Removed allocations for timestamp

src/Serilog.Expressions/Templates/Compilation/CompiledTimestampToken.cs

@@ -0,0 +1,70 @@
+// Copyright © Serilog Contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using Serilog.Expressions;
+using Serilog.Parsing;
+using Serilog.Templates.Rendering;
+using Serilog.Templates.Themes;
+
+namespace Serilog.Templates.Compilation;
+
+class CompiledTimestampToken : CompiledTemplate
+{
+    readonly string? _format;
+    readonly Alignment? _alignment;
+    readonly IFormatProvider? _formatProvider;
+    readonly Style _secondaryText;
+
+    public CompiledTimestampToken(string? format, Alignment? alignment, IFormatProvider? formatProvider, TemplateTheme theme)
+    {
+        _format = format;
+        _alignment = alignment;
+        _formatProvider = formatProvider;
+        _secondaryText = theme.GetStyle(TemplateThemeStyle.SecondaryText);
+    }
+
+    public override void Evaluate(EvaluationContext ctx, TextWriter output)
+    {
+        var invisibleCharacterCount = 0;
+
+        if (_alignment == null)
+        {
+            EvaluateUnaligned(ctx, output, _formatProvider, ref invisibleCharacterCount);
+        }
+        else
+        {
+            var writer = new StringWriter();
+            EvaluateUnaligned(ctx, writer, _formatProvider, ref invisibleCharacterCount);
+            Padding.Apply(output, writer.ToString(), _alignment.Value.Widen(invisibleCharacterCount));
+        }
+    }
+
+    void EvaluateUnaligned(EvaluationContext ctx, TextWriter output, IFormatProvider? formatProvider, ref int invisibleCharacterCount)
+    {
+        var value = ctx.LogEvent.Timestamp;
+
+        using var style = _secondaryText.Set(output, ref invisibleCharacterCount);
+
+#if FEATURE_SPAN
+        Span<char> buffer = stackalloc char[36];
+        if (value.TryFormat(buffer, out int charsWritten, _format, _formatProvider))
+        {
+            output.Write(buffer[..charsWritten]);
+            return;
+        }
+#endif
+        output.Write(value.ToString(_format, formatProvider));
+
+    }
+}

src/Serilog.Expressions/Templates/Compilation/TemplateCompiler.cs

@@ -44,6 +44,10 @@ public static CompiledTemplate Compile(Template template,
                 Expression: AmbientNameExpression { IsBuiltIn: true, PropertyName: BuiltInProperty.Message },
                 Format: null
             } message => encoder.Wrap(new CompiledMessageToken(formatProvider, message.Alignment, theme)),
+            FormattedExpression
+            {
+                Expression: AmbientNameExpression { IsBuiltIn: true, PropertyName: BuiltInProperty.Timestamp },
+            } timestamp => encoder.Wrap(new CompiledTimestampToken(timestamp.Format, timestamp.Alignment, formatProvider, theme)),
             FormattedExpression expression => encoder.MakeCompiledFormattedExpression(
                 ExpressionCompiler.Compile(expression.Expression, formatProvider, nameResolver), expression.Format, expression.Alignment, formatProvider, theme),
             TemplateBlock block => new CompiledTemplateBlock(block.Elements.Select(e => Compile(e, formatProvider, nameResolver, theme, encoder)).ToArray()),

test/Serilog.Expressions.Tests/Cases/template-evaluation-cases.asv

@@ -33,3 +33,5 @@ Culture-specific {42.34}                             ⇶ Culture-specific 42,34
 {rest()}                                             ⇶ {"Name":"nblumhardt"}
 {Name} {rest()}                                      ⇶ nblumhardt {}
 {rest(true)}                                         ⇶ {}
+{@t:yyyy-MM-dd HH:mm:ss.ffff zzz}                    ⇶ 2000-12-31 23:59:58.1230 +10:00
+{@t:yyyy-MM-dd HH:mm:ss.ffff zzz------------------}  ⇶ 2000-12-31 23:59:58.1230 +10:00------------------

test/Serilog.Expressions.Tests/Support/Some.cs

@@ -12,12 +12,22 @@ public static LogEvent InformationEvent(string messageTemplate = "Hello, world!"
         return LogEvent(LogEventLevel.Information, messageTemplate, propertyValues);
     }
 
+    public static LogEvent InformationEvent(DateTimeOffset timestamp, string messageTemplate = "Hello, world!", params object?[] propertyValues)
+    {
+        return LogEvent(timestamp, LogEventLevel.Information, messageTemplate, propertyValues);
+    }
+
     public static LogEvent WarningEvent(string messageTemplate = "Hello, world!", params object?[] propertyValues)
     {
         return LogEvent(LogEventLevel.Warning, messageTemplate, propertyValues);
     }
 
     public static LogEvent LogEvent(LogEventLevel level, string messageTemplate = "Hello, world!", params object?[] propertyValues)
+    {
+        return LogEvent(DateTimeOffset.Now, level, messageTemplate, propertyValues);
+    }
+
+    public static LogEvent LogEvent(DateTimeOffset timestamp, LogEventLevel level, string messageTemplate = "Hello, world!", params object?[] propertyValues)
     {
         var log = new LoggerConfiguration().CreateLogger();
 #pragma warning disable Serilog004 // Constant MessageTemplate verifier
@@ -26,7 +36,7 @@ public static LogEvent LogEvent(LogEventLevel level, string messageTemplate = "H
         {
             throw new XunitException("Template could not be bound.");
         }
-        return new(DateTimeOffset.Now, level, null, template, properties);
+        return new(timestamp, level, null, template, properties);
     }
 
     public static object AnonymousObject()

test/Serilog.Expressions.Tests/TemplateEvaluationTests.cs

@@ -1,4 +1,5 @@
 using System.Globalization;
+using Serilog.Events;
 using Serilog.Expressions.Tests.Support;
 using Serilog.Templates;
 using Xunit;
@@ -7,14 +8,17 @@ namespace Serilog.Expressions.Tests;
 
 public class TemplateEvaluationTests
 {
+    static readonly DateTimeOffset TestTimestamp = new(
+        2000, 12, 31, 23, 59, 58, 123, TimeSpan.FromHours(10));
+
     public static IEnumerable<object[]> TemplateEvaluationCases =>
         AsvCases.ReadCases("template-evaluation-cases.asv");
 
     [Theory]
     [MemberData(nameof(TemplateEvaluationCases))]
     public void TemplatesAreCorrectlyEvaluated(string template, string expected)
     {
-        var evt = Some.InformationEvent("Hello, {Name}!", "nblumhardt");
+        var evt = Some.InformationEvent(TestTimestamp, "Hello, {Name}!", "nblumhardt");
         var frFr = CultureInfo.GetCultureInfoByIetfLanguageTag("fr-FR");
         var compiled = new ExpressionTemplate(template, formatProvider: frFr);
         var output = new StringWriter();