826376 - When I accessed firstNewMessage of a nsIMsgFolder object, exception occurred. Why? [Exception... "Component returned failure code: 0x80004003 (NS_ERROR_INVALID_POINTER) [nsIMsgFolder.firstNewMessage]" nsresult: "0x80004003 (NS_ERROR_INVALID_POINTER)"

Status: RESOLVED INVALID

(MailNews Core :: Backend, defect)

Description

[WADA:World Anti-bad-Duping Agency]

When I simply accessed firstNewMessage property of a nsIMsgFolder object, following exception occurred.
Why? Is it design?
How can I avoid such exception when I simply refer the firstNewMessage property of a nsIMsgFolder object, which is actually returned as an property of a nsIMsgFolder object? 

[Exception... "Component returned failure code: 0x80004003 (NS_ERROR_INVALID_POINTER) [nsIMsgFolder.firstNewMessage]"  nsresult: "0x80004003 (NS_ERROR_INVALID_POINTER)"

Note-1:
Exception occurred in both Tb 17.0.1 and Tb truk(Tb 20.0a1 2012/12/18 build).
Note-2:
hasNewMessage==false was returned when I referred the firstNewMessage property of the nsIMsgFolder object from JavaScript code.

Comment 1

[WADA:World Anti-bad-Duping Agency]

Above exception occured in following code for checking property value.
  for(var prop in An_object){ var text = prop + "=" + An_object[prop] ; ... }
This exception can easily be caught by try/catch.
  try      { var text = prop + "=" + An_object[prop] ;  }
  catch(e) { var text = prop + "=" + "(Exception)" + e; }
Because purpose is checking all property's value for trouble shooting, there is no need to use firstNewMessage. So, practically no problem occurs by the exception.

Comment 2

[Hartmut Welpmann [:welpy-cw]]

You have to call hasNewMessages first, see https://searchfox.org/comm-central/rev/72b8ba0761b3881d926be53f77fbf75d5a9316d5/mailnews/base/src/nsMsgDBFolder.cpp#558-561. So this is by design, not a bug.