Updating error message return from unserializable JavaScript result in IE

In the case where a user JavaScript execution completes successfully, but
the resulting option is not serializable via JSON (because of cyclical
references or similar), the error message that the execution errored due to
the failed serialization was being suppressed.

Author: jimevans

cpp/iedriver/Script.cpp

@@ -573,6 +573,12 @@ int Script::ConvertResultToJsonValue(IElementManager* element_manager,
                                                          this->result_,
                                                          value);
   if (status_code != WD_SUCCESS) {
+    // Attempting to convert the VARIANT script result to a JSON value
+    // has failed. As a last-ditch effort, attempt to use JSON.stringify()
+    // to accomplish the same thing.
+    // TODO: Check the return value for a cyclic reference error first, and
+    // if that's the reason for the failure to convert, we can bypass this
+    // script execution and just return that as the error reason.
     LOG(DEBUG) << "Script result could not be directly converted; "
                << "attempting to use JSON.stringify()";
     std::wstring json_stringify_script = ANONYMOUS_FUNCTION_START;
@@ -600,6 +606,14 @@ int Script::ConvertResultToJsonValue(IElementManager* element_manager,
           *value = interim_value;
         }
       }
+    } else {
+      // If the call to JSON.stringify() fails, log the description of the
+      // error thrown by that call as the reason for the script returning a
+      // JavaScript error.
+      if (stringify_script_wrapper.result().vt == VT_BSTR) {
+        std::wstring error = stringify_script_wrapper.result().bstrVal;
+        *value = StringUtilities::ToString(error);
+      }
     }
   }
   return status_code;