jso: support varargs in exported classes and modules

classlib/src/main/java/org/teavm/classlib/impl/AnnotationVirtualMethods.java

@@ -15,15 +15,15 @@
  */
 package org.teavm.classlib.impl;
 
-import org.teavm.backend.javascript.spi.VirtualMethodContributor;
+import org.teavm.backend.javascript.spi.MethodContributor;
-import org.teavm.backend.javascript.spi.VirtualMethodContributorContext;
+import org.teavm.backend.javascript.spi.MethodContributorContext;
 import org.teavm.model.ClassReader;
 import org.teavm.model.MethodReference;
 import org.teavm.platform.PlatformAnnotationProvider;
 
-public class AnnotationVirtualMethods implements VirtualMethodContributor {
+public class AnnotationVirtualMethods implements MethodContributor {
     @Override
-    public boolean isVirtual(VirtualMethodContributorContext context, MethodReference methodRef) {
+    public boolean isContributing(MethodContributorContext context, MethodReference methodRef) {
         ClassReader cls = context.getClassSource().get(methodRef.getClassName());
         if (cls == null || !cls.getInterfaces().contains(PlatformAnnotationProvider.class.getName())) {
             return false;

core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java

@@ -60,8 +60,8 @@ import org.teavm.backend.javascript.spi.GeneratedBy;
 import org.teavm.backend.javascript.spi.Generator;
 import org.teavm.backend.javascript.spi.InjectedBy;
 import org.teavm.backend.javascript.spi.Injector;
-import org.teavm.backend.javascript.spi.VirtualMethodContributor;
+import org.teavm.backend.javascript.spi.MethodContributor;
-import org.teavm.backend.javascript.spi.VirtualMethodContributorContext;
+import org.teavm.backend.javascript.spi.MethodContributorContext;
 import org.teavm.backend.javascript.templating.JavaScriptTemplateFactory;
 import org.teavm.cache.EmptyMethodNodeCache;
 import org.teavm.cache.MethodNodeCache;
@@ -122,7 +122,8 @@ public class JavaScriptTarget implements TeaVMTarget, TeaVMJavaScriptHost {
     private DebugInformationEmitter debugEmitter;
     private MethodNodeCache astCache = EmptyMethodNodeCache.INSTANCE;
     private final Set<MethodReference> asyncMethods = new HashSet<>();
-    private List<VirtualMethodContributor> customVirtualMethods = new ArrayList<>();
+    private List<MethodContributor> customVirtualMethods = new ArrayList<>();
+    private List<MethodContributor> forcedFunctionMethods = new ArrayList<>();
     private boolean strict;
     private BoundCheckInsertion boundCheckInsertion = new BoundCheckInsertion();
     private NullCheckInsertion nullCheckInsertion = new NullCheckInsertion(NullCheckFilter.EMPTY);
@@ -366,11 +367,13 @@ public class JavaScriptTarget implements TeaVMTarget, TeaVMJavaScriptHost {
             debugEmitterToUse = new DummyDebugInformationEmitter();
         }
 
-        var virtualMethodContributorContext = new VirtualMethodContributorContextImpl(classes);
+        var methodContributorContext = new MethodContributorContextImpl(classes);
         RenderingContext renderingContext = new RenderingContext(debugEmitterToUse,
                 controller.getUnprocessedClassSource(), classes,
                 controller.getClassLoader(), controller.getServices(), controller.getProperties(), naming,
-                controller.getDependencyInfo(), m -> isVirtual(virtualMethodContributorContext, m),
+                controller.getDependencyInfo(),
+                m -> isVirtual(methodContributorContext, m),
+                m -> isForcedFunction(methodContributorContext, m),
                 controller.getClassInitializerInfo(), strict
         ) {
             @Override
@@ -804,31 +807,45 @@ public class JavaScriptTarget implements TeaVMTarget, TeaVMJavaScriptHost {
     }
 
     @Override
-    public void addVirtualMethods(VirtualMethodContributor virtualMethods) {
+    public void addVirtualMethods(MethodContributor virtualMethods) {
         customVirtualMethods.add(virtualMethods);
     }
 
+    @Override
+    public void addForcedFunctionMethods(MethodContributor forcedFunctionMethods) {
+        this.forcedFunctionMethods.add(forcedFunctionMethods);
+    }
+
     @Override
     public boolean isAsyncSupported() {
         return true;
     }
 
-    private boolean isVirtual(VirtualMethodContributorContext context, MethodReference method) {
+    private boolean isVirtual(MethodContributorContext context, MethodReference method) {
         if (controller.isVirtual(method)) {
             return true;
         }
-        for (VirtualMethodContributor predicate : customVirtualMethods) {
+        for (MethodContributor predicate : customVirtualMethods) {
-            if (predicate.isVirtual(context, method)) {
+            if (predicate.isContributing(context, method)) {
                 return true;
             }
         }
         return false;
     }
 
-    static class VirtualMethodContributorContextImpl implements VirtualMethodContributorContext {
+    private boolean isForcedFunction(MethodContributorContext context, MethodReference method) {
+        for (var predicate : forcedFunctionMethods) {
+            if (predicate.isContributing(context, method)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private static class MethodContributorContextImpl implements MethodContributorContext {
         private ClassReaderSource classSource;
 
-        VirtualMethodContributorContextImpl(ClassReaderSource classSource) {
+        MethodContributorContextImpl(ClassReaderSource classSource) {
             this.classSource = classSource;
         }
 

core/src/main/java/org/teavm/backend/javascript/TeaVMJavaScriptHost.java

@@ -18,7 +18,7 @@ package org.teavm.backend.javascript;
 import java.util.function.Function;
 import org.teavm.backend.javascript.spi.Generator;
 import org.teavm.backend.javascript.spi.Injector;
-import org.teavm.backend.javascript.spi.VirtualMethodContributor;
+import org.teavm.backend.javascript.spi.MethodContributor;
 import org.teavm.model.MethodReference;
 import org.teavm.vm.spi.RendererListener;
 import org.teavm.vm.spi.TeaVMHostExtension;
@@ -34,5 +34,7 @@ public interface TeaVMJavaScriptHost extends TeaVMHostExtension {
 
     void add(RendererListener listener);
 
-    void addVirtualMethods(VirtualMethodContributor virtualMethods);
+    void addVirtualMethods(MethodContributor virtualMethods);
+
+    void addForcedFunctionMethods(MethodContributor forcedFunctionMethods);
 }

core/src/main/java/org/teavm/backend/javascript/rendering/MethodBodyRenderer.java

@@ -93,12 +93,16 @@ public class MethodBodyRenderer implements MethodNodeVisitor, GeneratorContext {
     }
 
     public void renderParameters(MethodReference reference, Set<ElementModifier> modifiers) {
+        renderParameters(reference, modifiers, false);
+    }
+
+    public void renderParameters(MethodReference reference, Set<ElementModifier> modifiers, boolean forceParentheses) {
         int startParam = 0;
         if (modifiers.contains(ElementModifier.STATIC)) {
             startParam = 1;
         }
         var count = reference.parameterCount() - startParam + 1;
-        if (count != 1) {
+        if (count != 1 || forceParentheses) {
             writer.append("(");
         }
         for (int i = startParam; i <= reference.parameterCount(); ++i) {
@@ -107,7 +111,7 @@ public class MethodBodyRenderer implements MethodNodeVisitor, GeneratorContext {
             }
             writer.append(statementRenderer.variableName(i));
         }
-        if (count != 1) {
+        if (count != 1 || forceParentheses) {
             writer.append(")");
         }
     }

core/src/main/java/org/teavm/backend/javascript/rendering/Renderer.java

@@ -372,8 +372,13 @@ public class Renderer implements RenderingManager {
             if (!filterMethod(method)) {
                 continue;
             }
-            writer.startVariableDeclaration();
+            var isFunction = context.isForcedFunction(method.getReference());
-            renderBody(method, decompiler);
+            if (isFunction) {
+                writer.startFunctionDeclaration();
+            } else {
+                writer.startVariableDeclaration();
+            }
+            renderBody(method, decompiler, isFunction);
             writer.endDeclaration();
             if (needsInitializers && !method.hasModifier(ElementModifier.STATIC)
                     && method.getName().equals("<init>")) {
@@ -381,7 +386,6 @@ public class Renderer implements RenderingManager {
             }
         }
 
-
         writer.emitClass(null);
     }
 
@@ -781,7 +785,12 @@ public class Renderer implements RenderingManager {
     }
 
     private void emitVirtualFunctionWrapper(MethodReference method) {
-        if (method.parameterCount() <= 4) {
+        var forced = context.isForcedFunction(method);
+        if (forced) {
+            writer.appendFunction("$rt_wrapFunctionVararg").append("(").appendMethod(method).append(")");
+            return;
+        }
+        if (method.parameterCount() <= 4 && !forced) {
             writer.appendFunction("$rt_wrapFunction" + method.parameterCount());
             writer.append("(").appendMethod(method).append(")");
             return;
@@ -810,22 +819,22 @@ public class Renderer implements RenderingManager {
         writer.append(");").ws().append("}");
     }
 
-    private void renderBody(MethodHolder method, Decompiler decompiler) {
+    private void renderBody(MethodHolder method, Decompiler decompiler, boolean isFunction) {
         MethodReference ref = method.getReference();
         writer.emitMethod(ref.getDescriptor());
 
         writer.appendMethod(ref);
         if (method.hasModifier(ElementModifier.NATIVE)) {
-            renderNativeBody(method, classSource);
+            renderNativeBody(method, classSource, isFunction);
         } else {
-            renderRegularBody(method, decompiler);
+            renderRegularBody(method, decompiler, isFunction);
         }
 
         writer.outdent().append("}");
         writer.emitMethod(null);
     }
 
-    private void renderNativeBody(MethodHolder method, ClassReaderSource classes) {
+    private void renderNativeBody(MethodHolder method, ClassReaderSource classes, boolean isFunction) {
         var reference = method.getReference();
         var generator = generators.get(reference);
         if (generator == null) {
@@ -841,7 +850,7 @@ public class Renderer implements RenderingManager {
         }
 
         var async = asyncMethods.contains(reference);
-        renderMethodPrologue(reference, method.getModifiers());
+        renderMethodPrologue(reference, method.getModifiers(), isFunction);
         methodBodyRenderer.renderNative(generator, async, reference);
         threadLibraryUsed |= methodBodyRenderer.isThreadLibraryUsed();
     }
@@ -895,7 +904,7 @@ public class Renderer implements RenderingManager {
         }
     }
 
-    private void renderRegularBody(MethodHolder method, Decompiler decompiler) {
+    private void renderRegularBody(MethodHolder method, Decompiler decompiler, boolean isFunction) {
         MethodReference reference = method.getReference();
         MethodNode node;
         var async = asyncMethods.contains(reference);
@@ -907,14 +916,17 @@ public class Renderer implements RenderingManager {
         }
 
         methodBodyRenderer.setCurrentMethod(node);
-        renderMethodPrologue(method.getReference(), method.getModifiers());
+        renderMethodPrologue(method.getReference(), method.getModifiers(), isFunction);
         methodBodyRenderer.render(node, async);
         threadLibraryUsed |= methodBodyRenderer.isThreadLibraryUsed();
     }
 
-    private void renderMethodPrologue(MethodReference reference, Set<ElementModifier> modifier) {
+    private void renderMethodPrologue(MethodReference reference, Set<ElementModifier> modifier, boolean isFunction) {
-        methodBodyRenderer.renderParameters(reference, modifier);
+        methodBodyRenderer.renderParameters(reference, modifier, isFunction);
-        writer.sameLineWs().append("=>").ws().append("{").indent().softNewLine();
+        if (!isFunction) {
+            writer.sameLineWs().append("=>");
+        }
+        writer.ws().append("{").indent().softNewLine();
     }
 
     private AstCacheEntry decompileRegular(Decompiler decompiler, MethodHolder method) {

core/src/main/java/org/teavm/backend/javascript/rendering/RenderingContext.java

@@ -51,6 +51,7 @@ public abstract class RenderingContext {
     private NamingStrategy naming;
     private DependencyInfo dependencyInfo;
     private Predicate<MethodReference> virtualPredicate;
+    private Predicate<MethodReference> forcedFunctionPredicate;
     private final Map<String, Integer> stringPoolMap = new HashMap<>();
     private final List<String> stringPool = new ArrayList<>();
     private final List<String> readonlyStringPool = Collections.unmodifiableList(stringPool);
@@ -63,7 +64,9 @@ public abstract class RenderingContext {
             ClassReaderSource initialClassSource, ListableClassReaderSource classSource,
             ClassLoader classLoader, ServiceRepository services, Properties properties,
             NamingStrategy naming, DependencyInfo dependencyInfo,
-            Predicate<MethodReference> virtualPredicate, ClassInitializerInfo classInitializerInfo,
+            Predicate<MethodReference> virtualPredicate,
+            Predicate<MethodReference> forcedFunctionPredicate,
+            ClassInitializerInfo classInitializerInfo,
             boolean strict) {
         this.debugEmitter = debugEmitter;
         this.initialClassSource = initialClassSource;
@@ -74,6 +77,7 @@ public abstract class RenderingContext {
         this.naming = naming;
         this.dependencyInfo = dependencyInfo;
         this.virtualPredicate = virtualPredicate;
+        this.forcedFunctionPredicate = forcedFunctionPredicate;
         this.classInitializerInfo = classInitializerInfo;
         this.strict = strict;
     }
@@ -118,6 +122,10 @@ public abstract class RenderingContext {
         return virtualPredicate.test(method);
     }
 
+    public boolean isForcedFunction(MethodReference method) {
+        return forcedFunctionPredicate.test(method);
+    }
+
     public boolean isDynamicInitializer(String className) {
         return classInitializerInfo.isDynamicInitializer(className);
     }

core/src/main/java/org/teavm/backend/javascript/spi/MethodContributor.java

@@ -17,6 +17,6 @@ package org.teavm.backend.javascript.spi;
 
 import org.teavm.model.MethodReference;
 
-public interface VirtualMethodContributor {
+public interface MethodContributor {
-    boolean isVirtual(VirtualMethodContributorContext context, MethodReference methodRef);
+    boolean isContributing(MethodContributorContext context, MethodReference methodRef);
 }

core/src/main/java/org/teavm/backend/javascript/spi/MethodContributorContext.java

@@ -17,6 +17,6 @@ package org.teavm.backend.javascript.spi;
 
 import org.teavm.model.ClassReaderSource;
 
-public interface VirtualMethodContributorContext {
+public interface MethodContributorContext {
     ClassReaderSource getClassSource();
 }

core/src/main/java/org/teavm/model/ClassReaderSource.java

@@ -119,4 +119,12 @@ public interface ClassReaderSource {
     default Optional<Boolean> isSuperType(String superType, String subType) {
         return ClassReaderSourceHelper.isSuperType(this, superType, subType);
     }
+
+    default MethodReader getMethod(MethodReference ref) {
+        var cls = get(ref.getClassName());
+        if (cls == null) {
+            return null;
+        }
+        return cls.getMethod(ref.getDescriptor());
+    }
 }

core/src/main/resources/org/teavm/backend/javascript/runtime.js

@@ -40,6 +40,12 @@ let $rt_wrapFunction3 = f => function(p1, p2, p3) {
 let $rt_wrapFunction4 = f => function(p1, p2, p3, p4) {
     return f(this, p1, p2, p3, p4);
 }
+let $rt_wrapFunctionVararg = f => function() {
+    let array = new teavm_globals.Array();
+    array.push(this);
+    Array.prototype.push.apply(array, arguments);
+    return f.apply(null, array);
+}
 let $rt_threadStarter = f => function() {
     let args = teavm_globals.Array.prototype.slice.apply(arguments);
     $rt_startThread(function() {
@@ -110,4 +116,6 @@ let $rt_setThread = t => {
 
 let $rt_apply = (instance, method, args) => instance[method].apply(instance, args);
 
-let $rt_apply_topLevel = (method, args) => method.apply(null, args);
+let $rt_apply_topLevel = (method, args) => method.apply(null, args);
+
+let $rt_skip = (array, count) => count === 0 ? array : Array.prototype.slice.call(array, count);

jso/impl/src/main/java/org/teavm/jso/impl/JS.java

@@ -716,4 +716,8 @@ final class JS {
     @InjectedBy(JSNativeInjector.class)
     @NoSideEffects
     public static native JSObject throwCCEIfFalse(boolean value, JSObject o);
+
+    @InjectedBy(JSNativeInjector.class)
+    @NoSideEffects
+    public static native JSObject argumentsBeginningAt(int index);
 }

jso/impl/src/main/java/org/teavm/jso/impl/JSAliasRenderer.java

@@ -20,8 +20,8 @@ import java.util.Map;
 import java.util.function.Predicate;
 import org.teavm.backend.javascript.codegen.SourceWriter;
 import org.teavm.backend.javascript.rendering.RenderingManager;
-import org.teavm.backend.javascript.spi.VirtualMethodContributor;
+import org.teavm.backend.javascript.spi.MethodContributor;
-import org.teavm.backend.javascript.spi.VirtualMethodContributorContext;
+import org.teavm.backend.javascript.spi.MethodContributorContext;
 import org.teavm.jso.JSClass;
 import org.teavm.model.AnnotationReader;
 import org.teavm.model.ClassReader;
@@ -35,7 +35,7 @@ import org.teavm.model.MethodReference;
 import org.teavm.vm.BuildTarget;
 import org.teavm.vm.spi.RendererListener;
 
-class JSAliasRenderer implements RendererListener, VirtualMethodContributor {
+class JSAliasRenderer implements RendererListener, MethodContributor {
     private static String variableChars = "abcdefghijklmnopqrstuvwxyz";
     private SourceWriter writer;
     private ListableClassReaderSource classSource;
@@ -389,7 +389,7 @@ class JSAliasRenderer implements RendererListener, VirtualMethodContributor {
     }
 
     @Override
-    public boolean isVirtual(VirtualMethodContributorContext context, MethodReference methodRef) {
+    public boolean isContributing(MethodContributorContext context, MethodReference methodRef) {
         ClassReader classReader = context.getClassSource().get(methodRef.getClassName());
         if (classReader == null) {
             return false;

jso/impl/src/main/java/org/teavm/jso/impl/JSExportedMethodAsFunction.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.jso.impl;
+
+import org.teavm.backend.javascript.spi.MethodContributor;
+import org.teavm.backend.javascript.spi.MethodContributorContext;
+import org.teavm.model.MethodReference;
+
+public class JSExportedMethodAsFunction implements MethodContributor {
+    @Override
+    public boolean isContributing(MethodContributorContext context, MethodReference methodRef) {
+        var method = context.getClassSource().getMethod(methodRef);
+        if (method != null) {
+            if (method.getAnnotations().get(JSVararg.class.getName()) != null) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}

jso/impl/src/main/java/org/teavm/jso/impl/JSMethods.java

@@ -131,6 +131,8 @@ final class JSMethods {
             JSObject.class, boolean.class);
     public static final MethodReference THROW_CCE_IF_FALSE = new MethodReference(JS.class, "throwCCEIfFalse",
             boolean.class, JSObject.class, JSObject.class);
+    public static final MethodReference ARGUMENTS_BEGINNING_AT = new MethodReference(JS.class,
+            "argumentsBeginningAt", int.class, JSObject.class);
 
     public static final ValueType JS_OBJECT = ValueType.object(JSObject.class.getName());
     public static final ValueType OBJECT = ValueType.object("java.lang.Object");

jso/impl/src/main/java/org/teavm/jso/impl/JSNativeInjector.java

@@ -237,6 +237,12 @@ public class JSNativeInjector implements Injector, DependencyPlugin {
                 writer.append(")");
                 break;
             }
+            case "argumentsBeginningAt": {
+                writer.appendFunction("$rt_skip").append("(arguments,").ws();
+                context.writeExpr(context.getArgument(0), Precedence.min());
+                writer.append(")");
+                break;
+            }
 
             default:
                 if (methodRef.getName().startsWith("unwrap")) {

jso/impl/src/main/java/org/teavm/jso/impl/JSOPlugin.java

@@ -48,6 +48,7 @@ public class JSOPlugin implements TeaVMPlugin {
         jsHost.addInjectorProvider(new GeneratorAnnotationInstaller<>(new JSBodyGenerator(),
                 DynamicInjector.class.getName()));
         jsHost.addVirtualMethods(aliasRenderer);
+        jsHost.addForcedFunctionMethods(new JSExportedMethodAsFunction());
 
         JSExceptionsGenerator exceptionsGenerator = new JSExceptionsGenerator();
         jsHost.add(new MethodReference(JSExceptions.class, "getJavaException", JSObject.class, Throwable.class),

jso/impl/src/main/java/org/teavm/jso/impl/JSObjectClassTransformer.java

@@ -49,6 +49,7 @@ import org.teavm.model.Program;
 import org.teavm.model.ValueType;
 import org.teavm.model.Variable;
 import org.teavm.model.instructions.ExitInstruction;
+import org.teavm.model.instructions.IntegerConstantInstruction;
 import org.teavm.model.instructions.InvocationType;
 import org.teavm.model.instructions.InvokeInstruction;
 
@@ -111,13 +112,18 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
     private void exposeMethods(ClassHolder classHolder, ExposedClass classToExpose, Diagnostics diagnostics,
             MethodReference functorMethod) {
         int index = 0;
-        for (MethodDescriptor method : classToExpose.methods.keySet()) {
+        for (var entry : classToExpose.methods.entrySet()) {
+            var method = entry.getKey();
+            var export = entry.getValue();
             MethodReference methodRef = new MethodReference(classHolder.getName(), method);
             CallLocation callLocation = new CallLocation(methodRef);
 
-            ValueType[] exportedMethodSignature = Arrays.stream(method.getSignature())
+            var paramCount = method.parameterCount();
-                    .map(type -> ValueType.object(JSObject.class.getName()))
+            if (export.vararg) {
-                    .toArray(ValueType[]::new);
+                --paramCount;
+            }
+            var exportedMethodSignature = new ValueType[paramCount + 1];
+            Arrays.fill(exportedMethodSignature, JSMethods.JS_OBJECT);
             MethodDescriptor exportedMethodDesc = new MethodDescriptor(method.getName() + "$exported$" + index++,
                     exportedMethodSignature);
             MethodHolder exportedMethod = new MethodHolder(exportedMethodDesc);
@@ -134,10 +140,15 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
             for (int i = 0; i < method.parameterCount(); ++i) {
                 variablesToPass[i] = program.createVariable();
             }
+            if (export.vararg) {
+                transformVarargParam(variablesToPass, program, marshallInstructions, exportedMethod, 1);
+            }
 
             for (int i = 0; i < method.parameterCount(); ++i) {
+                var byRef = i == method.parameterCount() - 1 && export.vararg
+                        && typeHelper.isSupportedByRefType(method.parameterType(i));
                 variablesToPass[i] = marshaller.unwrapReturnValue(callLocation, variablesToPass[i],
-                        method.parameterType(i), false, true);
+                        method.parameterType(i), byRef, true);
             }
 
             basicBlock.addAll(marshallInstructions);
@@ -161,8 +172,6 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
             basicBlock.add(exit);
 
             classHolder.addMethod(exportedMethod);
-
-            var export = classToExpose.methods.get(method);
             exportedMethod.getAnnotations().add(createExportAnnotation(export));
 
             if (methodRef.equals(functorMethod)) {
@@ -179,10 +188,14 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
                 continue;
             }
 
+            var paramCount = method.parameterCount();
+            var vararg = method.hasModifier(ElementModifier.VARARGS);
+            if (vararg) {
+                --paramCount;
+            }
             var callLocation = new CallLocation(method.getReference());
-            var exportedMethodSignature = Arrays.stream(method.getSignature())
+            var exportedMethodSignature = new ValueType[paramCount + 1];
-                    .map(type -> ValueType.object(JSObject.class.getName()))
+            Arrays.fill(exportedMethodSignature, JSMethods.JS_OBJECT);
-                    .toArray(ValueType[]::new);
             var exportedMethodDesc = new MethodDescriptor(method.getName() + "$exported$" + index++,
                     exportedMethodSignature);
             var exportedMethod = new MethodHolder(exportedMethodDesc);
@@ -200,10 +213,15 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
             for (int i = 0; i < method.parameterCount(); ++i) {
                 variablesToPass[i] = program.createVariable();
             }
+            if (vararg) {
+                transformVarargParam(variablesToPass, program, marshallInstructions, exportedMethod, 0);
+            }
 
             for (int i = 0; i < method.parameterCount(); ++i) {
+                var byRef = i == method.parameterCount() - 1 && vararg
+                        && typeHelper.isSupportedByRefType(method.parameterType(i));
                 variablesToPass[i] = marshaller.unwrapReturnValue(callLocation, variablesToPass[i],
-                        method.parameterType(i), false, true);
+                        method.parameterType(i), byRef, true);
             }
 
             basicBlock.addAll(marshallInstructions);
@@ -232,6 +250,25 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
         }
     }
 
+    private void transformVarargParam(Variable[] variablesToPass, Program program,
+            List<Instruction> instructions, MethodHolder method, int additionalSkip) {
+        var last = variablesToPass.length - 1;
+
+        var lastConstant = new IntegerConstantInstruction();
+        lastConstant.setReceiver(program.createVariable());
+        lastConstant.setConstant(last + additionalSkip);
+        instructions.add(lastConstant);
+
+        var extractVarargs = new InvokeInstruction();
+        extractVarargs.setType(InvocationType.SPECIAL);
+        extractVarargs.setMethod(JSMethods.ARGUMENTS_BEGINNING_AT);
+        extractVarargs.setArguments(lastConstant.getReceiver());
+        extractVarargs.setReceiver(variablesToPass[last]);
+        instructions.add(extractVarargs);
+
+        method.getAnnotations().add(new AnnotationHolder(JSVararg.class.getName()));
+    }
+
     private AnnotationHolder createExportAnnotation(MethodExport export) {
         String annotationName;
         switch (export.kind) {
@@ -403,7 +440,7 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
                 name = method.getName();
             }
         }
-        return new MethodExport(name, kind);
+        return new MethodExport(name, kind, method.hasModifier(ElementModifier.VARARGS));
     }
 
     private void addFunctorField(ClassHolder cls, MethodReference method) {
@@ -437,10 +474,12 @@ class JSObjectClassTransformer implements ClassHolderTransformer {
     static class MethodExport {
         final String alias;
         final MethodKind kind;
+        boolean vararg;
 
-        MethodExport(String alias, MethodKind kind) {
+        MethodExport(String alias, MethodKind kind, boolean vararg) {
             this.alias = alias;
             this.kind = kind;
+            this.vararg = vararg;
         }
     }
 }

jso/impl/src/main/java/org/teavm/jso/impl/JSTypeHelper.java

@@ -121,8 +121,6 @@ class JSTypeHelper {
                 default:
                     return false;
             }
-        } else if (itemType instanceof ValueType.Object) {
-            return isJavaScriptClass(((ValueType.Object) itemType).getClassName());
         } else {
             return false;
         }

jso/impl/src/main/java/org/teavm/jso/impl/JSVararg.java

@@ -0,0 +1,26 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.jso.impl;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.CLASS)
+@Target(ElementType.METHOD)
+@interface JSVararg {
+}

platform/src/main/java/org/teavm/platform/plugin/AsyncMethodGenerator.java

@@ -18,8 +18,8 @@ package org.teavm.platform.plugin;
 import org.teavm.backend.javascript.codegen.SourceWriter;
 import org.teavm.backend.javascript.spi.Generator;
 import org.teavm.backend.javascript.spi.GeneratorContext;
-import org.teavm.backend.javascript.spi.VirtualMethodContributor;
+import org.teavm.backend.javascript.spi.MethodContributor;
-import org.teavm.backend.javascript.spi.VirtualMethodContributorContext;
+import org.teavm.backend.javascript.spi.MethodContributorContext;
 import org.teavm.backend.javascript.templating.JavaScriptTemplate;
 import org.teavm.backend.javascript.templating.JavaScriptTemplateFactory;
 import org.teavm.dependency.DependencyAgent;
@@ -34,7 +34,7 @@ import org.teavm.model.MethodReader;
 import org.teavm.model.MethodReference;
 import org.teavm.model.ValueType;
 
-public class AsyncMethodGenerator implements Generator, DependencyPlugin, VirtualMethodContributor {
+public class AsyncMethodGenerator implements Generator, DependencyPlugin, MethodContributor {
     private static final MethodDescriptor completeMethod = new MethodDescriptor("complete", Object.class, void.class);
     private static final MethodDescriptor errorMethod = new MethodDescriptor("error", Throwable.class, void.class);
     private JavaScriptTemplate template;
@@ -101,7 +101,7 @@ public class AsyncMethodGenerator implements Generator, DependencyPlugin, Virtua
     }
 
     @Override
-    public boolean isVirtual(VirtualMethodContributorContext context, MethodReference methodRef) {
+    public boolean isContributing(MethodContributorContext context, MethodReference methodRef) {
         ClassReader cls = context.getClassSource().get(methodRef.getClassName());
         if (cls == null) {
             return false;

tests/src/test/java/org/teavm/jso/export/ExportTest.java

@@ -82,6 +82,11 @@ public class ExportTest {
         testExport("exportClasses", ModuleWithExportedClasses.class);
     }
 
+    @Test
+    public void varargs() {
+        testExport("varargs", ModuleWithVararg.class);
+    }
+
     private void testExport(String name, Class<?> moduleClass) {
         if (!Boolean.parseBoolean(System.getProperty("teavm.junit.js", "true"))) {
             return;
@@ -89,6 +94,7 @@ public class ExportTest {
         try {
             var jsTarget = new JavaScriptTarget();
             jsTarget.setModuleType(JSModuleType.ES2015);
+            jsTarget.setObfuscated(false);
             var teavm = new TeaVMBuilder(jsTarget).build();
             var outputDir = new File(targetFile, name);
             teavm.installPlugins();

tests/src/test/java/org/teavm/jso/export/ModuleWithVararg.java

@@ -0,0 +1,90 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.jso.export;
+
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+import org.teavm.jso.JSExport;
+import org.teavm.jso.JSExportClasses;
+import org.teavm.jso.JSObject;
+import org.teavm.jso.JSProperty;
+import org.testng.util.Strings;
+
+@JSExportClasses(ModuleWithVararg.A.class)
+public class ModuleWithVararg {
+    private ModuleWithVararg() {
+    }
+
+    @JSExport
+    public static String strings(String... values) {
+        var sb = new StringBuilder();
+        sb.append("strings: ");
+        sb.append(Strings.join(", ", values));
+        return sb.toString();
+    }
+
+    @JSExport
+    public static String prefixStrings(int a, String... values) {
+        var sb = new StringBuilder();
+        sb.append("strings(").append(a).append("): ");
+        sb.append(Strings.join(", ", values));
+        return sb.toString();
+    }
+
+    @JSExport
+    public static String ints(int... values) {
+        var sb = new StringBuilder();
+        sb.append("ints: ");
+        sb.append(IntStream.of(values).mapToObj(Integer::toString).collect(Collectors.joining(", ")));
+        return sb.toString();
+    }
+
+    @JSExport
+    public static String prefixInts(String prefix, int... values) {
+        var sb = new StringBuilder();
+        sb.append("ints(").append(prefix).append("): ");
+        sb.append(IntStream.of(values).mapToObj(Integer::toString).collect(Collectors.joining(", ")));
+        return sb.toString();
+    }
+
+    @JSExport
+    public static String objects(ObjectWithString... values) {
+        var sb = new StringBuilder();
+        sb.append("objects: ");
+        sb.append(Stream.of(values).map(v -> v.getStringValue()).collect(Collectors.joining(", ")));
+        return sb.toString();
+    }
+
+    public interface ObjectWithString extends JSObject {
+        @JSProperty
+        String getStringValue();
+    }
+
+    public static class A {
+        @JSExport
+        public A() {
+        }
+
+        @JSExport
+        public String strings(String... values) {
+            var sb = new StringBuilder();
+            sb.append("A.strings: ");
+            sb.append(Strings.join(", ", values));
+            return sb.toString();
+        }
+    }
+}

tests/src/test/resources/org/teavm/jso/export/varargs.js

@@ -0,0 +1,28 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+import * as varargs from '/tests/varargs/test.js';
+
+export async function test() {
+    assertEquals("strings: a, b", varargs.strings("a", "b"));
+    assertEquals("strings(23): a, b", varargs.prefixStrings(23, "a", "b"));
+    assertEquals("ints: 23, 42", varargs.ints(23, 42));
+    assertEquals("ints(*): 23, 42", varargs.prefixInts("*", 23, 42));
+    assertEquals("objects: a, b", varargs.objects({ stringValue: "a" }, { stringValue: "b" }));
+
+    let obj = new varargs.A();
+    assertEquals("A.strings: a, b", obj.strings("a", "b"));
+}