a basic understanding
of how to use git is required. A basic tutorial can be found here:
<https://git-scm.com/docs/gittutorial>.
- Every single commit in Purpur-Server/API is a patch.
- 'origin/master' points to a directory similar to Purpur-Server/API but for Paper
- Typing `git status` should show that we are 10 or 11 commits ahead of master, meaning we have 10 or 11 patches that Paper doesn't
- If it says something like `212 commits ahead, 207 commits behind`, then type `git fetch` to update Purpur
Assuming you have already forked the repository:
1. Clone your fork to your local machine;
2. Type `./gradlew applyPatches` in a terminal to apply the changes from upstream.
On Windows, leave out the `./` at the beginning for all `gradlew` commands;
3. cd into `Purpur-Server` for server changes, and `Purpur-API` for API changes.
<!--You can also run `./paper server` or `./paper api` for these same directories
respectively.
1. You can also run `./paper setup`, which allows you to type `paper <command>`
from anywhere in the Paper structure in most cases.-->
`Purpur-Server` and `Purpur-API` aren't git repositories in the traditional sense:
- `base` points to the unmodified source before Purpur patches have been applied.
- Each commit after `base` is a patch.
## Adding Patches
Adding patches to Purpur is very simple:
1. Modify `Purpur-Server` and/or `Purpur-API` with the appropriate changes
2. `cd` into the server/api directory you want to add a patch to
3. Type `git add .` to add your changes
4. Run `git commit` with the desired patch message
5. `cd ../` to get back to the project root
6. Run `./gradlew rebuildPatches` in the main directory to convert your commit into a new patch
7. PR your patches back to this repository
1. Modify `Purpur-Server` and/or `Purpur-API` with the appropriate changes;
1. Type `git add .` inside these directories to add your changes;
1. Run `git commit` with the desired patch message;
1. Run `./gradlew rebuildPatches` in the main directory to convert your commit into a new
patch;
1. PR the generated patch file(s) back to this repository.
Your commit will be converted into a patch that you can then PR into Purpur.
## Help! I can't find the file I'm looking for!
By default, Purpur (and upstream) only import files that we make changes to.
If you would like to make changes to a file that isn't present in Purpur-Server's source directory, you
just need to add it to our import script to be ran during the patch process.
1. Save (rebuild) any patches you are in the middle of working on!
2. Identify the names of the files you want to import.
- A complete list of all possible file names can be found at ```./Paper/work/Minecraft/$MCVER/net/minecraft/server```
3. Edit the `mcdevimports.conf` file and add the name of your file to the `nms-imports` list.
4. Re-patch the server to make the imports take effect `./gradlew applyPatches`
5. Edit away!
This change is temporary! DO NOT COMMIT CHANGES TO THE `mcdevimports.conf` FILE!
Once you have made your changes to the new file, and rebuilt patches, you may undo your changes to `mcdevimports.conf`
Any file modified in a patch file gets automatically imported, so you only need this temporarily
to import it to create the first patch.
To undo your changes to the file, delete the `mcdevimports.conf` file and re-apply patches, or just remove the import lines you added previously.
> ❗ Please note that if you have some specific implementation detail you'd like
> to document, you should do so in the patch message *or* in comments.
## Modifying Patches
Modifying previous patches is a bit more complex:
### Method 1
This method works by temporarily resetting HEAD to the desired commit to edit using rebase.
However, while in the middle of an edit, unless you also reset your API to a related commit, you will not be able to compile.
This method works by temporarily resetting your `HEAD` to the desired commit to
edit it using `git rebase`.
1. If you have changes you are working on type `git stash` to store them for later.
- Later you can type `git stash pop` to get them back.
2. Type `git rebase -i origin/master`
- It should show something like [this](https://gist.github.com/zachbr/21e92993cb99f62ffd7905d7b02f3159).
3. Replace `pick` with `edit` for the commit/patch you want to modify, and "save" the changes.
- Only do this for one commit at a time.
4. Make the changes you want to make to the patch.
5. Type `git add .` to add your changes.
6. Type `git commit --amend` to commit.
- **MAKE SURE TO ADD `--amend`** or else a new patch will be created.
- You can also modify the commit message here.
7. Type `git rebase --continue` to finish rebasing.
8. Type `./gradlew rebuildPatches` in the main directory.
- This will modify the appropriate patches based on your commits.
9. PR your modifications back to this project.
> ❗ While in the middle of an edit, you will not be able to compile unless you
> *also* reset the opposing module(s) to a related commit. In the API's case,
> you must reset the Server, and reset the API if you're editing the Server.
> Note also that either module _may_ not compile when doing so. This is not
> ideal nor intentional, but it happens. Feel free to fix this in a PR to us!
### Method 2 (sometimes easier)
If you are simply editing a more recent commit or your change is small, simply making the change at HEAD and then moving the commit after you have tested it may be easier.
1. If you have changes you are working on, type `git stash` to store them for
later;
- You can type `git stash pop` to get them back at any point.
1. Type `git rebase -i base`;
- It should show something like
[this](https://gist.github.com/zachbr/21e92993cb99f62ffd7905d7b02f3159) in
the text editor you get.
- If your editor does not have a "menu" at the bottom, you're using `vim`.
If you don't know how to use `vim` and don't want to
learn, enter `:q!` and press enter. Before redoing this step, do
`export EDITOR=nano` for an easier editor to use.
1. Replace `pick` with `edit` for the commit/patch you want to modify, and
"save" the changes;
- Only do this for **one** commit at a time.
1. Make the changes you want to make to the patch;
1. Type `git add .` to add your changes;
1. Type `git commit --amend` to commit;
- **Make sure to add `--amend`** or else a new patch will be created.
- You can also modify the commit message and author here.
1. Type `git rebase --continue` to finish rebasing;
1. Type `./gradlew rebuildPatches` in the root directory;
- This will modify the appropriate patches based on your commits.
1. PR your modified patch file(s) back to this repository.
This method has the benefit of being able to compile to test your change without messing with your API HEAD.
### Method 2 - Fixup commits
1. Make your change while at HEAD
2. Make a temporary commit. You don't need to make a message for this.
3. Type `git rebase -i origin/master`, move (cut) your temporary commit and move it under the line of the patch you wish to modify.
4. Change the `pick` with `f` (fixup) or `s` (squash) if you need to edit the commit message
5. Type `./gradlew rebuildPatches` in the main directory
- This will modify the appropriate patches based on your commits
6. PR your modifications back to this project.
If you are simply editing a more recent commit or your change is small, simply
making the change at HEAD and then moving the commit after you have tested it
may be easier.
This method has the benefit of being able to compile to test your change without
messing with your HEADs.
#### Manual method
1. Make your change while at HEAD;
1. Make a temporary commit. You don't need to make a message for this;
1. Type `git rebase -i base`, move (cut) your temporary commit and
move it under the line of the patch you wish to modify;
1. Change the `pick` to the appropriate action:
1. `f`/`fixup`: Merge your changes into the patch without touching the
message.
1. `s`/`squash`: Merge your changes into the patch and use your commit message
and subject.
1. Type `./gradlew rebuildPatches` in the root directory;
- This will modify the appropriate patches based on your commits.
1. PR your modified patch file(s) back to this repository.
#### Automatic method
1. Make your change while at HEAD;
1. Make a fixup commit. `git commit -a --fixup <hashOfPatchToFix>`;
- You can also use `--squash` instead of `--fixup` if you want the commit
message to also be changed.
- You can get the hash by looking at `git log` or `git blame`; your IDE can
assist you too.
- Alternatively, if you only know the name of the patch, you can do
`git commit -a --fixup "Subject of Patch name"`.
1. Rebase with autosquash: `git rebase --autosquash -i base`.
This will automatically move your fixup commit to the right place, and you just
need to "save" the changes.
1. Type `./gradlew rebuildPatches` in the root directory;
- This will modify the appropriate patches based on your commits.
1. PR your modified patch file(s) back to this repository.
## Rebasing PRs
Steps to rebase a PR to include the latest changes from `master`.
These steps assume the `origin` remote is your fork of this repository and `upstream` is the official Purpur repository.
1. Pull the latest changes from upstreams master: `git checkout master && git pull upstream master`.
1. Checkout feature/fix branch and rebase on master: `git checkout patch-branch && git rebase master`.
1. Apply updated patches: `./gradlew applyPatches`.
1. If there are conflicts, fix them.
1. If your PR creates new patches instead of modifying exist ones, in both the `Purpur-Server` and `Purpur-API` directories, ensure your newly-created patch is the last commit by either:
* Renaming the patch file with a large 4-digit number in front (e.g. 9999-Patch-to-add-some-new-stuff.patch), and re-applying patches.
* Running `git rebase --interactive base` and moving the commits to the end.
1. Rebuild patches: `./gradlew rebuildPatches`.
1. Commit modified patches.
1. Force push changes: `git push --force`.
## PR Policy
We'll accept changes that make sense. You should be able to justify their existence, along with any maintenance costs that come with them. Remember, these changes will affect everyone who runs Paper, not just you and your server.
While we will fix minor formatting issues, you should stick to the guide below when making and submitting changes.
We'll accept changes that make sense. You should be able to justify their
existence, along with any maintenance costs that come with them. Using
[obfuscation helpers](#obfuscation-helpers) aids in the maintenance costs.
Remember that these changes will affect everyone who runs Purpur, not just you
and your server.
While we will fix minor formatting issues, you should stick to the guide below
when making and submitting changes.
## Formatting
All modifications to non-Purpur files should be marked
- Multi line changes start with `// Purpur start` and end with `// Purpur end`
- You can put a messages with a change if it isn't obvious, like this: `// Purpur start - reason`
- Should generally be about the reason the change was made, what it was before, or what the change is
- Multi-line messages should start with `// Purpur start` and use `/* Multi line message here */` for the message itself
- Single line changes should have `// Purpur` or `// Purpur - reason`
- For example:
All modifications to non-Purpur files should be marked.
- Multi-line changes start with `// Purpur start` and end with `// Purpur end`;
- You can put a comment with an explanation if it isn't obvious, like this:
`// Purpur start - reason`.
- The comments should generally be about the reason the change was made, what
it was before, or what the change is.
- Multi-line messages should start with `// Purpur start` and use `/* Multi
line message here */` for the message itself.
- One-line changes should have `// Purpur` or `// Purpur - reason`.
Here's an example of how to mark changes by Purpur:
```java
entity.getWorld().dontbeStupid(); // Purpur - was beStupid() which is bad
entity.getFriends().forEach(Entity::explode());
entity.getFriends().forEach(Entity::explode);
entity.a();
entity.b();
// Purpur start - use plugin-set spawn
@@ -113,23 +227,39 @@ Location spawnLocation = ((CraftWorld)entity.getWorld()).getSpawnLocation();
entity.getWorld().explode(new BlockPosition(spawnLocation.getX(), spawnLocation.getY(), spawnLocation.getZ()));
// Purpur end
```
- We generally follow usual Java style, or what is programmed into most IDEs and formatters by default
- This is also known as Oracle style
- It is fine to go over 80 lines as long as it doesn't hurt readability
- There are exceptions, especially in Spigot-related files
- When in doubt, use the same style as the surrounding code
We generally follow usual Java style (aka. Oracle style), or what is programmed
into most IDEs and formatters by default. There are a few notes, however:
- It is fine to go over 80 lines as long as it doesn't hurt readability.
There are exceptions, especially in Spigot-related files
- When in doubt or the code around your change is in a clearly different style,
use the same style as the surrounding code.
## Patch Notes
When submitting patches to Purpur, we may ask you to add notes to the patch header.
While we do not require it for all changes, you should add patch notes when the changes you're making are technical or complex.
It is very likely that your patch will remain long after we've all forgotten about the details of your PR, patch notes will help
us maintain it without having to dig back through GitHub history looking for your PR.
These notes should express the intent of your patch, as well as any pertinent technical details we should keep in mind long-term.
Ultimately, they exist to make it easier for us to maintain the patch across major version changes.
When submitting patches to Purpur, we may ask you to add notes to the patch
header. While we do not require it for all changes, you should add patch notes
when the changes you're making are technical, complex, or require an explanation
of some kind. It is very likely that your patch will remain long after we've all
forgotten about the details of your PR; patch notes will help us maintain it
without having to dig back through GitHub history looking for your PR.
If you add a long message to your commit in the Purpur-Server/API repos, the rebuildPatches command will handle these patch
notes automatically as part of generating the patch file. Otherwise if you're careful they can be added by hand (though you should be careful when doing this, and run it through a patch and rebuild cycle once or twice).
These notes should express the intent of your patch, as well as any pertinent
technical details we should keep in mind long-term. Ultimately, they exist to
make it easier for us to maintain the patch across major version changes.
If you add a message to your commit in the `Purpur-Server`/`Purpur-API`
directories, the rebuild patches script will handle these patch notes
automatically as part of generating the patch file. If you are not
extremely careful, you should always just `squash` or `amend` a patch (see the
above sections on modifying patches) and rebuild.
Editing messages and patches by hand is possible, but you should patch and
rebuild afterwards to make sure you did it correctly. This is slower than just
modifying the patches properly after a few times, so you will not really gain
anything but headaches from doing it by hand.
Underneath is an example patch header/note:
```patch
From 02abc033533f70ef3165a97bfda3f5c2fa58633a Mon Sep 17 00:00:00 2001
@@ -157,50 +287,164 @@ index a92bf8967..d0ab87d0f 100644
```
## Obfuscation Helpers
In an effort to make future updates easier on ourselves, Purpur tries to use obfuscation helpers whenever possible. The purpose of these helpers is to make the code more readable. These helpers should be be made as easy to inline as possible by the JVM whenever possible.
An obfuscation helper to get an obfuscated field may be as simple as something like this:
```java
public final int getStuckArrows() { return this.bY(); } // Purpur - OBFHELPER
```
Or it may be as complex as forwarding an entire method so that it can be overridden later:
```java
public boolean be() {
// Purpur start - OBFHELPER
return this.pushedByWater();
}
While rarely needed, obfuscation helpers are sometimes useful when it comes
to unmapped local variables, or poorly named method parameters. In an effort
to make future updates easier on ourselves, Purpur tries to use obfuscation
helpers wherever it makes sense. The purpose of these helpers is to make the
code more readable and maintainable. These helpers should be made easy to
inline by the JVM wherever possible.
public boolean pushedByWater() {
// Purpur end
return true;
}
An example of an obfuscation helper for a local variable:
```java
double d0 = entity.getX(); final double fromX = d0; // Purpur - OBFHELPER
// ...
this.someMethod(fromX); // Purpur
```
While they may not always be done in exactly the same way each time, the general goal is always to improve readability and maintainability, so use your best judgement.
While they may not always be done in exactly the same way, the general goal is
always to improve readability and maintainability. Use your best judgment and do
what fits best in your situation.
## Configuration files
To use a configurable value in your patch, add a new entry in either ```PurpurConfig``` or ```PurpurWorldConfig```. Use the former if a value must remain the same throughout all worlds, or the latter if it can change between worlds. The latter is preferred whenever possible.
### PurpurConfig example:
To use a configurable value in your patch, add a new entry in either the
`PurpurConfig` or `PurpurWorldConfig` classes. Use `PurpurConfig` if a value
must remain the same throughout all worlds, or the latter if it can change
between worlds. World-specific configuration options are preferred whenever
possible.
### PurpurConfig example
```java
public static boolean saveEmptyScoreboardTeams = false;
private static void saveEmptyScoreboardTeams() {
// This is called automatically!
// The name also doesn't matter.
saveEmptyScoreboardTeams = getBoolean("settings.save-empty-scoreboard-teams", false);
}
```
Notice that the field is always public, but the setter is always private. This is important to the way the configuration generation system works. To access this value, reference it as you would any other static value:
Notice that the field is always public, but the setter is always private. This
is important to the way the configuration generation system works. To access
this value, reference it as you would any other static value:
```java
if (!PurpurConfig.saveEmptyScoreboardTeams) {
```
### PurpurWorldConfig example:
It is often preferred that you use the fully qualified name for the
configuration class when accessing it, like so:
`net.pl3x.purpur.PurpurConfig.valueHere`.
If this is not done, a developer for Purpur might fix that for you before
merging, but it's always nice if you make it a habit where you only need 1-2
lines changed.
### PurpurWorldConfig example
```java
public boolean useInhabitedTime = true;
private void useInhabitedTime() {
// This is called automatically!
// The name also doesn't matter.
useInhabitedTime = getBoolean("use-chunk-inhabited-timer", true);
}
```
Again, notice that the field is always public, but the setter is always private. To access this value, you'll need an instance of the ```net.minecraft.World``` object:
Again, notice that the field is always public, but the setter is always private.
To access this value, you'll need an instance of the `net.minecraft.world.level.Level`
object:
```java
return this.world.purpurConfig.useInhabitedTime ? this.w : 0;
return this.level.purpurConfig.useInhabitedTime ? this.inhabitedTime : 0;
```
## Testing API changes
### Using the Purpur Test Plugin
The Purpur project has a `test-plugin` module for easily testing out API changes
and additions. To use the test plugin, enable it in `test-plugin.settings.gradle.kts`,
which will be generated after running Gradle at least once. After this, you can edit
the test plugin, and run a server with the plugin using `./gradlew runDev` (or any
of the other Purpur run tasks).
### Publishing to Maven local (use in external plugins)
To build and install the Purpur APIs and Server to your local Maven repository, do the following:
- Run `./gradlew publishToMavenLocal` in the base directory.
If you use Gradle to build your plugin:
- Add `mavenLocal()` as a repository. Gradle checks repositories in the order they are declared,
so if you also have the Purpur repository added, put the local repository above Purpur's.
- Make sure to remove `mavenLocal()` when you are done testing, see the [Gradle docs](https://docs.gradle.org/current/userguide/declaring_repositories.html#sec:case-for-maven-local)
for more details.
If you use Maven to build your plugin:
- If you later need to use the Purpur-API, you might want to remove the jar
from your local Maven repository.
If you use Windows and don't usually build using WSL, you might not need to
do this.
## Frequently Asked Questions
### I can't find the NMS file I need!
By default, Purpur (and upstream) only import files we make changes to. If you
would like to make changes to a file that isn't present in `Purpur-Server`'s
source directory, you just need to add it to our import script ran during the
patching process.
1. Save (rebuild) any patches you are in the middle of working on! Their
progress will be lost if you do not;
1. Identify the name(s) of the file(s) you want to import.
- A complete list of all possible file names can be found at
`./Purpur-Server/.gradle/caches/paperweight/mc-dev-sources/net/minecraft/`. You might find
[MiniMappingViewer] useful if you need to translate between Mojang and Spigot mapped names.
1. Open the file at `./build-data/dev-imports.txt` and add the name of your file to
the script. Follow the instructions there;
1. Re-patch the server `./gradlew applyPatches`;
1. Edit away!
> ❗ This change is temporary! **DO NOT COMMIT CHANGES TO THIS FILE!**
> Once you have made your changes to the new file, and rebuilt patches, you may
> undo your changes to `dev-imports.txt`.
Any file modified in a patch file gets automatically imported, so you only need
this temporarily to import it to create the first patch.
To undo your changes to the file, type `git checkout build-data/dev-imports.txt`.
### My commit doesn't need a build, what do I do?
Well, quite simple: You add `[ci skip]` to the start of your commit subject.
This case most often applies to changes to files like `README.md`, this very
file (`CONTRIBUTING.md`), the `LICENSE.md` file, and so forth.
### Patching and building is *really* slow, what can I do?
This only applies if you're running Windows. If you're running a prior Windows
release, either update to Windows 10 or move to macOS/Linux/BSD.
In order to speed up patching process on Windows, it's recommended you get WSL
2. This is available in Windows 10 v2004, build 19041 or higher. (You can check
your version by running `winver` in the run window (Windows key + R)). If you're
out of date, update your system with the
[Windows Update Assistant](https://www.microsoft.com/en-us/software-download/windows10).
To set up WSL 2, follow the information here:
<https://docs.microsoft.com/en-us/windows/wsl/install-win10>
You will most likely want to use the Ubuntu apps. Once it's set up, install the
required tools with `sudo apt-get update && sudo apt-get install $TOOL_NAMES
-y`. Replace `$TOOL_NAMES` with the packages found in the
[requirements](#requirements). You can now clone the repository and do
everything like usual.
> ❗ Do not use the `/mnt/` directory in WSL! Instead, mount the WSL directories
> in Windows like described here:
> <https://www.howtogeek.com/426749/how-to-access-your-linux-wsl-files-in-windows-10/>
[MiniMappingViewer]: https://minidigger.github.io/MiniMappingViewer/