Nested BeginScope doesn't replace existing keys

[RogueJay]

In version 8, if you nested a BeginScope using the same KeyValue pair, the inner scope would use the newest value.
In version 9, the inner scope value does not replace the existing value.

The following is an XUnit test that works in 8 and fails in 9

		[Fact]
		public void LoggingScope_ReplaceExecutionTagProperty_yWhenCalledTwicetest()
		{
			// Create a context for this specific test to isolate log messages
			using (Serilog.Sinks.TestCorrelator.TestCorrelator.CreateContext())
			using (var logger = new Serilog.LoggerConfiguration().WriteTo.Sink(new TestCorrelatorSink()).Enrich.FromLogContext().CreateLogger())
			{
				Log.Logger = logger;

				var services = new ServiceCollection();
				services.AddLogging(l => l.AddSerilog());

				using var serviceProvider = services.BuildServiceProvider();
				var msLogger = serviceProvider.GetRequiredService<ILogger<Program>>();

				using (msLogger.BeginScope(new Dictionary<string, object> { { ContextProperties.EXECUTION_TAGS, "[TAG1]" } }))
				{
					msLogger.LogInformation("Message1");
					using (msLogger.BeginScope(new Dictionary<string, object> { { ContextProperties.EXECUTION_TAGS, "[TAG2]" } }))
					{
						msLogger.LogInformation("Message2");
					}
				}

				var logEvent = GetLogEvent("Message1");
				Assert.NotNull(logEvent);
				ValidateProperty(logEvent, ContextProperties.EXECUTION_TAGS, "[TAG1]");

				logEvent = GetLogEvent("Message2");
				Assert.NotNull(logEvent);
				ValidateProperty(logEvent, ContextProperties.EXECUTION_TAGS, "[TAG2]");   <-- FAILS BECAUSE TAG1 IS STILL USED
			}
		}

		private static LogEvent? GetLogEvent(string message)
			=> TestCorrelator.GetLogEventsFromCurrentContext().FirstOrDefault(e => e.MessageTemplate.Text == message);

		private static void ValidateProperty(LogEvent logEvent, string name, string value)
		{
			Assert.Contains(name, logEvent.Properties.Keys);
			Assert.True(logEvent.Properties.TryGetValue(name, out LogEventPropertyValue? result));
			Assert.Equal(value, result.ToString().Replace("\"", ""));
		}

I don't know if this is related, but looking at the stack at the point Message2 is about to be logged, I see the following. For version 8.0, the Scopes variable is null

[nblumhardt]

Thanks for the report! Looks like a good find 👍