452 lines
20 KiB
Markdown
452 lines
20 KiB
Markdown
Contributing to Paper
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==========================
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PaperMC is happy you're willing to contribute to our projects. We are usually
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very lenient with all submitted PRs, but there are still some guidelines you
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can follow to make the approval process go more smoothly.
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## Use a Personal Fork and not Organization
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Paper will routinely modify your PR, whether it's a quick rebase or to take care
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of any minor nitpicks we might have. Often, it's better for us to solve these
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problems for you than make you go back and forth trying to fix it yourself.
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Unfortunately, if you use an organization for your PR, it prevents Paper from
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modifying it. This requires us to manually merge your PR, resulting in us
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closing the PR instead of marking it as merged.
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We much prefer to have PRs show as merged, so please do not use repositories
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on organizations for PRs.
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See <https://github.com/isaacs/github/issues/1681> for more information on the
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issue.
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## Requirements
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To get started with PRing changes, you'll need the following software, most of
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which can be obtained in (most) package managers such as `apt` (Debian / Ubuntu;
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you will most likely use this for WSL), `homebrew` (macOS / Linux), and more:
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- `git` (package `git` everywhere);
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- A Java 16 or later JDK (packages vary, use Google/DuckDuckGo/etc.).
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- [Adoptium](https://adoptium.net/) has builds for most operating systems.
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- Paper requires JDK 16 to build, however makes use of Gradle's
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[Toolchains](https://docs.gradle.org/current/userguide/toolchains.html)
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feature to allow building with only JRE 8 or later installed. (Gradle will
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automatically provision JDK 16 for compilation if it cannot find an existing
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install).
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If you're on Windows, check
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[the section on WSL](#patching-and-building-is-really-slow-what-can-i-do).
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If you're compiling with Docker, you can use Adoptium's
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[`eclipse-temurin`](https://hub.docker.com/_/eclipse-temurin/) images like so:
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```console
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# docker run -it -v "$(pwd)":/data --rm eclipse-temurin:16.0.2_7-jdk bash
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Pulling image...
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root@abcdefg1234:/# javac -version
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javac 16.0.2
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```
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## Understanding Patches
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Paper is mostly patches and extensions to Spigot. These patches/extensions are
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split into different directories which target certain parts of the code. These
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directories are:
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- `Paper-API` - Modifications to `Spigot-API`/`Bukkit`;
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- `Paper-MojangAPI` - An API for [Mojang's Brigadier](https://github.com/Mojang/brigadier);
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- `Paper-Server` - Modifications to `Spigot`/`CraftBukkit`.
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Because the entire structure is based on patches and git, a basic understanding
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of how to use git is required. A basic tutorial can be found here:
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<https://git-scm.com/docs/gittutorial>.
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Assuming you have already forked the repository:
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1. Clone your fork to your local machine;
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2. Type `./gradlew applyPatches` in a terminal to apply the changes from upstream.
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On Windows, leave out the `./` at the beginning for all `gradlew` commands;
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3. cd into `Paper-Server` for server changes, and `Paper-API` for API changes.
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<!--You can also run `./paper server` or `./paper api` for these same directories
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respectively.
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1. You can also run `./paper setup`, which allows you to type `paper <command>`
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from anywhere in the Paper structure in most cases.-->
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`Paper-Server` and `Paper-API` aren't git repositories in the traditional sense:
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- `base` points to the unmodified source before Paper patches have been applied.
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- Each commit after `base` is a patch.
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## Adding Patches
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Adding patches to Paper is very simple:
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1. Modify `Paper-Server` and/or `Paper-API` with the appropriate changes;
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1. Type `git add .` inside these directories to add your changes;
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1. Run `git commit` with the desired patch message;
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1. Run `./gradlew rebuildPatches` in the main directory to convert your commit into a new
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patch;
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1. PR the generated patch file(s) back to this repository.
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Your commit will be converted into a patch that you can then PR into Paper.
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> ❗ Please note that if you have some specific implementation detail you'd like
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> to document, you should do so in the patch message *or* in comments.
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## Modifying Patches
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Modifying previous patches is a bit more complex:
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### Method 1
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This method works by temporarily resetting your `HEAD` to the desired commit to
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edit it using `git rebase`.
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> ❗ While in the middle of an edit, you will not be able to compile unless you
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> *also* reset the opposing module(s) to a related commit. In the API's case,
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> you must reset the Server, and reset the API if you're editing the Server.
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> Note also that either module _may_ not compile when doing so. This is not
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> ideal nor intentional, but it happens. Feel free to fix this in a PR to us!
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1. If you have changes you are working on, type `git stash` to store them for
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later;
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- You can type `git stash pop` to get them back at any point.
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1. Type `git rebase -i base`;
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- It should show something like
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[this](https://gist.github.com/zachbr/21e92993cb99f62ffd7905d7b02f3159) in
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the text editor you get.
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- If your editor does not have a "menu" at the bottom, you're using `vim`.
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If you don't know how to use `vim` and don't want to
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learn, enter `:q!` and press enter. Before redoing this step, do
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`export EDITOR=nano` for an easier editor to use.
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1. Replace `pick` with `edit` for the commit/patch you want to modify, and
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"save" the changes;
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- Only do this for **one** commit at a time.
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1. Make the changes you want to make to the patch;
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1. Type `git add .` to add your changes;
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1. Type `git commit --amend` to commit;
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- **Make sure to add `--amend`** or else a new patch will be created.
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- You can also modify the commit message and author here.
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1. Type `git rebase --continue` to finish rebasing;
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1. Type `./gradlew rebuildPatches` in the root directory;
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- This will modify the appropriate patches based on your commits.
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1. PR your modified patch file(s) back to this repository.
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### Method 2 - Fixup commits
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If you are simply editing a more recent commit or your change is small, simply
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making the change at HEAD and then moving the commit after you have tested it
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may be easier.
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This method has the benefit of being able to compile to test your change without
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messing with your HEADs.
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#### Manual method
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1. Make your change while at HEAD;
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1. Make a temporary commit. You don't need to make a message for this;
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1. Type `git rebase -i base`, move (cut) your temporary commit and
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move it under the line of the patch you wish to modify;
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1. Change the `pick` to the appropriate action:
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1. `f`/`fixup`: Merge your changes into the patch without touching the
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message.
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1. `s`/`squash`: Merge your changes into the patch and use your commit message
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and subject.
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1. Type `./gradlew rebuildPatches` in the root directory;
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- This will modify the appropriate patches based on your commits.
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1. PR your modified patch file(s) back to this repository.
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#### Automatic method
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1. Make your change while at HEAD;
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1. Make a fixup commit. `git commit -a --fixup <hashOfPatchToFix>`;
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- You can also use `--squash` instead of `--fixup` if you want the commit
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message to also be changed.
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- You can get the hash by looking at `git log` or `git blame`; your IDE can
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assist you too.
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- Alternatively, if you only know the name of the patch, you can do
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`git commit -a --fixup "Subject of Patch name"`.
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1. Rebase with autosquash: `git rebase --autosquash -i base`.
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This will automatically move your fixup commit to the right place, and you just
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need to "save" the changes.
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1. Type `./gradlew rebuildPatches` in the root directory;
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- This will modify the appropriate patches based on your commits.
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1. PR your modified patch file(s) back to this repository.
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## Rebasing PRs
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Steps to rebase a PR to include the latest changes from `master`.
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These steps assume the `origin` remote is your fork of this repository and `upstream` is the official PaperMC repository.
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1. Pull the latest changes from upstreams master: `git checkout master && git pull upstream master`.
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1. Checkout feature/fix branch and rebase on master: `git checkout patch-branch && git rebase master`.
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1. Apply updated patches: `./gradlew applyPatches`.
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1. If there are conflicts, fix them.
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1. If your PR creates new patches instead of modifying exist ones, in both the `Paper-Server` and `Paper-API` directories, ensure your newly-created patch is the last commit by either:
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* 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.
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* Running `git rebase --interactive base` and moving the commits to the end.
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1. Rebuild patches: `./gradlew rebuildPatches`.
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1. Commit modified patches.
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1. Force push changes: `git push --force`.
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## PR Policy
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We'll accept changes that make sense. You should be able to justify their
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existence, along with any maintenance costs that come with them. Using
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[obfuscation helpers](#obfuscation-helpers) aids in the maintenance costs.
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Remember that these changes will affect everyone who runs Paper, not just you
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and your server.
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While we will fix minor formatting issues, you should stick to the guide below
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when making and submitting changes.
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## Formatting
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All modifications to non-Paper files should be marked.
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- Multi-line changes start with `// Paper start` and end with `// Paper end`;
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- You can put a comment with an explanation if it isn't obvious, like this:
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`// Paper start - reason`.
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- The comments should generally be about the reason the change was made, what
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it was before, or what the change is.
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- Multi-line messages should start with `// Paper start` and use `/* Multi
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line message here */` for the message itself.
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- One-line changes should have `// Paper` or `// Paper - reason`.
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Here's an example of how to mark changes by Paper:
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```java
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entity.getWorld().dontbeStupid(); // Paper - was beStupid() which is bad
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entity.getFriends().forEach(Entity::explode);
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entity.a();
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entity.b();
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// Paper start - use plugin-set spawn
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// entity.getWorld().explode(entity.getWorld().getSpawn());
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Location spawnLocation = ((CraftWorld)entity.getWorld()).getSpawnLocation();
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entity.getWorld().explode(new BlockPosition(spawnLocation.getX(), spawnLocation.getY(), spawnLocation.getZ()));
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// Paper end
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```
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We generally follow usual Java style (aka. Oracle style), or what is programmed
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into most IDEs and formatters by default. There are a few notes, however:
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- It is fine to go over 80 lines as long as it doesn't hurt readability.
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There are exceptions, especially in Spigot-related files
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- When in doubt or the code around your change is in a clearly different style,
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use the same style as the surrounding code.
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## Patch Notes
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When submitting patches to Paper, we may ask you to add notes to the patch
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header. While we do not require it for all changes, you should add patch notes
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when the changes you're making are technical, complex, or require an explanation
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of some kind. It is very likely that your patch will remain long after we've all
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forgotten about the details of your PR; patch notes will help us maintain it
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without having to dig back through GitHub history looking for your PR.
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These notes should express the intent of your patch, as well as any pertinent
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technical details we should keep in mind long-term. Ultimately, they exist to
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make it easier for us to maintain the patch across major version changes.
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If you add a message to your commit in the `Paper-Server`/`Paper-API`
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directories, the rebuild patches script will handle these patch notes
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automatically as part of generating the patch file. If you are not
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extremely careful, you should always just `squash` or `amend` a patch (see the
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above sections on modifying patches) and rebuild.
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Editing messages and patches by hand is possible, but you should patch and
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rebuild afterwards to make sure you did it correctly. This is slower than just
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modifying the patches properly after a few times, so you will not really gain
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anything but headaches from doing it by hand.
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Underneath is an example patch header/note:
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```patch
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From 02abc033533f70ef3165a97bfda3f5c2fa58633a Mon Sep 17 00:00:00 2001
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From: Shane Freeder <theboyetronic@gmail.com>
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Date: Sun, 15 Oct 2017 00:29:07 +0100
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Subject: [PATCH] revert serverside behavior of keepalives
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This patch intends to bump up the time that a client has to reply to the
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server back to 30 seconds as per pre 1.12.2, which allowed clients
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more than enough time to reply potentially allowing them to be less
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tempermental due to lag spikes on the network thread, e.g. that caused
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by plugins that are interacting with netty.
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We also add a system property to allow people to tweak how long the server
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will wait for a reply. There is a compromise here between lower and higher
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values, lower values will mean that dead connections can be closed sooner,
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whereas higher values will make this less sensitive to issues such as spikes
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from networking or during connections flood of chunk packets on slower clients,
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at the cost of dead connections being kept open for longer.
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diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
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index a92bf8967..d0ab87d0f 100644
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--- a/src/main/java/net/minecraft/server/PlayerConnection.java
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+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
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```
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## Obfuscation Helpers
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While rarely needed, obfuscation helpers are sometimes useful when it comes
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to unmapped local variables, or poorly named method parameters. In an effort
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to make future updates easier on ourselves, Paper tries to use obfuscation
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helpers wherever it makes sense. The purpose of these helpers is to make the
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code more readable and maintainable. These helpers should be made easy to
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inline by the JVM wherever possible.
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An example of an obfuscation helper for a local variable:
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```java
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double d0 = entity.getX(); final double fromX = d0; // Paper - OBFHELPER
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// ...
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this.someMethod(fromX); // Paper
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```
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While they may not always be done in exactly the same way, the general goal is
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always to improve readability and maintainability. Use your best judgment and do
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what fits best in your situation.
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## Configuration files
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To use a configurable value in your patch, add a new entry in either the
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`PaperConfig` or `PaperWorldConfig` classes. Use `PaperConfig` if a value
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must remain the same throughout all worlds, or the latter if it can change
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between worlds. World-specific configuration options are preferred whenever
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possible.
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### PaperConfig example
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```java
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public static boolean saveEmptyScoreboardTeams = false;
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private static void saveEmptyScoreboardTeams() {
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// This is called automatically!
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// The name also doesn't matter.
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saveEmptyScoreboardTeams = getBoolean("settings.save-empty-scoreboard-teams", false);
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}
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```
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Notice that the field is always public, but the setter is always private. This
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is important to the way the configuration generation system works. To access
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this value, reference it as you would any other static value:
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```java
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if (!PaperConfig.saveEmptyScoreboardTeams) {
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```
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It is often preferred that you use the fully qualified name for the
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configuration class when accessing it, like so:
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`com.destroystokyo.paper.PaperConfig.valueHere`.
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If this is not done, a developer for Paper might fix that for you before
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merging, but it's always nice if you make it a habit where you only need 1-2
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lines changed.
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### PaperWorldConfig example
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```java
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public boolean useInhabitedTime = true;
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private void useInhabitedTime() {
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// This is called automatically!
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// The name also doesn't matter.
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useInhabitedTime = getBoolean("use-chunk-inhabited-timer", true);
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}
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```
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Again, notice that the field is always public, but the setter is always private.
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To access this value, you'll need an instance of the `net.minecraft.world.level.Level`
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object:
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```java
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return this.level.paperConfig.useInhabitedTime ? this.inhabitedTime : 0;
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```
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## Testing API changes
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### Using the Paper Test Plugin
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The Paper project has a `test-plugin` module for easily testing out API changes
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and additions. To use the test plugin, enable it in `test-plugin.settings.gradle.kts`,
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which will be generated after running Gradle at least once. After this, you can edit
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the test plugin, and run a server with the plugin using `./gradlew runDev` (or any
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of the other Paper run tasks).
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### Publishing to Maven local (use in external plugins)
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To build and install the Paper APIs and Server to your local Maven repository, do the following:
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- Run `./gradlew publishToMavenLocal` in the base directory.
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If you use Gradle to build your plugin:
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- Add `mavenLocal()` as a repository. Gradle checks repositories in the order they are declared,
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so if you also have the Paper repository added, put the local repository above Paper's.
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- 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)
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for more details.
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If you use Maven to build your plugin:
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- If you later need to use the Paper-API, you might want to remove the jar
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from your local Maven repository.
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If you use Windows and don't usually build using WSL, you might not need to
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do this.
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## Frequently Asked Questions
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### I can't find the NMS file I need!
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By default, Paper (and upstream) only import files we make changes to. If you
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would like to make changes to a file that isn't present in `Paper-Server`'s
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source directory, you just need to add it to our import script ran during the
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patching process.
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1. Save (rebuild) any patches you are in the middle of working on! Their
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progress will be lost if you do not;
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1. Identify the name(s) of the file(s) you want to import.
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- A complete list of all possible file names can be found at
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`./Paper-Server/.gradle/caches/paperweight/mc-dev-sources/net/minecraft/`. You might find
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[MiniMappingViewer] useful if you need to translate between Mojang and Spigot mapped names.
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1. Open the file at `./build-data/dev-imports.txt` and add the name of your file to
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the script. Follow the instructions there;
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1. Re-patch the server `./gradlew applyPatches`;
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1. Edit away!
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> ❗ This change is temporary! **DO NOT COMMIT CHANGES TO THIS FILE!**
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> Once you have made your changes to the new file, and rebuilt patches, you may
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> undo your changes to `dev-imports.txt`.
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Any file modified in a patch file gets automatically imported, so you only need
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this temporarily to import it to create the first patch.
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To undo your changes to the file, type `git checkout build-data/dev-imports.txt`.
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### My commit doesn't need a build, what do I do?
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Well, quite simple: You add `[ci skip]` to the start of your commit subject.
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This case most often applies to changes to files like `README.md`, this very
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file (`CONTRIBUTING.md`), the `LICENSE.md` file, and so forth.
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### Patching and building is *really* slow, what can I do?
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This only applies if you're running Windows. If you're running a prior Windows
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release, either update to Windows 10 or move to macOS/Linux/BSD.
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In order to speed up patching process on Windows, it's recommended you get WSL
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2. This is available in Windows 10 v2004, build 19041 or higher. (You can check
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your version by running `winver` in the run window (Windows key + R)). If you're
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out of date, update your system with the
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[Windows Update Assistant](https://www.microsoft.com/en-us/software-download/windows10).
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To set up WSL 2, follow the information here:
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<https://docs.microsoft.com/en-us/windows/wsl/install-win10>
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You will most likely want to use the Ubuntu apps. Once it's set up, install the
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required tools with `sudo apt-get update && sudo apt-get install $TOOL_NAMES
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-y`. Replace `$TOOL_NAMES` with the packages found in the
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[requirements](#requirements). You can now clone the repository and do
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everything like usual.
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> ❗ Do not use the `/mnt/` directory in WSL! Instead, mount the WSL directories
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> in Windows like described here:
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> <https://www.howtogeek.com/426749/how-to-access-your-linux-wsl-files-in-windows-10/>
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[MiniMappingViewer]: https://minidigger.github.io/MiniMappingViewer/
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