wasm gc: fix issue with JS exceptions, trying to propagate Java exception message to JS error message

core/src/main/java/org/teavm/backend/wasm/WasmGCTarget.java

@@ -221,6 +221,12 @@ public class WasmGCTarget implements TeaVMTarget, TeaVMWasmGCHost {
             removeStringEntryFunction.setExportName("reportGarbageCollectedString");
         }
 
+        var exceptionMessageRef = new MethodReference(Throwable.class, "getMessage", Throwable.class);
+        if (controller.getDependencyInfo().getMethod(exceptionMessageRef) != null) {
+            var exceptionMessageFunction = declarationsGenerator.functions().forInstanceMethod(exceptionMessageRef);
+            exceptionMessageFunction.setExportName("exceptionMessage");
+        }
+
         moduleGenerator.generate();
         customGenerators.contributeToModule(module);
         adjustModuleMemory(module);

core/src/main/java/org/teavm/backend/wasm/gc/WasmGCDependencies.java

@@ -19,6 +19,8 @@ import java.util.Arrays;
 import java.util.List;
 import org.teavm.backend.wasm.WasmRuntime;
 import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
+import org.teavm.dependency.AbstractDependencyListener;
+import org.teavm.dependency.DependencyAgent;
 import org.teavm.dependency.DependencyAnalyzer;
 import org.teavm.model.MethodReference;
 
@@ -105,6 +107,17 @@ public class WasmGCDependencies {
         analyzer.linkMethod(new MethodReference(WasmGCSupport.class, "throwCloneNotSupportedException",
                 void.class)).use();
         analyzer.linkMethod(new MethodReference(NullPointerException.class, "<init>", void.class)).use();
+
+        analyzer.addDependencyListener(new AbstractDependencyListener() {
+            @Override
+            public void classReached(DependencyAgent agent, String className) {
+                if (className.equals(Throwable.class.getName())) {
+                    agent.linkMethod(new MethodReference(Throwable.class, "getMessage", String.class))
+                            .propagate(0, Throwable.class)
+                            .use();
+                }
+            }
+        });
     }
 
     private void contributeInitializerUtils() {

core/src/main/resources/org/teavm/backend/wasm/wasm-gc-runtime.js

@@ -38,6 +38,24 @@ TeaVM.wasm = function() {
         imports.teavmMath = Math;
     }
 
+    let javaExceptionSymbol = Symbol("javaException");
+    class JavaError extends Error {
+        constructor(javaException) {
+            super();
+            this[javaExceptionSymbol] = javaException;
+        }
+        get message() {
+            let exceptionMessage = exports.exceptionMessage;
+            if (typeof exceptionMessage === "function") {
+                let message = exceptionMessage(this[javaExceptionSymbol]);
+                if (message != null) {
+                    return stringToJava(message);
+                }
+            }
+            return "(could not fetch message)";
+        }
+    }
+
     function dateImports(imports) {
         imports.teavmDate = {
             currentTimeMillis: () => new Date().getTime(),
@@ -119,7 +137,6 @@ TeaVM.wasm = function() {
         let javaObjectSymbol = Symbol("javaObject");
         let functionsSymbol = Symbol("functions");
         let functionOriginSymbol = Symbol("functionOrigin");
-        let javaExceptionSymbol = Symbol("javaException");
 
         let jsWrappers = new WeakMap();
         let javaWrappers = new WeakMap();
@@ -179,9 +196,8 @@ TeaVM.wasm = function() {
                             return wrapper;
                         }
                     }
-                    let wrapper = new Error();
+                    let wrapper = new JavaError(javaException);
                     javaExceptionWrappers.set(javaException, new WeakRef(wrapper));
-                    wrapper[javaExceptionSymbol] = javaException;
                     return wrapper;
                 }
             }

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

@@ -15,5 +15,5 @@
  */
 package org.teavm.jso.impl;
 
-@interface JSBodyDelegate {
+public @interface JSBodyDelegate {
 }

jso/impl/src/main/java/org/teavm/jso/impl/wasmgc/WasmGCJSDependencies.java

@@ -22,6 +22,7 @@ import org.teavm.dependency.DependencyAgent;
 import org.teavm.dependency.MethodDependency;
 import org.teavm.jso.JSObject;
 import org.teavm.jso.impl.JS;
+import org.teavm.jso.impl.JSBodyDelegate;
 import org.teavm.jso.impl.JSWrapper;
 import org.teavm.model.MethodReference;
 
@@ -33,15 +34,30 @@ class WasmGCJSDependencies extends AbstractDependencyListener {
 
     @Override
     public void methodReached(DependencyAgent agent, MethodDependency method) {
-        if (method.getMethod().getOwnerName().equals(JS.class.getName())) {
+        var methodReader = method.getMethod();
-            if (method.getMethod().getName().equals("jsArrayItem")) {
+        if (methodReader.getOwnerName().equals(JS.class.getName())) {
+            switch (methodReader.getName()) {
+                case "jsArrayItem":
                     method.getVariable(1).getArrayItem().connect(method.getResult());
+                    break;
+                case "invoke":
+                case "apply":
+                case "construct":
+                case "get":
+                case "getPure":
+                case "set":
+                case "setPure":
+                case "global":
+                    method.getThrown().propagate(agent.getType(WasmGCExceptionWrapper.class.getName()));
+                    break;
             }
-        } else if (method.getMethod().getOwnerName().equals(JSWrapper.class.getName())) {
+        } else if (methodReader.getOwnerName().equals(JSWrapper.class.getName())) {
-            if (method.getMethod().getName().equals("wrap")) {
+            if (methodReader.getName().equals("wrap")) {
                 agent.linkMethod(new MethodReference(JSWrapper.class, "createWrapper", JSObject.class, Object.class))
                         .use();
             }
+        } else if (methodReader.getAnnotations().get(JSBodyDelegate.class.getName()) != null) {
+            method.getThrown().propagate(agent.getType(WasmGCExceptionWrapper.class.getName()));
         }
     }
 

tests/src/test/java/org/teavm/jso/test/ExceptionsTest.java

@@ -27,7 +27,6 @@ import org.teavm.jso.core.JSError;
 import org.teavm.junit.EachTestCompiledSeparately;
 import org.teavm.junit.OnlyPlatform;
 import org.teavm.junit.SkipJVM;
-import org.teavm.junit.SkipPlatform;
 import org.teavm.junit.TeaVMTestRunner;
 import org.teavm.junit.TestPlatform;
 
@@ -103,7 +102,6 @@ public class ExceptionsTest {
     }
 
     @Test
-    @SkipPlatform(TestPlatform.WEBASSEMBLY_GC)
     public void catchNativeExceptionAsRuntimeException() {
         StringBuilder sb = new StringBuilder();
         try {