init

.venv/lib/python3.8/site-packages/pure_eval/my_getattr_static.py

@@ -0,0 +1,138 @@
+import types
+
+from pure_eval.utils import of_type, CannotEval
+
+_sentinel = object()
+
+
+def _static_getmro(klass):
+    return type.__dict__['__mro__'].__get__(klass)
+
+
+def _check_instance(obj, attr):
+    instance_dict = {}
+    try:
+        instance_dict = object.__getattribute__(obj, "__dict__")
+    except AttributeError:
+        pass
+    return dict.get(instance_dict, attr, _sentinel)
+
+
+def _check_class(klass, attr):
+    for entry in _static_getmro(klass):
+        if _shadowed_dict(type(entry)) is _sentinel:
+            try:
+                return entry.__dict__[attr]
+            except KeyError:
+                pass
+        else:
+            break
+    return _sentinel
+
+
+def _is_type(obj):
+    try:
+        _static_getmro(obj)
+    except TypeError:
+        return False
+    return True
+
+
+def _shadowed_dict(klass):
+    dict_attr = type.__dict__["__dict__"]
+    for entry in _static_getmro(klass):
+        try:
+            class_dict = dict_attr.__get__(entry)["__dict__"]
+        except KeyError:
+            pass
+        else:
+            if not (type(class_dict) is types.GetSetDescriptorType and
+                    class_dict.__name__ == "__dict__" and
+                    class_dict.__objclass__ is entry):
+                return class_dict
+    return _sentinel
+
+
+def getattr_static(obj, attr):
+    """Retrieve attributes without triggering dynamic lookup via the
+       descriptor protocol,  __getattr__ or __getattribute__.
+
+       Note: this function may not be able to retrieve all attributes
+       that getattr can fetch (like dynamically created attributes)
+       and may find attributes that getattr can't (like descriptors
+       that raise AttributeError). It can also return descriptor objects
+       instead of instance members in some cases. See the
+       documentation for details.
+    """
+    instance_result = _sentinel
+    if not _is_type(obj):
+        klass = type(obj)
+        dict_attr = _shadowed_dict(klass)
+        if (dict_attr is _sentinel or
+                type(dict_attr) is types.MemberDescriptorType):
+            instance_result = _check_instance(obj, attr)
+        else:
+            raise CannotEval
+    else:
+        klass = obj
+
+    klass_result = _check_class(klass, attr)
+
+    if instance_result is not _sentinel and klass_result is not _sentinel:
+        if (_check_class(type(klass_result), '__get__') is not _sentinel and
+                _check_class(type(klass_result), '__set__') is not _sentinel):
+            return _resolve_descriptor(klass_result, obj, klass)
+
+    if instance_result is not _sentinel:
+        return instance_result
+    if klass_result is not _sentinel:
+        get = _check_class(type(klass_result), '__get__')
+        if get is _sentinel:
+            return klass_result
+        else:
+            if obj is klass:
+                instance = None
+            else:
+                instance = obj
+            return _resolve_descriptor(klass_result, instance, klass)
+
+    if obj is klass:
+        # for types we check the metaclass too
+        for entry in _static_getmro(type(klass)):
+            if _shadowed_dict(type(entry)) is _sentinel:
+                try:
+                    result = entry.__dict__[attr]
+                    get = _check_class(type(result), '__get__')
+                    if get is not _sentinel:
+                        raise CannotEval
+                    return result
+                except KeyError:
+                    pass
+    raise CannotEval
+
+
+class _foo:
+    __slots__ = ['foo']
+    method = lambda: 0
+
+
+slot_descriptor = _foo.foo
+wrapper_descriptor = str.__dict__['__add__']
+method_descriptor = str.__dict__['startswith']
+user_method_descriptor = _foo.__dict__['method']
+
+safe_descriptors_raw = [
+    slot_descriptor,
+    wrapper_descriptor,
+    method_descriptor,
+    user_method_descriptor,
+]
+
+safe_descriptor_types = list(map(type, safe_descriptors_raw))
+
+
+def _resolve_descriptor(d, instance, owner):
+    try:
+        return type(of_type(d, *safe_descriptor_types)).__get__(d, instance, owner)
+    except AttributeError as e:
+        raise CannotEval from e