Fix LoggerProviderDebugView.CalculateEnabledLogLevel when the level is None

[joegoldman2]

Fixes #103208.

I didn't find any unit test for this class, I tested the fix manually.

[skyoxZ]

Why logger.Value.MinLevel is null? Maybe there's some deeper problem.

[skyoxZ]

The log level in MessageLogger is nullable and when the filters are applied, the result may be a null level

I'm curious if a null level means None, All, or Undefined. Why it was returning Trace.

[tarekgh]

I don't think this is the right fix.

The fix should change the line 181:

MessageLogger? messageLogger = logger.MessageLoggers?.FirstOrDefault(messageLogger => messageLogger.Logger == loggerInfo.Logger);

To:

            MessageLogger? messageLogger = FirstOrNull(logger.MessageLoggers, loggerInfo.Logger);

            MessageLogger? FirstOrNull(MessageLogger[]? array, ILogger logger)
            {
                if (array is null || array.Length == 0)
                {
                    return null;
                }

                foreach (var item in array)
                {
                    if (item.Logger == logger)
                    {
                        return item;
                    }
                }

                return null;
            }

[tarekgh]

To give some more details, in the failing example, logger.MessageLoggers will be empty array. The line:

MessageLogger? messageLogger = logger.MessageLoggers?.FirstOrDefault(messageLogger => messageLogger.Logger == loggerInfo.Logger);

will return messageLogger equal to the default. MessageLogger is a value type so the returned value will never be null and always has HasValue = true. Then we do new LoggerProviderDebugView(providerName, messageLogger) passing the default value. The LoggerProviderDebugView.CalculateEnabledLogLevel will do the check:

            private static LogLevel? CalculateEnabledLogLevel(MessageLogger? logger)
            {
                if (logger == null)
                {
                    return null;
                }

which will never be true.

[tarekgh]

CC @JamesNK

[joegoldman2]

Thank you @tarekgh. I didn't notice that MessageLogger was a struct, so FirstOrDefault won't return null. I applied and tested your suggestion.

[JamesNK]

You could also do this:

MessageLogger? messageLogger = logger
    .MessageLoggers
    ?.Cast<MessageLogger?>()
    .FirstOrDefault(messageLogger => messageLogger.Logger == loggerInfo.Logger);

But adding the new method is fine. It avoids some struct generics + LINQ.

[tarekgh]

/ba-g the failure is already tracked with the issue dotnet/dnceng#3007.