-- Allow the DOM script object factory to turn XPConnect return values into proper nsIException objects.

-- Make nsDOMClassInfo::ThrowJSException never throw null as an exception.
-- Make XPCException::ToString grab the description of the result as well as the name.

r+sr=jst

dom/src/base/nsDOMClassInfo.cpp

@@ -1433,25 +1433,46 @@ nsDOMClassInfo::WrapNative(JSContext *cx, JSObject *scope, nsISupports *native,
 nsresult
 nsDOMClassInfo::ThrowJSException(JSContext *cx, nsresult aResult)
 {
-  nsCOMPtr<nsIExceptionService> xs =
-    do_GetService(NS_EXCEPTIONSERVICE_CONTRACTID);
-  if (!xs)
-    return NS_ERROR_FAILURE;
+  do {
+    nsCOMPtr<nsIExceptionService> xs =
+      do_GetService(NS_EXCEPTIONSERVICE_CONTRACTID);
+    if (!xs) {
+      break;
+    }
 
-  nsCOMPtr<nsIExceptionManager> xm;
-  nsresult rv = xs->GetCurrentExceptionManager(getter_AddRefs(xm));
-  NS_ENSURE_SUCCESS(rv, rv);
+    nsCOMPtr<nsIExceptionManager> xm;
+    nsresult rv = xs->GetCurrentExceptionManager(getter_AddRefs(xm));
+    if (NS_FAILED(rv)) {
+      break;
+    }
 
-  nsCOMPtr<nsIException> exception;
-  rv = xm->GetExceptionFromProvider(aResult, 0, getter_AddRefs(exception));
+    nsCOMPtr<nsIException> exception;
+    rv = xm->GetExceptionFromProvider(aResult, 0, getter_AddRefs(exception));
+    if (NS_FAILED(rv) || !exception) {
+      break;
+    }
 
-  jsval jv;
-  nsCOMPtr<nsIXPConnectJSObjectHolder> holder;
-  rv = WrapNative(cx, ::JS_GetGlobalObject(cx), exception,
-                  NS_GET_IID(nsIException), &jv, getter_AddRefs(holder));
-  NS_ENSURE_SUCCESS(rv, rv);
-  JS_SetPendingException(cx, jv);
+    jsval jv;
+    nsCOMPtr<nsIXPConnectJSObjectHolder> holder;
+    rv = WrapNative(cx, ::JS_GetGlobalObject(cx), exception,
+                    NS_GET_IID(nsIException), &jv, getter_AddRefs(holder));
+    if (NS_FAILED(rv) || JSVAL_IS_NULL(jv)) {
+      break;
+    }
+    JS_SetPendingException(cx, jv);
 
+    return NS_OK;
+  } while (0);
+
+  // XXX This probably wants to be localized, but that can fail in ways that
+  // are hard to report correctly.
+  JSString *str =
+    JS_NewStringCopyZ(cx, "An error occured throwing an exception");
+  if (!str) {
+    // JS_NewStringCopyZ reported the error for us.
+    return NS_OK; 
+  }
+  JS_SetPendingException(cx, STRING_TO_JSVAL(str));
   return NS_OK;
 }
 

dom/src/base/nsDOMScriptObjectFactory.cpp

@@ -1,4 +1,5 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=2 sw=2 et tw=78:
  *
  * ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
@@ -51,6 +52,7 @@
  */
 
 #include "nsDOMScriptObjectFactory.h"
+#include "xpcexception.h"
 #include "nsScriptNameSpaceManager.h"
 #include "nsIObserverService.h"
 #include "nsJSEnvironment.h"
@@ -82,6 +84,7 @@ nsDOMScriptObjectFactory::nsDOMScriptObjectFactory()
     xs->RegisterExceptionProvider(this, NS_ERROR_MODULE_SVG);
 #endif
     xs->RegisterExceptionProvider(this, NS_ERROR_MODULE_DOM_XPATH);
+    xs->RegisterExceptionProvider(this, NS_ERROR_MODULE_XPCONNECT);
   }
 }
 
@@ -193,12 +196,29 @@ nsDOMScriptObjectFactory::Observe(nsISupports *aSubject,
       xs->UnregisterExceptionProvider(this, NS_ERROR_MODULE_SVG);
 #endif
       xs->UnregisterExceptionProvider(this, NS_ERROR_MODULE_DOM_XPATH);
+      xs->UnregisterExceptionProvider(this, NS_ERROR_MODULE_XPCONNECT);
     }
   }
 
   return NS_OK;
 }
 
+static nsresult
+CreateXPConnectException(nsresult aResult, nsIException *aDefaultException,
+                         nsIException **_retval)
+{
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIXPCException> exception(
+      do_CreateInstance("@mozilla.org/js/xpc/Exception;1", &rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = exception->Initialize(nsnull, aResult, nsnull, nsnull, nsnull, nsnull);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  NS_ADDREF(*_retval = exception);
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDOMScriptObjectFactory::GetException(nsresult result,
 				       nsIException *aDefaultException,
@@ -214,6 +234,8 @@ nsDOMScriptObjectFactory::GetException(nsresult result,
 #endif
     case NS_ERROR_MODULE_DOM_XPATH:
       return NS_NewXPathException(result, aDefaultException, _retval);
+    case NS_ERROR_MODULE_XPCONNECT:
+      return CreateXPConnectException(result, aDefaultException, _retval);
     default:
       return NS_NewDOMException(result, aDefaultException, _retval);
   }

js/src/xpconnect/src/xpcexception.cpp

@@ -367,12 +367,17 @@ nsXPCException::ToString(char **_retval)
             return rv;
     }
 
-    const char* msg = mMessage ? mMessage : defaultMsg;
+    const char* msg = mMessage ? mMessage : nsnull;
     const char* location = indicatedLocation ?
                                 indicatedLocation : defaultLocation;
     const char* resultName = mName;
-    if(!resultName && !NameAndFormatForNSResult(mResult, &resultName, nsnull))
+    if(!resultName && !NameAndFormatForNSResult(mResult, &resultName,
+                                                (!msg) ? &msg : nsnull))
+    {
+        if(!msg)
+            msg = defaultMsg;
         resultName = "<unknown>";
+    }
     const char* data = mData ? "yes" : "no";
 
     char* temp = JS_smprintf(format, msg, mResult, resultName, location, data);