Reduce allocations under SyntaxNodeExtensions.GetContent

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Syntax/GreenNode.cs

@@ -8,7 +8,9 @@
 using System.Globalization;
 using System.IO;
 using System.Runtime.CompilerServices;
+using System.Text;
 using Microsoft.AspNetCore.Razor.PooledObjects;
+using Microsoft.Extensions.ObjectPool;
 
 namespace Microsoft.AspNetCore.Razor.Language.Syntax;
 
@@ -22,6 +24,12 @@ internal abstract class GreenNode
     private static readonly ConditionalWeakTable<GreenNode, SyntaxAnnotation[]> AnnotationsTable =
         new ConditionalWeakTable<GreenNode, SyntaxAnnotation[]>();
 
+    /// <summary>
+    /// Pool of StringWriters for use in <see cref="ToString()"/>. Users should not dispose the StringWriter directly
+    /// (but should dispose of the PooledObject returned from Pool.GetPooledObject).
+    /// </summary>
+    private static readonly ObjectPool<StringWriter> CurrentCultureStringWriterPool = DefaultPool.Create(Policy.Instance);
+
     private int _width;
     private byte _slotCount;
 
@@ -240,6 +248,15 @@ public override string ToString()
         return builder.ToString();
     }
 
+    internal string ToStringInCurrentCulture()
+    {
+        using var _ = CurrentCultureStringWriterPool.GetPooledObject(out var writer);
+
+        WriteTo(writer);
+
+        return writer.ToString();
+    }
+
     public void WriteTo(TextWriter writer)
     {
         // Use an actual Stack so we can write out deeply recursive structures without overflowing.
@@ -351,4 +368,30 @@ public SyntaxNode CreateRed()
     public abstract TResult Accept<TResult>(InternalSyntax.SyntaxVisitor<TResult> visitor);
 
     public abstract void Accept(InternalSyntax.SyntaxVisitor visitor);
+
+    private sealed class Policy : IPooledObjectPolicy<StringWriter>
+    {
+        public static readonly Policy Instance = new();
+
+        private Policy()
+        {
+        }
+
+        public StringWriter Create()
+            => new StringWriter(new StringBuilder());
+
+        public bool Return(StringWriter writer)
+        {
+            var builder = writer.GetStringBuilder();
+
+            // Very similar to StringBuilderPool.Policy implementation.
+            builder.Clear();
+            if (builder.Capacity > DefaultPool.MaximumObjectSize)
+            {
+                builder.Capacity = DefaultPool.MaximumObjectSize;
+            }
+
+            return true;
+        }
+    }
 }

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Syntax/SyntaxNodeExtensions.cs

@@ -6,7 +6,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.CodeAnalysis.CSharp;
 
 namespace Microsoft.AspNetCore.Razor.Language.Syntax;
@@ -303,11 +302,7 @@ public static TRoot InsertNodesAfter<TRoot>(this TRoot root, SyntaxNode nodeInLi
 
     public static string GetContent<TNode>(this TNode node) where TNode : SyntaxNode
     {
-        using var _ = StringBuilderPool.GetPooledObject(out var builder);
-        using var writer = new System.IO.StringWriter(builder);
-        node.Green.WriteTo(writer);
-
-        return writer.ToString();
+        return node.Green.ToStringInCurrentCulture();
     }
 
     private sealed class DiagnosticSyntaxWalker(List<RazorDiagnostic> diagnostics) : SyntaxWalker