Remove side effects when accessing jedi from the interpreter.

Note that there is http://bugs.python.org/issue31184.
Fixes #925.

jedi/api/interpreter.py

@@ -8,6 +8,11 @@ from jedi.evaluate.compiled import mixed
 from jedi.evaluate.context import Context
 
 
+class NamespaceObject():
+    def __init__(self, dct):
+        self.__dict__ = dct
+
+
 class MixedModuleContext(Context):
     resets_positions = True
     type = 'mixed_module'
@@ -16,7 +21,7 @@ class MixedModuleContext(Context):
         self.evaluator = evaluator
         self._namespaces = namespaces
 
-        self._namespace_objects = [type('jedi_namespace', (), n) for n in namespaces]
+        self._namespace_objects = [NamespaceObject(n) for n in namespaces]
         self._module_context = ModuleContext(evaluator, tree_module, path=path)
         self.tree_node = tree_module
 

jedi/evaluate/compiled/__init__.py

@@ -5,6 +5,7 @@ import inspect
 import re
 import sys
 import os
+import types
 from functools import partial
 
 from jedi._compatibility import builtins as _builtins, unicode
@@ -13,6 +14,7 @@ from jedi.cache import underscore_memoization, memoize_method
 from jedi.evaluate.filters import AbstractFilter, AbstractNameDefinition, \
     ContextNameMixin
 from jedi.evaluate.context import Context, LazyKnownContext
+from jedi.evaluate.compiled.getattr_static import  getattr_static
 from . import fake
 
 
@@ -22,6 +24,23 @@ if os.path.altsep is not None:
 _path_re = re.compile('(?:\.[^{0}]+|[{0}]__init__\.py)$'.format(re.escape(_sep)))
 del _sep
 
+# Those types don't exist in typing.
+MethodDescriptorType = type(str.replace)
+WrapperDescriptorType = type(set.__iter__)
+# `object.__subclasshook__` is an already executed descriptor.
+object_class_dict = type.__dict__["__dict__"].__get__(object)
+ClassMethodDescriptorType = type(object_class_dict['__subclasshook__'])
+
+ALLOWED_DESCRIPTOR_ACCESS = (
+    types.FunctionType,
+    types.GetSetDescriptorType,
+    types.MemberDescriptorType,
+    MethodDescriptorType,
+    WrapperDescriptorType,
+    ClassMethodDescriptorType,
+    staticmethod,
+    classmethod,
+)
 
 class CheckAttribute(object):
     """Raises an AttributeError if the attribute X isn't available."""
@@ -297,16 +316,17 @@ class CompiledObjectFilter(AbstractFilter):
         name = str(name)
         obj = self._compiled_object.obj
         try:
-            getattr(obj, name)
+            attr, is_get_descriptor = getattr_static(obj, name)
-            if self._is_instance and name not in dir(obj):
-                return []
         except AttributeError:
             return []
-        except Exception:
+        else:
-            # This is a bit ugly. We're basically returning this to make
+            if is_get_descriptor \
-            # lookups possible without having the actual attribute. However
+                    and not type(attr) in ALLOWED_DESCRIPTOR_ACCESS:
-            # this makes proper completion possible.
+                # In case of descriptors that have get methods we cannot return
+                # it's value, because that would mean code execution.
                 return [EmptyCompiledName(self._evaluator, name)]
+            if self._is_instance and name not in dir(obj):
+                return []
         return [self._create_name(name)]
 
     def values(self):

jedi/evaluate/compiled/getattr_static.py

@@ -0,0 +1,110 @@
+"""
+A static version of getattr.
+This is a backport of the Python 3 code with a little bit of additional
+information returned to enable Jedi to make decisions.
+"""
+
+import types
+
+_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
+    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 _safe_hasattr(obj, name):
+    return _check_class(type(obj), name) is not _sentinel
+
+
+def _safe_is_data_descriptor(obj):
+    return (_safe_hasattr(obj, '__set__') or _safe_hasattr(obj, '__delete__'))
+
+
+def getattr_static(obj, attr, default=_sentinel):
+    """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.
+
+       Returns a tuple `(attr, is_get_descriptor)`. is_get_descripter means that
+       the attribute is a descriptor that has a `__get__` attribute.
+    """
+    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:
+        klass = obj
+
+    klass_result = _check_class(klass, attr)
+
+    if instance_result is not _sentinel and klass_result is not _sentinel:
+        if _safe_hasattr(klass_result, '__get__') \
+                and _safe_is_data_descriptor(klass_result):
+            # A get/set descriptor has priority over everything.
+            return klass_result, True
+
+    if instance_result is not _sentinel:
+        return instance_result, False
+    if klass_result is not _sentinel:
+        return klass_result, _safe_hasattr(klass_result, '__get__')
+
+    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:
+                    return entry.__dict__[attr], False
+                except KeyError:
+                    pass
+    if default is not _sentinel:
+        return default, False
+    raise AttributeError(attr)

test/test_api/test_interpreter.py

@@ -2,7 +2,6 @@
 Tests of ``jedi.api.Interpreter``.
 """
 
-from ..helpers import TestCase
 import jedi
 from jedi._compatibility import is_py33
 from jedi.evaluate.compiled import mixed
@@ -179,15 +178,20 @@ def test_getitem_side_effects():
 
 
 def test_property_error():
+    lst = []
     class Foo3():
         @property
         def bar(self):
+            lst.append(1)
             raise ValueError
 
     foo = Foo3()
     _assert_interpreter_complete('foo.bar', locals(), ['bar'])
     _assert_interpreter_complete('foo.bar.baz', locals(), [])
 
+    # There should not be side effects
+    assert lst == []
+
 
 def test_param_completion():
     def foo(bar):