Fix extension subdependencies not being loaded + Test that J9 modules are supported

build.gradle

@@ -105,6 +105,9 @@ dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.6.2'
     testRuntimeOnly('org.junit.jupiter:junit-jupiter-engine:5.6.2')
 
+    // Only here to ensure J9 module support for extensions and our classloaders
+    testCompileOnly "org.mockito:mockito-core:2.28.2"
+
     // Netty
     api 'io.netty:netty-handler:4.1.58.Final'
     api 'io.netty:netty-codec:4.1.58.Final'

src/main/java/net/minestom/server/extensions/ExtensionManager.java

@@ -2,6 +2,7 @@ package net.minestom.server.extensions;
 
 import com.google.gson.Gson;
 import net.minestom.dependencies.DependencyGetter;
+import net.minestom.dependencies.ResolvedDependency;
 import net.minestom.dependencies.maven.MavenRepository;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.extras.selfmodification.MinestomExtensionClassLoader;
@@ -402,13 +403,13 @@ public class ExtensionManager {
 
                 for (var artifact : externalDependencies.artifacts) {
                     var resolved = getter.get(artifact, dependenciesFolder);
-                    addDependencyFile(resolved.getContentsLocation(), ext);
+                    addDependencyFile(resolved, ext);
                     LOGGER.trace("Dependency of extension {}: {}", ext.getName(), resolved);
                 }
 
                 for (var dependencyName : ext.getDependencies()) {
                     var resolved = getter.get(dependencyName, dependenciesFolder);
-                    addDependencyFile(resolved.getContentsLocation(), ext);
+                    addDependencyFile(resolved, ext);
                     LOGGER.trace("Dependency of extension {}: {}", ext.getName(), resolved);
                 }
             } catch (Exception e) {
@@ -420,9 +421,19 @@ public class ExtensionManager {
         }
     }
 
-    private void addDependencyFile(URL dependency, DiscoveredExtension extension) {
-        extension.files.add(dependency);
-        LOGGER.trace("Added dependency {} to extension {} classpath", dependency.toExternalForm(), extension.getName());
+    private void addDependencyFile(ResolvedDependency dependency, DiscoveredExtension extension) {
+        URL location = dependency.getContentsLocation();
+        extension.files.add(location);
+        LOGGER.trace("Added dependency {} to extension {} classpath", location.toExternalForm(), extension.getName());
+
+        // recurse to add full dependency tree
+        if(!dependency.getSubdependencies().isEmpty()) {
+            LOGGER.trace("Dependency {} has subdependencies, adding...", location.toExternalForm());
+            for(ResolvedDependency sub : dependency.getSubdependencies()) {
+                addDependencyFile(sub, extension);
+            }
+            LOGGER.trace("Dependency {} has had its subdependencies added.", location.toExternalForm());
+        }
     }
 
     /**

src/test/java/improveextensions/MixinIntoMinestomCoreWithJava9ModuleOnClasspath.java

@@ -0,0 +1,43 @@
+package improveextensions;
+
+import net.minestom.server.MinecraftServer;
+import net.minestom.server.extensions.Extension;
+import net.minestom.server.instance.InstanceContainer;
+import net.minestom.server.world.DimensionType;
+import org.junit.jupiter.api.Assertions;
+import org.opentest4j.AssertionFailedError;
+
+import java.util.List;
+import java.util.UUID;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Extensions should be able to use Mixins for classes loaded very early by Minestom (InstanceContainer for instance)
+ */
+public class MixinIntoMinestomCoreWithJava9ModuleOnClasspath extends Extension {
+
+    @Override
+    public void initialize() {
+        // use Mockito only to ensure J9 modules on the classpath are supported
+        List mockedList = mock(List.class);
+        when(mockedList.get(0)).thenReturn("Test");
+        // force load of InstanceContainer class
+        InstanceContainer c = new InstanceContainer(UUID.randomUUID(), DimensionType.OVERWORLD, null);
+        System.out.println(c.toString());
+        try {
+            Assertions.assertTrue(MixinIntoMinestomCore.success, "InstanceContainer must have been mixed in with improveextensions.InstanceContainerMixin");
+            Assertions.assertEquals(1, MinecraftServer.getExtensionManager().getExtensionLoaders().size(), "Only one extension classloader (this extension's) must be active.");
+            Assertions.assertEquals("Test", mockedList.get(0));
+        } catch (AssertionFailedError e) {
+            e.printStackTrace();
+        }
+        MinecraftServer.stopCleanly();
+    }
+
+    @Override
+    public void terminate() {
+        getLogger().info("Terminate extension");
+    }
+}

src/test/resources/improveextensions/j9modules/extension.json

@@ -0,0 +1,14 @@
+{
+  "entrypoint": "improveextensions.MixinIntoMinestomCoreWithJava9ModuleOnClasspath",
+  "name": "MixinIntoMinestomCoreWithJava9ModuleOnClasspath",
+  "codeModifiers": [],
+  "mixinConfig": "mixins.minestomcore.json",
+  "externalDependencies": {
+    "repositories": [
+      {"name": "JCentral", "url": "https://jcenter.bintray.com/"}
+    ],
+    "artifacts": [
+      "org.mockito:mockito-core:2.28.2"
+    ]
+  }
+}

src/test/resources/improveextensions/j9modules/mixins.minestomcore.json

@@ -0,0 +1,10 @@
+{
+  "required": true,
+  "minVersion": "0.8",
+  "package": "improveextensions.mixins",
+  "target": "@env(DEFAULT)",
+  "compatibilityLevel": "JAVA_11",
+  "mixins": [
+    "InstanceContainerMixin"
+  ]
+}