[JSC] WebAssembly.Exception: the traceStack stack is the stack of an Error created there

JSTests/wasm/stress/exception-trace-stack-is-error-stack.js

@@ -0,0 +1,21 @@
+import * as assert from "../assert.js";
+
+const tag = new WebAssembly.Tag({ parameters: ["i32"] });
+
+function makeBoth() {
+    return [new WebAssembly.Exception(tag, [0], { traceStack: true }), new Error()];
+}
+
+// Both are created on one line, so only the column of the first frame differs.
+const withoutFirstColumn = stack => stack.replace(/:\d+$/m, "");
+
+const [exception, error] = makeBoth();
+assert.eq(typeof exception.stack, "string");
+assert.eq(withoutFirstColumn(exception.stack), withoutFirstColumn(error.stack));
+assert.eq(Object.hasOwn(exception, "stack"), false);
+
+// With no frames an Error has no stack. Interpreter::stackTraceAsString gave "" here.
+Error.stackTraceLimit = 0;
+const [exceptionWithoutFrames, errorWithoutFrames] = makeBoth();
+assert.eq(errorWithoutFrames.stack, undefined);
+assert.eq(exceptionWithoutFrames.stack, undefined);

Source/JavaScriptCore/wasm/js/WebAssemblyExceptionConstructor.cpp

@@ -29,6 +29,7 @@
 #if ENABLE(WEBASSEMBLY)
 
 #include "BuiltinNames.h"
+#include "ErrorInstanceInlines.h"
 #include "Interpreter.h"
 #include "IteratorOperations.h"
 #include "JITOpaqueByproducts.h"
@@ -100,10 +101,20 @@ JSC_DEFINE_HOST_FUNCTION(constructJSWebAssemblyException, (JSGlobalObject* globa
 
     auto* exception = JSWebAssemblyException::create(vm, structure, tag->tag(), WTF::move(payload));
     if (traceStack) {
+#if USE(BUN_JSC_ADDITIONS)
+        // Take the stack of an Error created here, so that it goes through VM::onComputeErrorInfoJSValue
+        // like every other stack. Interpreter::stackTraceAsString skips that hook.
+        constexpr bool useCurrentFrame = false;
+        auto* error = ErrorInstance::create(vm, globalObject->errorStructure(), String(), JSValue(), nullptr, TypeNothing, ErrorType::Error, useCurrentFrame);
+        JSValue stack = error->get(globalObject, vm.propertyNames->stack);
+        RETURN_IF_EXCEPTION(scope, { });
+        exception->putDirect(vm, vm.propertyNames->builtinNames().stackPrivateName(), stack, static_cast<unsigned>(PropertyAttribute::DontEnum | PropertyAttribute::ReadOnly | PropertyAttribute::DontDelete));
+#else
         Vector<StackFrame> stackTrace;
         constexpr size_t framesToSkip = 1;
         vm.interpreter.getStackTrace(exception, stackTrace, framesToSkip, globalObject->stackTraceLimit().value_or(0));
         exception->putDirect(vm, vm.propertyNames->builtinNames().stackPrivateName(), jsString(vm, Interpreter::stackTraceAsString(vm, stackTrace)), static_cast<unsigned>(PropertyAttribute::DontEnum | PropertyAttribute::ReadOnly | PropertyAttribute::DontDelete));
+#endif
     }
 
     return JSValue::encode(exception);