Debugging in Singleplayer

Test your datapacks in a local Minecraft world without setting up a server.

Quick Start

1. Find Your Saves Folder

Platform	Path
Windows	%APPDATA%\.minecraft\saves\<world>\datapacks\
macOS	~/Library/Application Support/minecraft/saves/<world>/datapacks/
Linux	~/.minecraft/saves/<world>/datapacks/

2. Compile to World

# Compile directly to your world's datapacks folder
redscript compile game.mcrs -o ~/.minecraft/saves/MyWorld/datapacks/my-game

3. Reload in Game

In Minecraft, run:

/reload

Your datapack is now active!

Watch Mode (Semi-Auto)

Use redscript watch to auto-compile on save:

redscript watch ./src -o ~/Library/Application\ Support/minecraft/saves/TestWorld/datapacks/my-game

Then manually run /reload in-game after each change.

TIP

Keep the Minecraft chat open with /reload ready. After saving your code, just press ↑ Enter to reload.

Helper Script

Create a dev.sh script for convenience:

#!/bin/bash
# dev.sh - Compile and notify

WORLD="TestWorld"
PACK="my-game"
SAVES="$HOME/Library/Application Support/minecraft/saves"

redscript compile src/main.mcrs -o "$SAVES/$WORLD/datapacks/$PACK"

echo "✓ Compiled! Run /reload in Minecraft"

# macOS: Play sound when done
afplay /System/Library/Sounds/Glass.aiff 2>/dev/null

chmod +x dev.sh
./dev.sh

Windows Batch Script

@echo off
REM dev.bat - Compile to world

set WORLD=TestWorld
set PACK=my-game
set SAVES=%APPDATA%\.minecraft\saves

redscript compile src\main.mcrs -o "%SAVES%\%WORLD%\datapacks\%PACK%"

echo Done! Run /reload in Minecraft

Tips

Create a Test World

1. Create a new world in Creative mode
2. Enable cheats
3. Use a flat/void world for faster loading
4. Name it something like "RedScript-Test"

Useful Commands

/reload                    # Reload all datapacks
/datapack list            # List active datapacks
/datapack enable "file/my-game"   # Enable a datapack
/function my-game:start   # Run a function
/gamerule sendCommandFeedback false  # Less chat spam

Debug Output

Add debug messages to trace execution:

fn my_function() {
    say("[DEBUG] my_function called");
    
    let value: int = calculate_something();
    say("[DEBUG] value = " + value);
    
    // ... rest of function
}

Check Function Exists

/function <tab>

Press Tab to autocomplete and verify your functions are loaded.

Limitations

Feature	Singleplayer	Paper Server
Auto-reload	❌ Manual /reload	✅ Hot reload
Tick waiting	❌ No	✅ API
Scoreboard queries	❌ Manual	✅ API
Automated testing	❌ No	✅ Jest integration

For automated testing and hot reload, see Testing with Paper.

Quick Reference

# macOS
redscript compile game.mcrs -o ~/Library/Application\ Support/minecraft/saves/TestWorld/datapacks/game

# Windows (PowerShell)
redscript compile game.mcrs -o "$env:APPDATA\.minecraft\saves\TestWorld\datapacks\game"

# Linux
redscript compile game.mcrs -o ~/.minecraft/saves/TestWorld/datapacks/game