Merge pull request #128 from Distributive-Network/feat/catch-py-exceptions

Handle nested exceptions in different languages

Author: Xmader

src/jsTypeFactory.cc

@@ -196,6 +196,21 @@ JS::Value jsTypeFactorySafe(JSContext *cx, PyObject *object) {
   return v;
 }
 
+void setPyException(JSContext *cx) {
+  // Python `exit` and `sys.exit` only raise a SystemExit exception to end the program
+  // We definitely don't want to catch it in JS
+  if (PyErr_ExceptionMatches(PyExc_SystemExit)) {
+    return;
+  }
+
+  PyObject *type, *value, *traceback;
+  PyErr_Fetch(&type, &value, &traceback); // also clears the error indicator
+
+  JSObject *jsException = ExceptionType(value).toJsError(cx);
+  JS::RootedValue jsExceptionValue(cx, JS::ObjectValue(*jsException));
+  JS_SetPendingException(cx, jsExceptionValue);
+}
+
 bool callPyFunc(JSContext *cx, unsigned int argc, JS::Value *vp) {
   JS::CallArgs callargs = JS::CallArgsFromVp(argc, vp);
 
@@ -213,6 +228,7 @@ bool callPyFunc(JSContext *cx, unsigned int argc, JS::Value *vp) {
     PyObject *pyRval = _PyObject_CallNoArg(pyFunc); // in Python 3.8, the API is only available under the name with a leading underscore
     #endif
     if (PyErr_Occurred()) { // Check if an exception has already been set in Python error stack
+      setPyException(cx);
       return false;
     }
     // @TODO (Caleb Aikens) need to check for python exceptions here
@@ -233,11 +249,13 @@ bool callPyFunc(JSContext *cx, unsigned int argc, JS::Value *vp) {
 
   PyObject *pyRval = PyObject_Call(pyFunc, pyArgs, NULL);
   if (PyErr_Occurred()) {
+    setPyException(cx);
     return false;
   }
   // @TODO (Caleb Aikens) need to check for python exceptions here
   callargs.rval().set(jsTypeFactory(cx, pyRval));
   if (PyErr_Occurred()) {
+    setPyException(cx);
     return false;
   }
 

tests/python/test_pythonmonkey_eval.py

@@ -119,6 +119,30 @@ def test_eval_exceptions():
     with pytest.raises(pm.SpiderMonkeyError, match="Error: Python BaseException: 123"):
         js_rethrow(BaseException("123"))
 
+def test_eval_exceptions_nested_py_js_py():
+    def c():
+        raise Exception('this is an exception')
+    b = pm.eval('''(x) => {
+        try { 
+            x() 
+        } catch(e) {
+            return "Caught in JS " + e;
+        }
+    }''')
+    assert b(c) == "Caught in JS Error: Python Exception: this is an exception"
+
+def test_eval_exceptions_nested_js_py_js():
+    c = pm.eval("() => { throw TypeError('this is an exception'); }")
+
+    def b(x):
+        try:
+            x()
+            return ""
+        except Exception as e:
+            return "Caught in Py " + str(e)
+    ret = b(c)
+    assert ("Caught in Py Error in" in ret) and ("TypeError: this is an exception" in ret)
+
 def test_eval_undefined():
     x = pm.eval("undefined")
     assert x == None