gh-137967: Restore suggestions on nested attribute access

Author: pablogsal

Lib/test/test_traceback.py

@@ -4262,6 +4262,87 @@ def __getattribute__(self, attr):
         self.assertIn("Did you mean", actual)
         self.assertIn("bluch", actual)
 
+    def test_getattr_nested_attribute_suggestions(self):
+        # Test that nested attributes are suggested when no direct match
+        class Inner:
+            def __init__(self):
+                self.value = 42
+                self.data = "test"
+
+        class Outer:
+            def __init__(self):
+                self.inner = Inner()
+
+        # Should suggest 'inner.value'
+        actual = self.get_suggestion(Outer(), 'value')
+        self.assertIn("Did you mean: 'inner.value'", actual)
+
+        # Should suggest 'inner.data'
+        actual = self.get_suggestion(Outer(), 'data')
+        self.assertIn("Did you mean: 'inner.data'", actual)
+
+    def test_getattr_nested_prioritizes_direct_matches(self):
+        # Test that direct attribute matches are prioritized over nested ones
+        class Inner:
+            def __init__(self):
+                self.foo = 42
+
+        class Outer:
+            def __init__(self):
+                self.inner = Inner()
+                self.fooo = 100  # Similar to 'foo'
+
+        # Should suggest 'fooo' (direct) not 'inner.foo' (nested)
+        actual = self.get_suggestion(Outer(), 'foo')
+        self.assertIn("Did you mean: 'fooo'", actual)
+        self.assertNotIn("inner.foo", actual)
+
+    def test_getattr_nested_with_property(self):
+        # Test nested suggestions work with properties
+        class Inner:
+            @property
+            def computed(self):
+                return 42
+
+        class Outer:
+            def __init__(self):
+                self.inner = Inner()
+
+        actual = self.get_suggestion(Outer(), 'computed')
+        self.assertIn("Did you mean: 'inner.computed'", actual)
+
+    def test_getattr_nested_no_suggestion_for_deep_nesting(self):
+        # Test that deeply nested attributes (2+ levels) are not suggested
+        class Deep:
+            def __init__(self):
+                self.value = 42
+
+        class Middle:
+            def __init__(self):
+                self.deep = Deep()
+
+        class Outer:
+            def __init__(self):
+                self.middle = Middle()
+
+        # Should not suggest 'middle.deep.value' (too deep)
+        actual = self.get_suggestion(Outer(), 'value')
+        self.assertNotIn("Did you mean", actual)
+
+    def test_getattr_nested_ignores_private_attributes(self):
+        # Test that nested suggestions ignore private attributes
+        class Inner:
+            def __init__(self):
+                self.public_value = 42
+
+        class Outer:
+            def __init__(self):
+                self._private_inner = Inner()
+
+        # Should not suggest '_private_inner.public_value'
+        actual = self.get_suggestion(Outer(), 'public_value')
+        self.assertNotIn("Did you mean", actual)
+
     def make_module(self, code):
         tmpdir = Path(tempfile.mkdtemp())
         self.addCleanup(shutil.rmtree, tmpdir)

Lib/traceback.py

@@ -1601,6 +1601,31 @@ def _substitution_cost(ch_a, ch_b):
     return _MOVE_COST
 
 
+def _check_for_nested_attribute(obj, wrong_name, attrs):
+    """Check if any attribute of obj has the wrong_name as a nested attribute.
+    
+    Returns the first nested attribute suggestion found, or None.
+    Limited to checking 20 attributes and returning up to 5 suggestions.
+    """
+    nested_suggestions = []
+    max_nested_suggestions = 5
+    
+    # Check for nested attributes (only one level deep)
+    attrs_to_check = [x for x in attrs if not x.startswith('_')][:20]  # Limit number of attributes to check
+    for attr_name in attrs_to_check:
+        try:
+            attr_obj = getattr(obj, attr_name)
+            # Check if the nested attribute has the wrong_name
+            if hasattr(attr_obj, wrong_name):
+                nested_suggestions.append(f"{attr_name}.{wrong_name}")
+                if len(nested_suggestions) >= max_nested_suggestions:
+                    break
+        except:
+            pass
+    
+    return nested_suggestions[0] if nested_suggestions else None
+
+
 def _compute_suggestion_error(exc_value, tb, wrong_name):
     if wrong_name is None or not isinstance(wrong_name, str):
         return None
@@ -1666,7 +1691,9 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
     except ImportError:
         pass
     else:
-        return _suggestions._generate_suggestions(d, wrong_name)
+        suggestion = _suggestions._generate_suggestions(d, wrong_name)
+        if suggestion:
+            return suggestion
 
     # Compute closest match
 
@@ -1691,6 +1718,16 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
         if not suggestion or current_distance < best_distance:
             suggestion = possible_name
             best_distance = current_distance
+    
+    # If no direct attribute match found, check for nested attributes
+    if not suggestion and isinstance(exc_value, AttributeError):
+        try:
+            nested_suggestion = _check_for_nested_attribute(exc_value.obj, wrong_name, d)
+            if nested_suggestion:
+                return nested_suggestion
+        except:
+            pass
+    
     return suggestion
 
 

Misc/NEWS.d/next/Core_and_Builtins/2025-08-19-18-52-22.gh-issue-137967.uw67Ys.rst

@@ -0,0 +1 @@
+Show error suggestions on nested attribute access. Patch by Pablo Galindo