Fix crash on Super.getattr for previously uninferable attributes (#1370)

Co-authored-by: Pierre Sassoulas <[email protected]>

Author: DanielNoord

ChangeLog

@@ -9,6 +9,12 @@ Release date: TBA
 * Fixed builtin inferenence on `property` calls not calling the `postinit` of the new node, which
   resulted in instance arguments missing on these nodes.
 
+* Fixed a crash on ``Super.getattr`` when the attribute was previously uninferable due to a cache
+  limit size. This limit can be hit when the inheritance pattern of a class (and therefore of the
+  ``__init__`` attribute) is very large.
+
+  Closes PyCQA/pylint#5679
+
 What's New in astroid 2.9.4?
 ============================
 Release date: TBA

astroid/nodes/node_ng.py

@@ -163,7 +163,9 @@ def infer(self, context=None, **kwargs):
         limit = AstroidManager().max_inferable_values
         for i, result in enumerate(generator):
             if i >= limit or (context.nodes_inferred > context.max_inferred):
-                yield util.Uninferable
+                uninferable = util.Uninferable
+                results.append(uninferable)
+                yield uninferable
                 break
             results.append(result)
             yield result

tests/resources.py

@@ -13,14 +13,15 @@
 
 import os
 import sys
+from pathlib import Path
 from typing import Optional
 
 from astroid import builder
 from astroid.manager import AstroidManager
 from astroid.nodes.scoped_nodes import Module
 
-DATA_DIR = os.path.join("testdata", "python3")
-RESOURCE_PATH = os.path.join(os.path.dirname(__file__), DATA_DIR, "data")
+DATA_DIR = Path("testdata") / "python3"
+RESOURCE_PATH = Path(__file__).parent / DATA_DIR / "data"
 
 
 def find(name: str) -> str:

tests/testdata/python3/data/max_inferable_limit_for_classes/main.py

@@ -0,0 +1,38 @@
+"""This example is based on sqlalchemy.
+
+See https://github.com/PyCQA/pylint/issues/5679
+"""
+from other_funcs import FromClause
+
+from .nodes import roles
+
+
+class HasMemoized(object):
+    ...
+
+
+class Generative(HasMemoized):
+    ...
+
+
+class ColumnElement(
+    roles.ColumnArgumentOrKeyRole,
+    roles.BinaryElementRole,
+    roles.OrderByRole,
+    roles.ColumnsClauseRole,
+    roles.LimitOffsetRole,
+    roles.DMLColumnRole,
+    roles.DDLConstraintColumnRole,
+    roles.StatementRole,
+    Generative,
+):
+    ...
+
+
+class FunctionElement(ColumnElement, FromClause):
+    ...
+
+
+class months_between(FunctionElement):
+    def __init__(self):
+        super().__init__()

tests/testdata/python3/data/max_inferable_limit_for_classes/nodes/roles.py

@@ -0,0 +1,82 @@
+class SQLRole(object):
+    ...
+
+
+class UsesInspection(object):
+    ...
+
+
+class AllowsLambdaRole(object):
+    ...
+
+
+class ColumnArgumentRole(SQLRole):
+    ...
+
+
+class ColumnArgumentOrKeyRole(ColumnArgumentRole):
+    ...
+
+
+class ColumnListRole(SQLRole):
+    ...
+
+
+class ColumnsClauseRole(AllowsLambdaRole, UsesInspection, ColumnListRole):
+    ...
+
+
+class LimitOffsetRole(SQLRole):
+    ...
+
+
+class ByOfRole(ColumnListRole):
+    ...
+
+
+class OrderByRole(AllowsLambdaRole, ByOfRole):
+    ...
+
+
+class StructuralRole(SQLRole):
+    ...
+
+
+class ExpressionElementRole(SQLRole):
+    ...
+
+
+class BinaryElementRole(ExpressionElementRole):
+    ...
+
+
+class JoinTargetRole(AllowsLambdaRole, UsesInspection, StructuralRole):
+    ...
+
+
+class FromClauseRole(ColumnsClauseRole, JoinTargetRole):
+    ...
+
+
+class StrictFromClauseRole(FromClauseRole):
+    ...
+
+
+class AnonymizedFromClauseRole(StrictFromClauseRole):
+    ...
+
+
+class ReturnsRowsRole(SQLRole):
+    ...
+
+
+class StatementRole(SQLRole):
+    ...
+
+
+class DMLColumnRole(SQLRole):
+    ...
+
+
+class DDLConstraintColumnRole(SQLRole):
+    ...

tests/testdata/python3/data/max_inferable_limit_for_classes/other_funcs.py

@@ -0,0 +1,31 @@
+from operator import attrgetter
+
+from .nodes import roles
+
+
+class HasCacheKey(object):
+    ...
+
+
+class HasMemoized(object):
+    ...
+
+
+class MemoizedHasCacheKey(HasCacheKey, HasMemoized):
+    ...
+
+
+class ClauseElement(MemoizedHasCacheKey):
+    ...
+
+
+class ReturnsRows(roles.ReturnsRowsRole, ClauseElement):
+    ...
+
+
+class Selectable(ReturnsRows):
+    ...
+
+
+class FromClause(roles.AnonymizedFromClauseRole, Selectable):
+    c = property(attrgetter("columns"))

tests/unittest_regrtest.py

@@ -24,11 +24,13 @@
 
 import pytest
 
-from astroid import MANAGER, Instance, nodes, parse, test_utils
+from astroid import MANAGER, Instance, bases, nodes, parse, test_utils
 from astroid.builder import AstroidBuilder, extract_node
 from astroid.const import PY38_PLUS
+from astroid.context import InferenceContext
 from astroid.exceptions import InferenceError
 from astroid.raw_building import build_module
+from astroid.util import Uninferable
 
 from . import resources
 
@@ -399,5 +401,33 @@ class Another(subclass):
     parse(code)
 
 
+def test_max_inferred_for_complicated_class_hierarchy() -> None:
+    """Regression test for a crash reported in https://github.com/PyCQA/pylint/issues/5679.
+
+    The class hierarchy of 'sqlalchemy' is so intricate that it becomes uninferable with
+    the standard max_inferred of 100. We used to crash when this happened.
+    """
+    # Create module and get relevant nodes
+    module = resources.build_file(
+        str(resources.RESOURCE_PATH / "max_inferable_limit_for_classes" / "main.py")
+    )
+    init_attr_node = module.body[-1].body[0].body[0].value.func
+    init_object_node = module.body[-1].mro()[-1]["__init__"]
+    super_node = next(init_attr_node.expr.infer())
+
+    # Arbitrarily limit the max number of infered nodes per context
+    InferenceContext.max_inferred = -1
+    context = InferenceContext()
+
+    # Try to infer 'object.__init__' > because of limit is impossible
+    for inferred in bases._infer_stmts([init_object_node], context, frame=super):
+        assert inferred == Uninferable
+
+    # Reset inference limit
+    InferenceContext.max_inferred = 100
+    # Check that we don't crash on a previously uninferable node
+    assert super_node.getattr("__init__", context=context)[0] == Uninferable
+
+
 if __name__ == "__main__":
     unittest.main()