Emit AttributeError member suggestions in snake_case

The fork exposes .NET members under PEP8-style snake_case aliases, so the
"Did you mean ...?" suggestions now use that form (e.g. 'length' instead
of 'Length'). Conversion reuses the existing ToSnakeCase helpers, so const
and static-readonly members are rendered UPPER_CASE to match how they are
exposed to Python.

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

Author: jhonabreul

src/embed_tests/TestPropertyAccess.cs

@@ -1142,8 +1142,9 @@ from Python.EmbeddingTest import *
 class TestGetMisspelledDynamicObjectPropertySuggestsSimilarMembers:
     def GetValue(self, fixture):
         try:
-            # 'NonDynamicPropertyy' is a near miss of the real 'NonDynamicProperty' member.
-            prop = fixture.NonDynamicPropertyy
+            # 'non_dynamic_propertyy' is a near miss of the snake_case alias of the
+            # real 'NonDynamicProperty' member.
+            prop = fixture.non_dynamic_propertyy
         except AttributeError as e:
             return e
 
@@ -1158,10 +1159,11 @@ def GetValue(self, fixture):
                 Assert.IsFalse(result.IsNone());
                 Assert.AreEqual(result.PyType, Exceptions.AttributeError);
 
+                // Suggestions are emitted in snake_case, matching the fork's PEP8-style API.
                 var message = result.ToString();
-                Assert.That(message, Does.Contain("NonDynamicPropertyy"));
+                Assert.That(message, Does.Contain("non_dynamic_propertyy"));
                 Assert.That(message, Does.Contain("Did you mean"));
-                Assert.That(message, Does.Contain("NonDynamicProperty"));
+                Assert.That(message, Does.Contain("non_dynamic_property"));
             }
         }
 

src/runtime/Types/ClassBase.cs

@@ -700,8 +700,15 @@ private static List<string> GetSimilarMemberNames(Type type, string name)
                     continue;
                 }
 
-                string candidate = member.Name;
-                if (candidate.Length == 0 || candidate[0] == '<' || !seen.Add(candidate))
+                if (member.Name.Length == 0 || member.Name[0] == '<')
+                {
+                    continue;
+                }
+
+                // Suggest the snake_case alias, since that is the fork's PEP8-style
+                // public API surface (members are exposed in both Pascal and snake case).
+                string candidate = ToSnakeCaseMemberName(member);
+                if (!seen.Add(candidate))
                 {
                     continue;
                 }
@@ -724,6 +731,18 @@ private static List<string> GetSimilarMemberNames(Type type, string name)
                 .ToList();
         }
 
+        private static string ToSnakeCaseMemberName(MemberInfo member)
+        {
+            // Use the field/property overloads so const and static-readonly members
+            // are converted to UPPER_CASE, matching how they are exposed to Python.
+            return member switch
+            {
+                FieldInfo fieldInfo => fieldInfo.ToSnakeCase(),
+                PropertyInfo propertyInfo => propertyInfo.ToSnakeCase(),
+                _ => member.Name.ToSnakeCase(),
+            };
+        }
+
         private static int LevenshteinDistance(string a, string b)
         {
             a = a.ToLowerInvariant();

tests/test_class.py

@@ -67,17 +67,21 @@ def test_non_exported():
 
 
 def test_missing_attribute_suggests_similar_members():
-    """A missing attribute on a .NET object should suggest similarly-named members."""
+    """A missing attribute on a .NET object should suggest similarly-named members.
+
+    Suggestions are emitted in snake_case, matching the fork's PEP8-style API.
+    """
     s = System.String("this is a test")
 
-    # 'Lenght' is a transposition of 'Length' (a real member), so it should be suggested.
+    # 'lenght' is a transposition of 'length' (the snake_case alias of the real
+    # 'Length' member), so it should be suggested.
     with pytest.raises(AttributeError) as exc_info:
-        _ = s.Lenght
+        _ = s.lenght
 
     message = str(exc_info.value)
-    assert "Lenght" in message
+    assert "lenght" in message
     assert "Did you mean" in message
-    assert "Length" in message
+    assert "length" in message
 
 
 def test_missing_attribute_no_similar_members():