From 0e17105912573788c3c20c23df13bdfe5c10f5b6 Mon Sep 17 00:00:00 2001
From: Abdelghani Moussaid
 <20841568+abdelghani-moussaid@users.noreply.github.com>
Date: Thu, 14 May 2026 22:31:12 +0100
Subject: [PATCH] perf: reduce TreeNodeFilter allocations via IReadOnlyList and
 ReadOnlySpan

- Widen SubExpressions to IReadOnlyList to enable optimized LINQ paths.
- Implement ReadOnlySpan-based matching for .NET 8.0+ to eliminate
  string fragment allocations.
- Use procedural loops in Span path to avoid ref-struct capture (CS9108).
---
 .../TreeNodeFilter/OperatorExpression.cs      |  4 +-
 .../Requests/TreeNodeFilter/TreeNodeFilter.cs | 50 +++++++++++++++++++
 2 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/OperatorExpression.cs b/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/OperatorExpression.cs
index cf5409e595..0333f7e048 100644
--- a/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/OperatorExpression.cs
+++ b/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/OperatorExpression.cs
@@ -4,9 +4,9 @@
 namespace Microsoft.Testing.Platform.Requests;
 
 // Allows to express an expression A & B or A | B
-internal sealed class OperatorExpression(FilterOperator op, IReadOnlyCollection<FilterExpression> subExpressions) : FilterExpression
+internal sealed class OperatorExpression(FilterOperator op, IReadOnlyList<FilterExpression> subExpressions) : FilterExpression
 {
     public FilterOperator Op { get; } = op;
 
-    public IReadOnlyCollection<FilterExpression> SubExpressions { get; } = subExpressions;
+    public IReadOnlyList<FilterExpression> SubExpressions { get; } = subExpressions;
 }
diff --git a/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/TreeNodeFilter.cs b/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/TreeNodeFilter.cs
index da7178a629..c10e2bb94c 100644
--- a/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/TreeNodeFilter.cs
+++ b/src/Platform/Microsoft.Testing.Platform/Requests/TreeNodeFilter/TreeNodeFilter.cs
@@ -542,10 +542,60 @@ private static bool MatchFilterPattern(
         int endFragmentIndex,
         PropertyBag properties)
     {
+#if NET8_0_OR_GREATER
+        return MatchFilterPattern(
+            filterExpression,
+            testNodeFullPath.AsSpan(startFragmentIndex, endFragmentIndex - startFragmentIndex),
+            properties);
+#else
         string str = testNodeFullPath[startFragmentIndex..endFragmentIndex];
         return MatchFilterPattern(filterExpression, str, properties);
+#endif
     }
 
+#if NET8_0_OR_GREATER
+    private static bool MatchFilterPattern(
+        FilterExpression filterExpression,
+        ReadOnlySpan<char> testNodeFragment,
+        PropertyBag properties)
+    {
+        switch (filterExpression)
+        {
+            case ValueExpression vExpr:
+                return vExpr.Regex.IsMatch(testNodeFragment);
+            case OperatorExpression { Op: FilterOperator.Or, SubExpressions: var subexprs }:
+                foreach (FilterExpression expr in subexprs)
+                {
+                    if (MatchFilterPattern(expr, testNodeFragment, properties))
+                    {
+                        return true;
+                    }
+                }
+
+                return false;
+            case OperatorExpression { Op: FilterOperator.And, SubExpressions: var subexprs }:
+                foreach (FilterExpression expr in subexprs)
+                {
+                    if (!MatchFilterPattern(expr, testNodeFragment, properties))
+                    {
+                        return false;
+                    }
+                }
+
+                return true;
+            case OperatorExpression { Op: FilterOperator.Not, SubExpressions: var subexprs }:
+                return !MatchFilterPattern(subexprs.Single(), testNodeFragment, properties);
+            case ValueAndPropertyExpression { Value: var valueExpr, Properties: var propExpr }:
+                return MatchFilterPattern(valueExpr, testNodeFragment, properties)
+                    && MatchProperties(propExpr, properties);
+            case NopExpression:
+                return true;
+            default:
+                throw ApplicationStateGuard.Unreachable();
+        }
+    }
+#endif
+
     private static bool MatchFilterPattern(
         FilterExpression filterExpression,
         string testNodeFragment,