perf(logs): avoid string allocation when no parameters are passed to be formatted via the template

Author: Flash0ver

src/Sentry/Internal/DefaultSentryStructuredLogger.cs

@@ -29,15 +29,18 @@ private protected override void CaptureLog(SentryLogLevel level, string template
         var timestamp = _clock.GetUtcNow();
         SentryLog.GetTraceIdAndSpanId(_hub, out var traceId, out var spanId);
 
-        string message;
-        try
-        {
-            message = string.Format(CultureInfo.InvariantCulture, template, parameters ?? []);
-        }
-        catch (FormatException e)
+        string message = template;
+        if (parameters is { Length: > 0 })
         {
-            _options.DiagnosticLogger?.LogError(e, "Template string does not match the provided argument. The Log will be dropped.");
-            return;
+            try
+            {
+                message = string.Format(CultureInfo.InvariantCulture, template, parameters);
+            }
+            catch (FormatException e)
+            {
+                _options.DiagnosticLogger?.LogError(e, "Template string does not match the provided argument. The Log will be dropped.");
+                return;
+            }
         }
 
         ImmutableArray<KeyValuePair<string, object>> @params = default;

test/Sentry.Tests/SentryStructuredLoggerTests.Format.cs

@@ -83,6 +83,33 @@ public void Log_ConfigureLog_Disabled_DoesNotCaptureEnvelope(SentryLogLevel leve
 
         _fixture.Hub.Received(0).CaptureEnvelope(Arg.Any<Envelope>());
     }
+
+    [Theory]
+    [InlineData(SentryLogLevel.Trace)]
+    [InlineData(SentryLogLevel.Debug)]
+    [InlineData(SentryLogLevel.Info)]
+    [InlineData(SentryLogLevel.Warning)]
+    [InlineData(SentryLogLevel.Error)]
+    [InlineData(SentryLogLevel.Fatal)]
+    public void Log_WithoutParameters_DoesNotAttachTemplateAttribute(SentryLogLevel level)
+    {
+        _fixture.Options.Experimental.EnableLogs = true;
+        var logger = _fixture.GetSut();
+
+        Envelope envelope = null!;
+        _fixture.Hub.CaptureEnvelope(Arg.Do<Envelope>(arg => envelope = arg));
+
+        logger.Log(level, "Message Text");
+        logger.Flush();
+
+        _fixture.Hub.Received(1).CaptureEnvelope(Arg.Any<Envelope>());
+        var log = envelope.ShouldContainSingleLog();
+
+        log.Level.Should().Be(level);
+        log.Message.Should().Be("Message Text");
+        log.Template.Should().BeNull();
+        log.Parameters.Should().BeEmpty();
+    }
 }
 
 file static class SentryStructuredLoggerExtensions

test/Sentry.Tests/SentryStructuredLoggerTests.cs

@@ -301,4 +301,14 @@ public static void AssertLog(this SentryStructuredLoggerTests.Fixture fixture, S
     {
         return new KeyValuePair<string, object?>(name, value);
     }
+
+    public static SentryLog ShouldContainSingleLog(this Envelope envelope)
+    {
+        var envelopeItem = envelope.Items.Should().ContainSingle().Which;
+        var serializable = envelopeItem.Payload.Should().BeOfType<JsonSerializable>().Which;
+        var log = serializable.Source.Should().BeOfType<StructuredLog>().Which;
+
+        log.Items.Length.Should().Be(1);
+        return log.Items[0];
+    }
 }