Catch the StopIteration that result from PEP-479 or add default value in next

ChangeLog

@@ -16,6 +16,12 @@ Release date: TBA
 
   Closes PyCQA/pylint#4633
 
+* Fix unhandled StopIteration during inference, following the implementation
+  of PEP479 in python 3.7+
+
+  Closes PyCQA/pylint#4631
+  Closes #1080
+
 What's New in astroid 2.6.1?
 ============================
 Release date: 2021-06-29

astroid/arguments.py

@@ -101,6 +101,8 @@ def _unpack_keywords(self, keywords, context=None):
                 except InferenceError:
                     values[name] = util.Uninferable
                     continue
+                except StopIteration:
+                    continue
 
                 if not isinstance(inferred, nodes.Dict):
                     # Not something we can work with.
@@ -113,6 +115,8 @@ def _unpack_keywords(self, keywords, context=None):
                     except InferenceError:
                         values[name] = util.Uninferable
                         continue
+                    except StopIteration:
+                        continue
                     if not isinstance(dict_key, nodes.Const):
                         values[name] = util.Uninferable
                         continue
@@ -140,6 +144,8 @@ def _unpack_args(self, args, context=None):
                 except InferenceError:
                     values.append(util.Uninferable)
                     continue
+                except StopIteration:
+                    continue
 
                 if inferred is util.Uninferable:
                     values.append(util.Uninferable)

astroid/bases.py

@@ -169,8 +169,10 @@ def _infer_method_result_truth(instance, method_name, context):
             for value in meth.infer_call_result(instance, context=context):
                 if value is util.Uninferable:
                     return value
-
-                inferred = next(value.infer(context=context))
+                try:
+                    inferred = next(value.infer(context=context))
+                except StopIteration as e:
+                    raise InferenceError(context=context) from e
                 return inferred.bool_value()
         except InferenceError:
             pass
@@ -344,7 +346,7 @@ def getitem(self, index, context=None):
                 node=self,
                 context=context,
             )
-        return next(method.infer_call_result(self, new_context))
+        return next(method.infer_call_result(self, new_context), None)
 
 
 class UnboundMethod(Proxy):
@@ -434,7 +436,10 @@ def _infer_type_new_call(self, caller, context):
         from astroid import node_classes
 
         # Verify the metaclass
-        mcs = next(caller.args[0].infer(context=context))
+        try:
+            mcs = next(caller.args[0].infer(context=context))
+        except StopIteration as e:
+            raise InferenceError(context=context) from e
         if mcs.__class__.__name__ != "ClassDef":
             # Not a valid first argument.
             return None
@@ -443,7 +448,10 @@ def _infer_type_new_call(self, caller, context):
             return None
 
         # Verify the name
-        name = next(caller.args[1].infer(context=context))
+        try:
+            name = next(caller.args[1].infer(context=context))
+        except StopIteration as e:
+            raise InferenceError(context=context) from e
         if name.__class__.__name__ != "Const":
             # Not a valid name, needs to be a const.
             return None
@@ -452,24 +460,39 @@ def _infer_type_new_call(self, caller, context):
             return None
 
         # Verify the bases
-        bases = next(caller.args[2].infer(context=context))
+        try:
+            bases = next(caller.args[2].infer(context=context))
+        except StopIteration as e:
+            raise InferenceError(context=context) from e
         if bases.__class__.__name__ != "Tuple":
             # Needs to be a tuple.
             return None
-        inferred_bases = [next(elt.infer(context=context)) for elt in bases.elts]
+        try:
+            inferred_bases = [next(elt.infer(context=context)) for elt in bases.elts]
+        except StopIteration as e:
+            raise InferenceError(context=context) from e
         if any(base.__class__.__name__ != "ClassDef" for base in inferred_bases):
             # All the bases needs to be Classes
             return None
 
         # Verify the attributes.
-        attrs = next(caller.args[3].infer(context=context))
+        try:
+            attrs = next(caller.args[3].infer(context=context))
+        except StopIteration as e:
+            raise InferenceError(context=context) from e
         if attrs.__class__.__name__ != "Dict":
             # Needs to be a dictionary.
             return None
         cls_locals = collections.defaultdict(list)
         for key, value in attrs.items:
-            key = next(key.infer(context=context))
-            value = next(value.infer(context=context))
+            try:
+                key = next(key.infer(context=context))
+            except StopIteration as e:
+                raise InferenceError(context=context) from e
+            try:
+                value = next(value.infer(context=context))
+            except StopIteration as e:
+                raise InferenceError(context=context) from e
             # Ignore non string keys
             if key.__class__.__name__ == "Const" and isinstance(key.value, str):
                 cls_locals[key.value].append(value)

astroid/brain/brain_builtin_inference.py

@@ -329,7 +329,7 @@ def is_iterable(n):
 
     try:
         inferred = next(arg.infer(context))
-    except (InferenceError, NameInferenceError) as exc:
+    except (InferenceError, NameInferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
     if isinstance(inferred, nodes.Dict):
         items = inferred.items
@@ -432,11 +432,11 @@ def infer_super(node, context=None):
     else:
         try:
             mro_pointer = next(node.args[0].infer(context=context))
-        except InferenceError as exc:
+        except (InferenceError, StopIteration) as exc:
             raise UseInferenceDefault from exc
         try:
             mro_type = next(node.args[1].infer(context=context))
-        except InferenceError as exc:
+        except (InferenceError, StopIteration) as exc:
             raise UseInferenceDefault from exc
 
     if mro_pointer is util.Uninferable or mro_type is util.Uninferable:
@@ -458,7 +458,7 @@ def _infer_getattr_args(node, context):
     try:
         obj = next(node.args[0].infer(context=context))
         attr = next(node.args[1].infer(context=context))
-    except InferenceError as exc:
+    except (InferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
 
     if obj is util.Uninferable or attr is util.Uninferable:
@@ -496,7 +496,7 @@ def infer_getattr(node, context=None):
             # Try to infer the default and return it instead.
             try:
                 return next(node.args[2].infer(context=context))
-            except InferenceError as exc:
+            except (StopIteration, InferenceError) as exc:
                 raise UseInferenceDefault from exc
 
     raise UseInferenceDefault
@@ -544,7 +544,7 @@ def infer_callable(node, context=None):
     argument = node.args[0]
     try:
         inferred = next(argument.infer(context=context))
-    except InferenceError:
+    except (InferenceError, StopIteration):
         return util.Uninferable
     if inferred is util.Uninferable:
         return util.Uninferable
@@ -564,7 +564,7 @@ def infer_property(node, context=None):
     getter = node.args[0]
     try:
         inferred = next(getter.infer(context=context))
-    except InferenceError as exc:
+    except (InferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
 
     if not isinstance(inferred, (nodes.FunctionDef, nodes.Lambda)):
@@ -592,7 +592,7 @@ def infer_bool(node, context=None):
     argument = node.args[0]
     try:
         inferred = next(argument.infer(context=context))
-    except InferenceError:
+    except (InferenceError, StopIteration):
         return util.Uninferable
     if inferred is util.Uninferable:
         return util.Uninferable
@@ -682,7 +682,7 @@ def infer_issubclass(callnode, context=None):
 
     try:
         obj_type = next(obj_node.infer(context=context))
-    except InferenceError as exc:
+    except (InferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
     if not isinstance(obj_type, nodes.ClassDef):
         raise UseInferenceDefault("TypeError: arg 1 must be class")
@@ -749,13 +749,19 @@ def _class_or_tuple_to_container(node, context=None):
     # Move inferences results into container
     # to simplify later logic
     # raises InferenceError if any of the inferences fall through
-    node_infer = next(node.infer(context=context))
+    try:
+        node_infer = next(node.infer(context=context))
+    except StopIteration as e:
+        raise InferenceError(node=node, context=context) from e
     # arg2 MUST be a type or a TUPLE of types
     # for isinstance
     if isinstance(node_infer, nodes.Tuple):
-        class_container = [
-            next(node.infer(context=context)) for node in node_infer.elts
-        ]
+        try:
+            class_container = [
+                next(node.infer(context=context)) for node in node_infer.elts
+            ]
+        except StopIteration as e:
+            raise InferenceError(node=node, context=context) from e
         class_container = [
             klass_node for klass_node in class_container if klass_node is not None
         ]
@@ -865,7 +871,7 @@ def _build_dict_with_elements(elements):
     values = call.positional_arguments[0]
     try:
         inferred_values = next(values.infer(context=context))
-    except InferenceError:
+    except (InferenceError, StopIteration):
         return _build_dict_with_elements([])
     if inferred_values is util.Uninferable:
         return _build_dict_with_elements([])

astroid/brain/brain_functools.py

@@ -74,7 +74,7 @@ def _functools_partial_inference(node, context=None):
     partial_function = call.positional_arguments[0]
     try:
         inferred_wrapped_function = next(partial_function.infer(context=context))
-    except InferenceError as exc:
+    except (InferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
     if inferred_wrapped_function is Uninferable:
         raise UseInferenceDefault("Cannot infer the wrapped function")

astroid/brain/brain_multiprocessing.py

@@ -36,7 +36,7 @@ def Manager():
     try:
         context = next(node["default"].infer())
         base = next(node["base"].infer())
-    except InferenceError:
+    except (InferenceError, StopIteration):
         return module
 
     for node in (context, base):

astroid/brain/brain_namedtuple_enum.py

@@ -54,11 +54,11 @@ def _infer_first(node, context):
         raise UseInferenceDefault
     try:
         value = next(node.infer(context=context))
-        if value is util.Uninferable:
-            raise UseInferenceDefault()
-        return value
     except StopIteration as exc:
         raise InferenceError from exc
+    if value is util.Uninferable:
+        raise UseInferenceDefault()
+    return value
 
 
 def _find_func_form_arguments(node, context):
@@ -184,10 +184,15 @@ def infer_named_tuple(node, context=None):
         node, tuple_base_name, context=context
     )
     call_site = arguments.CallSite.from_call(node, context=context)
-    func = next(extract_node("import collections; collections.namedtuple").infer())
+    node = extract_node("import collections; collections.namedtuple")
+    try:
+
+        func = next(node.infer())
+    except StopIteration as e:
+        raise InferenceError(node=node) from e
     try:
         rename = next(call_site.infer_argument(func, "rename", context)).bool_value()
-    except InferenceError:
+    except (InferenceError, StopIteration):
         rename = False
 
     try:
@@ -471,7 +476,10 @@ def infer_typing_namedtuple_class(class_node, context=None):
     """
     ).format(typename=class_node.name, fields=",".join(annassigns_fields))
     node = extract_node(code)
-    generated_class_node = next(infer_named_tuple(node, context))
+    try:
+        generated_class_node = next(infer_named_tuple(node, context))
+    except StopIteration as e:
+        raise InferenceError(node=node, context=context) from e
     for method in class_node.mymethods():
         generated_class_node.locals[method.name] = [method]
 
@@ -507,7 +515,7 @@ def infer_typing_namedtuple(node, context=None):
     # so we extract the args and infer a named tuple.
     try:
         func = next(node.func.infer())
-    except InferenceError as exc:
+    except (InferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
 
     if func.qname() != "typing.NamedTuple":

astroid/brain/brain_nose.py

@@ -42,7 +42,7 @@ class Test(unittest.TestCase):
     )
     try:
         case = next(module["a"].infer())
-    except InferenceError:
+    except (InferenceError, StopIteration):
         return
     for method in case.methods():
         if method.name.startswith("assert") and "_" not in method.name:

astroid/brain/brain_six.py

@@ -189,7 +189,7 @@ def transform_six_add_metaclass(node):  # pylint: disable=inconsistent-return-st
 
         try:
             func = next(decorator.func.infer())
-        except InferenceError:
+        except (InferenceError, StopIteration):
             continue
         if func.qname() == SIX_ADD_METACLASS and decorator.args:
             metaclass = decorator.args[0]

astroid/brain/brain_typing.py

@@ -115,7 +115,7 @@ def infer_typing_typevar_or_newtype(node, context_itton=None):
     """Infer a typing.TypeVar(...) or typing.NewType(...) call"""
     try:
         func = next(node.func.infer(context=context_itton))
-    except InferenceError as exc:
+    except (InferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
 
     if func.qname() not in TYPING_TYPEVARS_QUALIFIED:
@@ -145,7 +145,7 @@ def infer_typing_attr(
     """Infer a typing.X[...] subscript"""
     try:
         value = next(node.value.infer())
-    except InferenceError as exc:
+    except (InferenceError, StopIteration) as exc:
         raise UseInferenceDefault from exc
 
     if (
@@ -269,7 +269,11 @@ def infer_typing_alias(
         or not isinstance(node.parent.targets[0], AssignName)
     ):
         return None
-    res = next(node.args[0].infer(context=ctx))
+    try:
+        res = next(node.args[0].infer(context=ctx))
+    except StopIteration as e:
+        raise InferenceError(node=node.args[0], context=context) from e
+
     assign_name = node.parent.targets[0]
 
     class_def = ClassDef(
@@ -333,7 +337,10 @@ def infer_tuple_alias(
     node: Call, ctx: context.InferenceContext = None
 ) -> typing.Iterator[ClassDef]:
     """Infer call to tuple alias as new subscriptable class typing.Tuple."""
-    res = next(node.args[0].infer(context=ctx))
+    try:
+        res = next(node.args[0].infer(context=ctx))
+    except StopIteration as e:
+        raise InferenceError(node=node.args[0], context=context) from e
     class_def = ClassDef(
         name="Tuple",
         parent=node.parent,