Use tp_getattro for AttributeError suggestions instead of the __getattr__ hook (#126)

* Use tp_getattro instead of the miss-only __getattr__ hook

Reimplement the AttributeError member-name suggestions on top of a
ClassObject.tp_getattro override, replacing the miss-only __getattr__
hook (AttributeErrorHint) that was merged in #124.

The hook installed a shared __getattr__ on every reflected type and
manually rewired tp_getattro to CPython's slot_tp_getattr_hook. That
surgery is significantly more invasive for no measurable real-world
benefit: the per-access cost it avoids (~17 ns) is lost in the noise on
realistic Lean workloads. This version keeps the enrichment entirely in
a tp_getattro override that delegates to PyObject_GenericGetAttr and only
does work on a miss, and drops all the slot manipulation.

Behaviour and messages are unchanged (snake_case "Did you mean ...?"
suggestions); the existing Python and embedding tests are untouched and
still pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* Bump version to 2.0.56

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: jhonabreul

src/runtime/AttributeErrorHint.cs

@@ -5,7 +5,7 @@
     <RootNamespace>Python.Runtime</RootNamespace>
     <AssemblyName>Python.Runtime</AssemblyName>
     <PackageId>QuantConnect.pythonnet</PackageId>
-    <Version>2.0.55</Version>
+    <Version>2.0.56</Version>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
     <RepositoryUrl>https://github.com/pythonnet/pythonnet</RepositoryUrl>

src/runtime/Python.Runtime.csproj

@@ -263,10 +263,6 @@ public static void Initialize(IEnumerable<string> args, bool setSysArgv = true,
             }
 
             ImportHook.UpdateCLRModuleDict();
-
-            // Set up the miss-only __getattr__ hook used to enrich AttributeError
-            // messages on reflected .NET types with member-name suggestions.
-            AttributeErrorHint.Initialize();
         }
 
         static BorrowedReference DefineModule(string name)
@@ -373,9 +369,6 @@ public static void Shutdown()
             AppDomain.CurrentDomain.ProcessExit -= OnProcessExit;
 
             ExecuteShutdownHandlers();
-
-            AttributeErrorHint.Shutdown();
-
             // Remember to shut down the runtime.
             Runtime.Shutdown();
 

src/runtime/PythonEngine.cs

@@ -303,10 +303,6 @@ internal static void InitializeClass(PyType type, ClassBase impl, Type clrType)
 
             Runtime.PyType_Modified(type.Reference);
 
-            // Enrich AttributeError messages for missing attributes with member-name
-            // suggestions, via a miss-only __getattr__ hook (no hot-path cost).
-            AttributeErrorHint.Install(type.Reference);
-
             //DebugUtil.DumpType(type);
         }
 

src/runtime/TypeManager.cs

@@ -628,13 +628,20 @@ internal static void AppendAttributeErrorSuggestions(BorrowedReference ob, Borro
             }
 
             var name = Runtime.GetManagedString(key);
-            if (string.IsNullOrEmpty(name))
+            // Skip empty and dunder names: the latter are probed internally by CPython
+            // (e.g. __iter__, __len__) and are never user-facing typos worth helping with.
+            if (string.IsNullOrEmpty(name) || name.StartsWith("__", StringComparison.Ordinal))
             {
                 return;
             }
 
-            var hint = GetSuggestionHint(ob, name);
-            if (hint.Length == 0)
+            if (GetManagedObject(ob) is not CLRObject clrObj || clrObj.inst is null)
+            {
+                return;
+            }
+
+            var suggestions = GetSimilarMemberNames(clrObj.inst.GetType(), name);
+            if (suggestions.Count == 0)
             {
                 return;
             }
@@ -644,6 +651,7 @@ internal static void AppendAttributeErrorSuggestions(BorrowedReference ob, Borro
             try
             {
                 var baseMessage = GetErrorMessage(errValue.BorrowNullable(), name);
+                var hint = " Did you mean: " + string.Join(", ", suggestions.Select(s => $"'{s}'")) + "?";
                 Exceptions.SetError(Exceptions.AttributeError, baseMessage + hint);
             }
             finally
@@ -654,65 +662,6 @@ internal static void AppendAttributeErrorSuggestions(BorrowedReference ob, Borro
             }
         }
 
-        /// <summary>
-        /// Builds the full message for an <c>AttributeError</c> raised for a missing
-        /// attribute on a .NET object, including any "Did you mean ...?" hint. Used by
-        /// the miss-only <c>__getattr__</c> hook installed on reflected types (see
-        /// <see cref="AttributeErrorHint"/>), where the original error has already been
-        /// cleared, so the base message is reconstructed here.
-        /// </summary>
-        internal static string BuildMissingAttributeMessage(PyObject self, string name)
-        {
-            var typeName = "object";
-            try
-            {
-                using var pyType = self.GetPythonType();
-                typeName = pyType.Name;
-            }
-            catch
-            {
-                // fall back to the generic type name
-            }
-
-            var message = $"'{typeName}' object has no attribute '{name}'";
-            try
-            {
-                return message + GetSuggestionHint(self.Reference, name);
-            }
-            catch
-            {
-                // never let suggestion building turn into a different exception
-                return message;
-            }
-        }
-
-        /// <summary>
-        /// Returns " Did you mean: 'x', 'y'?" listing similarly-named members of the
-        /// managed object, or an empty string when there is nothing to suggest. Dunder
-        /// names are skipped: they are probed internally by CPython (e.g. __iter__,
-        /// __len__) and are never user-facing typos worth helping with.
-        /// </summary>
-        private static string GetSuggestionHint(BorrowedReference ob, string name)
-        {
-            if (string.IsNullOrEmpty(name) || name.StartsWith("__", StringComparison.Ordinal))
-            {
-                return string.Empty;
-            }
-
-            if (GetManagedObject(ob) is not CLRObject clrObj || clrObj.inst is null)
-            {
-                return string.Empty;
-            }
-
-            var suggestions = GetSimilarMemberNames(clrObj.inst.GetType(), name);
-            if (suggestions.Count == 0)
-            {
-                return string.Empty;
-            }
-
-            return " Did you mean: " + string.Join(", ", suggestions.Select(s => $"'{s}'")) + "?";
-        }
-
         private static string GetErrorMessage(BorrowedReference value, string fallbackName)
         {
             if (value != null)

src/runtime/Types/ClassBase.cs

@@ -167,6 +167,21 @@ public override void InitializeSlots(BorrowedReference pyType, SlotsHolder slots
         protected virtual NewReference NewObjectToPython(object obj, BorrowedReference tp)
             => CLRObject.GetReference(obj, tp);
 
+        /// <summary>
+        /// Type __getattro__ implementation. Delegates to the generic CLR attribute
+        /// lookup, but enriches the AttributeError raised for a missing attribute with
+        /// suggestions of similarly-named members of the managed type.
+        /// </summary>
+        public static NewReference tp_getattro(BorrowedReference ob, BorrowedReference key)
+        {
+            var result = Runtime.PyObject_GenericGetAttr(ob, key);
+            if (result.IsNull())
+            {
+                AppendAttributeErrorSuggestions(ob, key);
+            }
+            return result;
+        }
+
         private static NewReference NewEnum(Type type, BorrowedReference args, BorrowedReference tp)
         {
             nint argCount = Runtime.PyTuple_Size(args);