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thomhurst merged 2 commits into from
May 28, 2026
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perf(engine): reduce allocations in reflection-mode discovery/execution #6113

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571c38c
perf(engine): reduce allocations in reflection-mode discovery/execution
thomhurst May 28, 2026
3c74a2a
refactor(engine): address PR review on reflection-alloc perf pass
thomhurst May 28, 2026
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53 changes: 47 additions & 6 deletions TUnit.Engine/Building/ReflectionMetadataBuilder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,15 +26,56 @@ public static MethodMetadata CreateMethodMetadata(
Type = type,
TypeInfo = CreateTypeInfo(type),
Class = CreateClassMetadata(type),
Parameters = method.GetParameters()
.Select((p, i) => CreateParameterMetadata(p.ParameterType, p.Name ?? "unnamed", i, p))
.ToArray(),
Parameters = BuildParameterMetadata(method.GetParameters()),
GenericTypeCount = method.IsGenericMethodDefinition ? method.GetGenericArguments().Length : 0,
ReturnTypeInfo = CreateTypeInfo(method.ReturnType),
ReturnType = method.ReturnType
};
}

#if NET8_0_OR_GREATER
[RequiresUnreferencedCode("Parameter metadata creation uses reflection")]
#endif
private static ParameterMetadata[] BuildParameterMetadata(System.Reflection.ParameterInfo[] parameters)
{
if (parameters.Length == 0)
{
return [];
}

var result = new ParameterMetadata[parameters.Length];
for (var i = 0; i < parameters.Length; i++)
{
var p = parameters[i];
result[i] = CreateParameterMetadata(p.ParameterType, p.Name ?? "unnamed", i, p);
}

return result;
}

#if NET8_0_OR_GREATER
[RequiresUnreferencedCode("Parameter metadata creation uses reflection")]
#endif
private static ParameterMetadata[] BuildConstructorParameterMetadata(System.Reflection.ParameterInfo[] parameters)
{
if (parameters.Length == 0)
{
return [];
}

var result = new ParameterMetadata[parameters.Length];
for (var i = 0; i < parameters.Length; i++)
{
var p = parameters[i];
// Preserve original behaviour: ctor parameters pass p.Name through unchanged
// (CreateParameterMetadata falls back to "param{index}" when null), unlike method
// parameters which fall back to "unnamed".
result[i] = CreateParameterMetadata(p.ParameterType, p.Name, i, p);
}

return result;
}

private static TypeInfo CreateTypeInfo(Type type)
{
return new ConcreteType(type);
Expand Down Expand Up @@ -74,9 +115,9 @@ private static ClassMetadata CreateClassMetadata([DynamicallyAccessedMembers(Dyn
var constructors = type.GetConstructors(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance);
var constructor = constructors.FirstOrDefault();

var constructorParameters = constructor?.GetParameters()
.Select((p, i) => CreateParameterMetadata(p.ParameterType, p.Name, i, p))
.ToArray() ?? [];
var constructorParameters = constructor is null
? []
: BuildConstructorParameterMetadata(constructor.GetParameters());

return new ClassMetadata
{
Expand Down
14 changes: 8 additions & 6 deletions TUnit.Engine/Discovery/ConstructorHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,16 +21,18 @@ internal static class ConstructorHelper
{
var constructors = testClass.GetConstructors(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);

// First, look for constructors marked with [TestConstructor]
var testConstructorMarked = constructors.Where(c => c.GetCustomAttribute<TestConstructorAttribute>() != null).ToArray();

if (testConstructorMarked.Length > 0)
// First, look for the first constructor marked with [TestConstructor] (stop early instead
// of building a filtered array just to read index 0).
foreach (var constructor in constructors)
{
return testConstructorMarked[0];
if (constructor.GetCustomAttribute<TestConstructorAttribute>() != null)
{
return constructor;
}
}

// If no [TestConstructor] attribute found, return the first instance constructor
return constructors.FirstOrDefault();
return constructors.Length > 0 ? constructors[0] : null;
}

/// <summary>
Expand Down
82 changes: 59 additions & 23 deletions TUnit.Engine/Discovery/ReflectionHookDiscoveryService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -128,25 +128,32 @@ public static void DiscoverInstanceHooksForType(Type closedGenericType)
// Discover hooks in each type in the inheritance chain, from base to derived
foreach (var typeInChain in inheritanceChain)
{
var methods = typeInChain.GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly)
.OrderBy(m =>
{
// Get the minimum order from cached hook attributes
var (beforeAttr, afterAttr, beforeEveryAttr, afterEveryAttr) = GetCachedAttributes(m);
var declaredMethods = typeInChain.GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly);

// Pre-compute the sort keys once (the old OrderBy lambda allocated a List<int> and
// recomputed attributes on every comparison). Sort by minimum hook order, then by
// MetadataToken to preserve source-file order. MetadataToken is unique per method
// within a type, so the (order, token) key is total — Array.Sort needs no extra
// stability guarantee to reproduce the previous OrderBy/ThenBy result.
var sortKeys = new HookMethodSortKey[declaredMethods.Length];
for (var i = 0; i < declaredMethods.Length; i++)
{
var m = declaredMethods[i];
var (beforeAttr, afterAttr, beforeEveryAttr, afterEveryAttr) = GetCachedAttributes(m);

var orders = new List<int>();
if (beforeAttr != null) orders.Add(beforeAttr.Order);
if (afterAttr != null) orders.Add(afterAttr.Order);
if (beforeEveryAttr != null) orders.Add(beforeEveryAttr.Order);
if (afterEveryAttr != null) orders.Add(afterEveryAttr.Order);
var hasOrder = false;
var minOrder = 0;
if (beforeAttr != null) { minOrder = beforeAttr.Order; hasOrder = true; }
if (afterAttr != null) { minOrder = hasOrder ? Math.Min(minOrder, afterAttr.Order) : afterAttr.Order; hasOrder = true; }
if (beforeEveryAttr != null) { minOrder = hasOrder ? Math.Min(minOrder, beforeEveryAttr.Order) : beforeEveryAttr.Order; hasOrder = true; }
if (afterEveryAttr != null) { minOrder = hasOrder ? Math.Min(minOrder, afterEveryAttr.Order) : afterEveryAttr.Order; }

// Use Count instead of Any() to avoid double enumeration
return orders.Count > 0 ? orders.Min() : 0;
})
.ThenBy(static m => m.MetadataToken) // Then sort by MetadataToken to preserve source file order
.ToArray();
sortKeys[i] = new HookMethodSortKey(hasOrder ? minOrder : 0, m.MetadataToken);
}

foreach (var method in methods)
Array.Sort(sortKeys, declaredMethods);

foreach (var method in declaredMethods)
{
// Check for Before attributes
var beforeAttributes = method.GetCustomAttributes<BeforeAttribute>(false);
Expand Down Expand Up @@ -847,20 +854,49 @@ private static MethodMetadata CreateMethodMetadata(
Name = method.Name,
Type = type,
Class = CreateClassMetadata(type),
Parameters = method.GetParameters().Select(p => new ParameterMetadata(p.ParameterType)
{
Name = p.Name ?? string.Empty,
Type = p.ParameterType,
TypeInfo = new ConcreteType(p.ParameterType),
ReflectionInfo = p
}).ToArray(),
Parameters = BuildParameterMetadata(method.GetParameters()),
GenericTypeCount = 0,
ReturnTypeInfo = new ConcreteType(method.ReturnType),
ReturnType = method.ReturnType,
TypeInfo = new ConcreteType(type)
};
}

private readonly struct HookMethodSortKey(int order, int metadataToken) : IComparable<HookMethodSortKey>
{
private readonly int _order = order;
private readonly int _metadataToken = metadataToken;

public int CompareTo(HookMethodSortKey other)
{
var orderComparison = _order.CompareTo(other._order);
return orderComparison != 0 ? orderComparison : _metadataToken.CompareTo(other._metadataToken);
}
}

private static ParameterMetadata[] BuildParameterMetadata(ParameterInfo[] parameters)
{
if (parameters.Length == 0)
{
return [];
}

var result = new ParameterMetadata[parameters.Length];
for (var i = 0; i < parameters.Length; i++)
{
var p = parameters[i];
result[i] = new ParameterMetadata(p.ParameterType)
{
Name = p.Name ?? string.Empty,
Type = p.ParameterType,
TypeInfo = new ConcreteType(p.ParameterType),
ReflectionInfo = p
};
}

return result;
}

private static ClassMetadata CreateClassMetadata(Type type)
{
return ClassMetadata.GetOrAdd(type.FullName ?? type.Name, () => new ClassMetadata
Expand Down
135 changes: 82 additions & 53 deletions TUnit.Engine/Discovery/ReflectionTestDataCollector.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -300,7 +300,7 @@ private static bool ShouldScanAssembly(Assembly assembly)
return false;
}

if (name.EndsWith(".resources") || name.EndsWith(".XmlSerializers"))
if (name.EndsWith(".resources", StringComparison.Ordinal) || name.EndsWith(".XmlSerializers", StringComparison.Ordinal))
{
return false;
}
Expand Down Expand Up @@ -333,7 +333,7 @@ private static bool ShouldScanAssembly(Assembly assembly)
var hasTUnitReference = false;
foreach (var reference in referencedAssemblies)
{
if (reference.Name != null && (reference.Name.StartsWith("TUnit") || reference.Name == "TUnit"))
if (reference.Name != null && (reference.Name.StartsWith("TUnit", StringComparison.Ordinal) || reference.Name == "TUnit"))
{
hasTUnitReference = true;
break;
Expand All @@ -348,6 +348,45 @@ private static bool ShouldScanAssembly(Assembly assembly)
return true;
}

/// <summary>
/// Filters the non-null entries out of <see cref="ReflectionTypeLoadException.Types"/>, using a
/// pooled scratch buffer to avoid the per-failure allocations of the old LINQ Where().ToArray().
/// Shared by both the eager and streaming discovery type caches.
/// </summary>
private static Type[] FilterLoadedTypes(Type?[]? loadedTypes)
{
if (loadedTypes is null || loadedTypes.Length == 0)
{
return [];
}

var tempArray = ArrayPool<Type>.Shared.Rent(loadedTypes.Length);
try
{
var validCount = 0;
foreach (var type in loadedTypes)
{
if (type != null)
{
tempArray[validCount++] = type;
}
}

if (validCount == 0)
{
return [];
}

var result = new Type[validCount];
Array.Copy(tempArray, result, validCount);
return result;
}
finally
{
ArrayPool<Type>.Shared.Return(tempArray);
}
}

private static async Task<List<TestMetadata>> DiscoverTestsInAssembly(Assembly assembly)
{
var discoveredTests = new List<TestMetadata>(100);
Expand All @@ -360,7 +399,7 @@ private static async Task<List<TestMetadata>> DiscoverTestsInAssembly(Assembly a
}
catch (ReflectionTypeLoadException reflectionTypeLoadException)
{
return reflectionTypeLoadException.Types.Where(static x => x != null).ToArray()!;
return FilterLoadedTypes(reflectionTypeLoadException.Types);
}
catch (Exception)
{
Expand Down Expand Up @@ -475,35 +514,8 @@ private static async IAsyncEnumerable<TestMetadata> DiscoverTestsInAssemblyStrea
}
catch (ReflectionTypeLoadException rtle)
{
// Some types might fail to load, but we can still use the ones that loaded successfully
// Optimize: Manual filtering with ArrayPool for better memory efficiency
var loadedTypes = rtle.Types;
if (loadedTypes == null)
{
return [];
}

// Use ArrayPool for temporary storage to reduce allocations
var tempArray = ArrayPool<Type>.Shared.Rent(loadedTypes.Length);
try
{
var validCount = 0;
foreach (var type in loadedTypes)
{
if (type != null)
{
tempArray[validCount++] = type;
}
}

var result = new Type[validCount];
Array.Copy(tempArray, result, validCount);
return result;
}
finally
{
ArrayPool<Type>.Shared.Return(tempArray);
}
// Some types might fail to load, but we can still use the ones that loaded successfully.
return FilterLoadedTypes(rtle.Types);
}
catch (Exception)
{
Expand Down Expand Up @@ -1659,39 +1671,56 @@ private static bool IsCovariantCompatible(Type paramType, [DynamicallyAccessedMe

var paramGenericDef = paramType.GetGenericTypeDefinition();

// List of known covariant interfaces
var covariantInterfaces = new[]
{
typeof(IEnumerable<>),
typeof(IReadOnlyList<>),
typeof(IReadOnlyCollection<>),
typeof(IEnumerator<>)
};

if (!covariantInterfaces.Contains(paramGenericDef))
if (Array.IndexOf(CovariantInterfaces, paramGenericDef) < 0)
{
return false;
}

// Check the argument type's interfaces, plus the argument type itself when it's an interface,
// without allocating a combined array (the old Concat([argType]).ToArray() per call).
var argInterfaces = AssemblyReferenceCache.GetInterfaces(argType);
if (argType.IsInterface)
foreach (var iface in argInterfaces)
{
argInterfaces = argInterfaces.Concat([argType]).ToArray();
if (MatchesCovariantInterface(paramType, paramGenericDef, iface, out var compatible))
{
return compatible;
}
}

foreach (var iface in argInterfaces)
if (argType.IsInterface && MatchesCovariantInterface(paramType, paramGenericDef, argType, out var argCompatible))
{
if (iface.IsGenericType && iface.GetGenericTypeDefinition() == paramGenericDef)
{
var paramElementType = paramType.GetGenericArguments()[0];
var argElementType = iface.GetGenericArguments()[0];
return argCompatible;
}

// For covariance to work, the parameter element type must be assignable from the argument element type
// This allows IEnumerable<int> to be passed where IEnumerable<object> is expected
return paramElementType.IsAssignableFrom(argElementType);
}
return false;
}

/// <summary>
/// Known covariant generic interface definitions. Hoisted to avoid allocating the array per
/// <see cref="IsCovariantCompatible"/> call.
/// </summary>
private static readonly Type[] CovariantInterfaces =
[
typeof(IEnumerable<>),
typeof(IReadOnlyList<>),
typeof(IReadOnlyCollection<>),
typeof(IEnumerator<>)
];

private static bool MatchesCovariantInterface(Type paramType, Type paramGenericDef, Type iface, out bool compatible)
{
if (iface.IsGenericType && iface.GetGenericTypeDefinition() == paramGenericDef)
{
var paramElementType = paramType.GetGenericArguments()[0];
var argElementType = iface.GetGenericArguments()[0];

// For covariance to work, the parameter element type must be assignable from the argument element type
// This allows IEnumerable<int> to be passed where IEnumerable<object> is expected
compatible = paramElementType.IsAssignableFrom(argElementType);
return true;
}

compatible = false;
return false;
}

Expand Down
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