Bug 1650776 - Introduce Debugger.Object.isError to check for error objects. r=tcampbell

Differential Revision: https://phabricator.services.mozilla.com/D82454

js/src/debugger/Object.cpp

@@ -171,6 +171,7 @@ struct MOZ_STACK_CLASS DebuggerObject::CallData {
   bool boundThisGetter();
   bool boundArgumentsGetter();
   bool allocationSiteGetter();
+  bool isErrorGetter();
   bool errorMessageNameGetter();
   bool errorNotesGetter();
   bool errorLineNumberGetter();
@@ -517,6 +518,11 @@ bool DebuggerObject::CallData::errorMessageNameGetter() {
   return true;
 }
 
+bool DebuggerObject::CallData::isErrorGetter() {
+  args.rval().setBoolean(object->isError());
+  return true;
+}
+
 bool DebuggerObject::CallData::errorNotesGetter() {
   return DebuggerObject::getErrorNotes(cx, object, args.rval());
 }
@@ -1538,6 +1544,7 @@ const JSPropertySpec DebuggerObject::properties_[] = {
     JS_DEBUG_PSG("boundThis", boundThisGetter),
     JS_DEBUG_PSG("boundArguments", boundArgumentsGetter),
     JS_DEBUG_PSG("allocationSite", allocationSiteGetter),
+    JS_DEBUG_PSG("isError", isErrorGetter),
     JS_DEBUG_PSG("errorMessageName", errorMessageNameGetter),
     JS_DEBUG_PSG("errorNotes", errorNotesGetter),
     JS_DEBUG_PSG("errorLineNumber", errorLineNumberGetter),
@@ -1682,7 +1689,7 @@ bool DebuggerObject::isPromise() const {
   JSObject* referent = this->referent();
 
   if (IsCrossCompartmentWrapper(referent)) {
-    /* We only care about promises, so CheckedUnwrapStatic is OK. */
+    // We only care about promises, so CheckedUnwrapStatic is OK.
     referent = CheckedUnwrapStatic(referent);
     if (!referent) {
       return false;
@@ -1692,6 +1699,20 @@ bool DebuggerObject::isPromise() const {
   return referent->is<PromiseObject>();
 }
 
+bool DebuggerObject::isError() const {
+  JSObject* referent = this->referent();
+
+  if (IsCrossCompartmentWrapper(referent)) {
+    // We only check for error classes, so CheckedUnwrapStatic is OK.
+    referent = CheckedUnwrapStatic(referent);
+    if (!referent) {
+      return false;
+    }
+  }
+
+  return referent->is<ErrorObject>();
+}
+
 /* static */
 bool DebuggerObject::getClassName(JSContext* cx, HandleDebuggerObject object,
                                   MutableHandleString result) {

js/src/debugger/Object.h

@@ -169,6 +169,7 @@ class DebuggerObject : public NativeObject {
   bool isGlobal() const;
   bool isScriptedProxy() const;
   bool isPromise() const;
+  bool isError() const;
   JSAtom* name(JSContext* cx) const;
   JSAtom* displayName(JSContext* cx) const;
   JS::PromiseState promiseState() const;

js/src/doc/Debugger/Debugger.Object.md

@@ -154,6 +154,9 @@ If the referent is a function that is debuggee code, a
 environment enclosing the function when it was created. If the referent
 is a function proxy or not debuggee code, this is `undefined`.
 
+### `isError`
+`true` if the referent is any potentially wrapped Error; `false` otherwise.
+
 ### `errorMessageName`
 If the referent is an error created with an engine internal message template
 this is a string which is the name of the template; `undefined` otherwise.

js/src/jit-test/tests/debug/isError.js

@@ -0,0 +1,19 @@
+let g = newGlobal({newCompartment: true});
+let dbg = new Debugger();
+let gw = dbg.addDebuggee(g);
+
+g.error1 = new Error()
+g.error2 = new g.Error()
+g.error3 = new g.TypeError();
+
+let error1DO = gw.getOwnPropertyDescriptor('error1').value;
+let error2DO = gw.getOwnPropertyDescriptor('error2').value;
+let error3DO = gw.getOwnPropertyDescriptor('error3').value;
+
+assertEq(error1DO.isError, true);
+assertEq(error2DO.isError, true);
+assertEq(error3DO.isError, true);
+
+g.nonError = new Array();
+let nonErrorDO = gw.getOwnPropertyDescriptor('nonError').value;
+assertEq(nonErrorDO.isError, false);