parameterize original log event

Author: KodrAus

src/SeqCli/Ingestion/JsonLogEventReader.cs

@@ -77,7 +77,7 @@ public static LogEvent ReadFromJObject(JObject jObject)
             if (serilogLevel != LogEventLevel.Information)
                 jObject.Add("@l", new JValue(serilogLevel.ToString()));
 
-            jObject.Add("SeqCliOriginalLevel", originalLevel);
+            jObject.Add(LevelMapping.SurrogateLevelProperty, originalLevel);
         }
 
         return LogEventReader.ReadFromJObject(jObject);

src/SeqCli/Levels/LevelMapping.cs

@@ -20,6 +20,9 @@ namespace SeqCli.Levels;
 
 public static class LevelMapping
 {
+    // Use a "hygienic" name for the original level value to avoid collisions
+    internal static readonly string SurrogateLevelProperty = $"_SeqcliOriginalLevel_{Guid.NewGuid():N}";
+
     static readonly Dictionary<string, (string, LogEventLevel)> LevelsByName =
         new(StringComparer.OrdinalIgnoreCase)
         {

src/SeqCli/Output/OutputFormatter.cs

@@ -1,3 +1,4 @@
+using SeqCli.Levels;
 using Serilog.Formatting;
 using Serilog.Templates;
 
@@ -6,6 +7,6 @@ namespace SeqCli.Output;
 static class OutputFormatter
 {
     internal static readonly ITextFormatter Json = new ExpressionTemplate(
-        "{ {@t, @mt, @l: coalesce(SeqCliOriginalLevel, if @l = 'Information' then undefined() else @l), @x, @sp, @tr, @ps, @st, ..rest()} }\n"
+        $"{{ {{@t, @mt, @l: coalesce({LevelMapping.SurrogateLevelProperty}, if @l = 'Information' then undefined() else @l), @x, @sp, @tr, @ps, @st, ..rest()}} }}\n"
     );
 }

src/SeqCli/PlainText/LogEvents/LogEventBuilder.cs

@@ -38,7 +38,7 @@ public static LogEvent FromProperties(IDictionary<string, object?> properties, s
         var props = GetLogEventProperties(properties, remainder, level);
 
         var fallbackMappedLevel = level != null ? LevelMapping.ToSerilogLevel(level) : LogEventLevel.Information;
-        properties["SeqCliOriginalLevel"] = level;
+        properties[LevelMapping.SurrogateLevelProperty] = level;
 
         return new LogEvent(
             timestamp,

test/SeqCli.EndToEnd/Ingest/LevelledTextIngestionTestCase.cs

@@ -27,5 +27,7 @@ public async Task ExecuteAsync(
         // Since @l is a token, no level mapping is applied
         Assert.Equal(1, events.Count(e => e.Level == "INFO"));
         Assert.Equal(1, events.Count(e => e.Level == "WARN"));
+        
+        Assert.DoesNotContain(events, e => e.Properties.Any(p => p.Name.StartsWith("_Seqcli")));
     }
 }