How to enforce unique error messages

Question

I have been trying to find a way to enforce unique error messages in our application. That is, I want to know exactly which line of code produced the error, so when users contact support we know the source of the error from the message logged.

I found this question which gave me a mechanism (using guids to enforce uniqueness), but one question remains: How do I prevent copy/paste duplication? - specifically, a developer copying the logging line itself:

Log(<guid>, errorMessage);

In this case the guid would be duplicated and no longer useful for identifying the unique line which generated the error.

The one idea I have had which would actually work is writing a tool to be run by our build server which would parse the code for error message guids, keep a list, and fail the build on a duplicate. I'm wondering if there is a cleaner solution.

Other things I've considered:

• There are various ideas using some sort of central listing of error messages, but I have not found one which addresses the copy/paste issue.

• There are also a number of schemes which would require keeping a manual list in some way. I don't want to pursue something like this as it creates the possibility of discrepancies between the list & production code.

• I've also seen suggestions to use the stack trace, but I'm a bit hesitant to do that for security & performance reasons.

Answer 1

I don't know if this is really what you're looking for, but you can include the file, method, line number (and other things) in your log message without needing a unique number that you would later search the source code for if you make use of the System.Diagnostics.StackTrace class. This way, even if there's a copy/paste violation, you still know exactly where the call to Log came from.

Here's a simplified example that returns the file name, method signature, and line number of a stack trace item. Note that this code finds the stack trace item for a call to the "Log" method and returns the next one. That will be more clear shortly:

using System.Diagnostics;  // Needed for the StackTrace class

private static string GetStackTraceInfo()
{
    var stackTrace = new StackTrace(true).GetFrames();

    // Find the item just after the call to teh 'Log' method:
    var item = stackTrace?
        .SkipWhile(st => !st.GetMethod().Name.Equals("Log"))
        .Skip(1)
        .FirstOrDefault();

    return item == null
        ? string.Empty
        : string.Format("{0} => {1}, line #{2}", Path.GetFileName(item.GetFileName()),
            item.GetMethod(), item.GetFileLineNumber());
}

Here's the Log method that enforces the stack trace info added to a log (and this is the method name that we were searching for in the code above):

private static void Log(int id, string message)
{
    Console.WriteLine($"Error #{id}: {message} ({GetStackTraceInfo()})");
}

And an example usage:

private static void Main()
{
    DoSomething();
    DoSomethingElse();

    GetKeyFromUser("\nDone! Press any key to exit...");
}

private static void DoSomething()
{
    Log(1000, "I copied/pasted this error message from somewhere!");
}

private static void DoSomethingElse()
{
    Log(1000, "I copied/pasted this error message from somewhere!");
}

Output