Allow extensions to load other extension's classes, and store extensions by IDs instead of name (#3946)

- the extensionmanagers `extension` method now takes in a extension id instead of name
- extension folders are now created using extension id's
- Extensions can load classes from other extensions now
- Added warning about external class loading
- Wherever applicable: store extensions internally by id instead of name

api/src/main/java/org/geysermc/geyser/api/extension/ExtensionManager.java

@@ -36,13 +36,13 @@ import java.util.Collection;
 public abstract class ExtensionManager {
 
     /**
-     * Gets an extension with the given name.
+     * Gets an extension by the given ID.
      *
-     * @param name the name of the extension
+     * @param id the ID of the extension
-     * @return an extension with the given name
+     * @return an extension with the given ID
      */
     @Nullable
-    public abstract Extension extension(@NonNull String name);
+    public abstract Extension extension(@NonNull String id);
 
     /**
      * Enables the given {@link Extension}.

bootstrap/spigot/src/main/java/org/geysermc/geyser/platform/spigot/GeyserSpigotPlugin.java

@@ -194,7 +194,7 @@ public class GeyserSpigotPlugin extends JavaPlugin implements GeyserBootstrap {
 
                     commandMap.register(extension.description().id(), "geyserext", pluginCommand);
                 } catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException ex) {
-                    this.geyserLogger.error("Failed to construct PluginCommand for extension " + extension.description().name(), ex);
+                    this.geyserLogger.error("Failed to construct PluginCommand for extension " + extension.name(), ex);
                 }
             }
         }

core/src/main/java/org/geysermc/geyser/extension/GeyserExtensionClassLoader.java

@@ -27,6 +27,7 @@ package org.geysermc.geyser.extension;
 
 import it.unimi.dsi.fastutil.objects.Object2ObjectMap;
 import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+import org.geysermc.geyser.GeyserImpl;
 import org.geysermc.geyser.api.extension.Extension;
 import org.geysermc.geyser.api.extension.ExtensionDescription;
 import org.geysermc.geyser.api.extension.exception.InvalidExtensionException;
@@ -39,14 +40,17 @@ import java.nio.file.Path;
 
 public class GeyserExtensionClassLoader extends URLClassLoader {
     private final GeyserExtensionLoader loader;
+    private final ExtensionDescription description;
     private final Object2ObjectMap<String, Class<?>> classes = new Object2ObjectOpenHashMap<>();
+    private boolean warnedForExternalClassAccess;
 
-    public GeyserExtensionClassLoader(GeyserExtensionLoader loader, ClassLoader parent, Path path) throws MalformedURLException {
+    public GeyserExtensionClassLoader(GeyserExtensionLoader loader, ClassLoader parent, Path path, ExtensionDescription description) throws MalformedURLException {
         super(new URL[] { path.toUri().toURL() }, parent);
         this.loader = loader;
+        this.description = description;
     }
 
-    public Extension load(ExtensionDescription description) throws InvalidExtensionException {
+    public Extension load() throws InvalidExtensionException {
         try {
             Class<?> jarClass;
             try {
@@ -76,22 +80,32 @@ public class GeyserExtensionClassLoader extends URLClassLoader {
     }
 
     protected Class<?> findClass(String name, boolean checkGlobal) throws ClassNotFoundException {
-        if (name.startsWith("org.geysermc.geyser.") || name.startsWith("net.minecraft.")) {
-            throw new ClassNotFoundException(name);
-        }
-
         Class<?> result = this.classes.get(name);
         if (result == null) {
+            // Try to find class in current extension
+            try {
                 result = super.findClass(name);
-            if (result == null && checkGlobal) {
+            } catch (ClassNotFoundException ignored) {
+                // If class is not found in current extension, check in the global class loader
+                // This is used for classes that are not in the extension, but are in other extensions
+                if (checkGlobal) {
+                    if (!warnedForExternalClassAccess) {
+                        GeyserImpl.getInstance().getLogger().warning("Extension " + this.description.name() + " loads class " + name + " from an external source. " +
+                                "This can change at any time and break the extension, additionally to potentially causing unexpected behaviour!");
+                        warnedForExternalClassAccess = true;
+                    }
                     result = this.loader.classByName(name);
                 }
+            }
 
             if (result != null) {
+                // If class is found, cache it
                 this.loader.setClass(name, result);
-            }
-
                 this.classes.put(name, result);
+            } else {
+                // If class is not found, throw exception
+                throw new ClassNotFoundException(name);
+            }
         }
         return result;
     }

core/src/main/java/org/geysermc/geyser/extension/GeyserExtensionLoader.java

@@ -66,26 +66,38 @@ public class GeyserExtensionLoader extends ExtensionLoader {
         }
 
         Path parentFile = path.getParent();
-        Path dataFolder = parentFile.resolve(description.name());
+
+        // Extension folders used to be created by name; this changes them to the ID
+        Path oldDataFolder = parentFile.resolve(description.name());
+        Path dataFolder = parentFile.resolve(description.id());
+
+        if (Files.exists(oldDataFolder) && Files.isDirectory(oldDataFolder) && !oldDataFolder.equals(dataFolder)) {
+            try {
+                Files.move(oldDataFolder, dataFolder, StandardCopyOption.REPLACE_EXISTING);
+            } catch (IOException e) {
+                throw new InvalidExtensionException("Failed to move data folder for extension " + description.name(), e);
+            }
+        }
+
         if (Files.exists(dataFolder) && !Files.isDirectory(dataFolder)) {
             throw new InvalidExtensionException("The folder " + dataFolder + " is not a directory and is the data folder for the extension " + description.name() + "!");
         }
 
         final GeyserExtensionClassLoader loader;
         try {
-            loader = new GeyserExtensionClassLoader(this, getClass().getClassLoader(), path);
+            loader = new GeyserExtensionClassLoader(this, getClass().getClassLoader(), path, description);
         } catch (Throwable e) {
             throw new InvalidExtensionException(e);
         }
 
-        this.classLoaders.put(description.name(), loader);
+        this.classLoaders.put(description.id(), loader);
 
-        final Extension extension = loader.load(description);
+        final Extension extension = loader.load();
         return this.setup(extension, description, dataFolder, new GeyserExtensionEventBus(GeyserImpl.getInstance().eventBus(), extension));
     }
 
     private GeyserExtensionContainer setup(Extension extension, GeyserExtensionDescription description, Path dataFolder, ExtensionEventBus eventBus) {
-        GeyserExtensionLogger logger = new GeyserExtensionLogger(GeyserImpl.getInstance().getLogger(), description.name());
+        GeyserExtensionLogger logger = new GeyserExtensionLogger(GeyserImpl.getInstance().getLogger(), description.id());
         return new GeyserExtensionContainer(extension, dataFolder, description, this, logger, eventBus);
     }
 
@@ -152,7 +164,8 @@ public class GeyserExtensionLoader extends ExtensionLoader {
                         GeyserExtensionDescription description = this.extensionDescription(path);
 
                         String name = description.name();
-                        if (extensions.containsKey(name) || extensionManager.extension(name) != null) {
+                        String id = description.id();
+                        if (extensions.containsKey(id) || extensionManager.extension(id) != null) {
                             GeyserImpl.getInstance().getLogger().warning(GeyserLocale.getLocaleStringLog("geyser.extensions.load.duplicate", name, path.toString()));
                             return;
                         }
@@ -169,8 +182,8 @@ public class GeyserExtensionLoader extends ExtensionLoader {
                             return;
                         }
 
-                        extensions.put(name, path);
+                        extensions.put(id, path);
-                        loadedExtensions.put(name, this.loadExtension(path, description));
+                        loadedExtensions.put(id, this.loadExtension(path, description));
                     } catch (Exception e) {
                         GeyserImpl.getInstance().getLogger().error(GeyserLocale.getLocaleStringLog("geyser.extensions.load.failed_with_name", path.getFileName(), path.toAbsolutePath()), e);
                     }

core/src/main/java/org/geysermc/geyser/extension/GeyserExtensionManager.java

@@ -52,8 +52,8 @@ public class GeyserExtensionManager extends ExtensionManager {
     }
 
     @Override
-    public Extension extension(@NonNull String name) {
+    public Extension extension(@NonNull String id) {
-        return this.extensions.get(name);
+        return this.extensions.get(id);
     }
 
     @Override
@@ -83,7 +83,7 @@ public class GeyserExtensionManager extends ExtensionManager {
         if (!extension.isEnabled()) {
             extension.setEnabled(true);
             GeyserImpl.getInstance().eventBus().register(extension, extension);
-            GeyserImpl.getInstance().getLogger().info(GeyserLocale.getLocaleStringLog("geyser.extensions.enable.success", extension.description().name()));
+            GeyserImpl.getInstance().getLogger().info(GeyserLocale.getLocaleStringLog("geyser.extensions.enable.success", extension.name()));
         }
     }
 
@@ -98,7 +98,7 @@ public class GeyserExtensionManager extends ExtensionManager {
             GeyserImpl.getInstance().eventBus().unregisterAll(extension);
 
             extension.setEnabled(false);
-            GeyserImpl.getInstance().getLogger().info(GeyserLocale.getLocaleStringLog("geyser.extensions.disable.success", extension.description().name()));
+            GeyserImpl.getInstance().getLogger().info(GeyserLocale.getLocaleStringLog("geyser.extensions.disable.success", extension.name()));
         }
     }
 
@@ -121,6 +121,6 @@ public class GeyserExtensionManager extends ExtensionManager {
 
     @Override
     public void register(@NonNull Extension extension) {
-        this.extensions.put(extension.name(), extension);
+        this.extensions.put(extension.description().id(), extension);
     }
 }