Fix segment handling when formatter retries

Author: xoofx

src/XenoAtom.Logging.Tests/LogFormatterBufferTests.cs

@@ -0,0 +1,109 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// Licensed under the BSD-Clause 2 license.
+// See license.txt file in the project root for full license information.
+
+using XenoAtom.Logging.Helpers;
+
+namespace XenoAtom.Logging.Tests;
+
+[TestClass]
+public class LogFormatterBufferTests
+{
+    [TestInitialize]
+    public void Initialize()
+    {
+        LogManager.Shutdown();
+    }
+
+    [TestCleanup]
+    public void Cleanup()
+    {
+        LogManager.Shutdown();
+    }
+
+    [TestMethod]
+    public void LogFormatterBuffer_ResetsSegmentsBetweenRetries()
+    {
+        var formatter = new FailOnceSegmentingFormatter();
+        var writer = new BufferCaptureWriter(formatter);
+
+        var config = new LogManagerConfig
+        {
+            RootLogger =
+            {
+                MinimumLevel = LogLevel.Trace,
+                Writers =
+                {
+                    writer
+                }
+            }
+        };
+
+        LogManager.Initialize(config);
+        var logger = LogManager.GetLogger("Tests.FormatterBuffer.Retry");
+        logger.Info("hello");
+        LogManager.Shutdown();
+
+        Assert.AreEqual("ok", writer.Text);
+        Assert.AreEqual(1, writer.Segments.Length);
+        Assert.AreEqual(LogMessageFormatSegmentKind.Text, writer.Segments[0].Kind);
+    }
+
+    private sealed class BufferCaptureWriter : LogWriter
+    {
+        private readonly LogFormatter _formatter;
+
+        public BufferCaptureWriter(LogFormatter formatter)
+        {
+            _formatter = formatter;
+        }
+
+        public string? Text { get; private set; }
+
+        public LogMessageFormatSegment[] Segments { get; private set; } = [];
+
+        protected override void Log(LogMessage logMessage)
+        {
+            using var formatterBuffer = new LogFormatterBuffer();
+            var segments = new LogMessageFormatSegments(enabled: true);
+            try
+            {
+                var text = formatterBuffer.Format(logMessage, _formatter, ref segments);
+                Text = text.ToString();
+                Segments = segments.AsSpan().ToArray();
+            }
+            finally
+            {
+                segments.Dispose();
+            }
+        }
+    }
+
+    private sealed record FailOnceSegmentingFormatter : LogFormatter
+    {
+        private int _tryCount;
+
+        public override bool TryFormat(LogMessage logMessage, Span<char> destination, out int charsWritten, ref LogMessageFormatSegments segments)
+        {
+            segments.Add(0, 0, LogMessageFormatSegmentKind.Text);
+
+            if (_tryCount++ == 0)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            if (destination.Length < 2)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            destination[0] = 'o';
+            destination[1] = 'k';
+            charsWritten = 2;
+            return true;
+        }
+    }
+}
+

src/XenoAtom.Logging/Helpers/LogFormatterBuffer.cs

@@ -29,8 +29,14 @@ public ReadOnlySpan<char> Format(LogMessage logMessage, LogFormatter formatter,
         var buffer = _charBuffer;
         Span<byte> span = buffer;
         int charsWritten;
-        while (!formatter.TryFormat(logMessage, MemoryMarshal.Cast<byte, char>(span), out charsWritten, ref segments))
+        while (true)
         {
+            segments.Reset();
+            if (formatter.TryFormat(logMessage, MemoryMarshal.Cast<byte, char>(span), out charsWritten, ref segments))
+            {
+                break;
+            }
+
             ArrayPool<byte>.Shared.Return(buffer);
             buffer = ArrayPool<byte>.Shared.Rent(span.Length * 2);
             span = buffer;