BUG OF THE MONTH | Potential null dereference

V3080 Possible null dereference. Consider inspecting ‘ItemSelectionCondition’. System.Management.Automation displayDescriptionData_List.cs 352

internal bool SafeForExport()
{
  return DisplayEntry.SafeForExport() &&
         ItemSelectionCondition == null 
      || ItemSelectionCondition.SafeForExport();
}

There is a risk of getting a NullReferenceException when executing this code. The ItemSelectionCondition.SafeForExport() subexpression will be evaluated only if the first subexpression evaluates to false. Therefore, if DisplayEntry.SafeForExport() returns false and ItemSelectionCondition == null, the second subexpression, ItemSelectionCondition.SafeForExport(), will be evaluated, and that’s where the null dereference will occur (and raise the exception). Correct variant can be like this:

internal bool SafeForExport()
{
  return (DisplayEntry.SafeForExport() && 
          ItemSelectionCondition == null)
      || (ItemSelectionCondition != null &&
          ItemSelectionCondition.SafeForExport());
}

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