Fix exception causes all over the codebase

ChangeLog

@@ -23,6 +23,8 @@ Release Date: TBA
 
   Close PyCQA/pylint#3583
 
+* Fixed exception-chaining error messages.
+
 
 What's New in astroid 2.4.3?
 ============================

astroid/brain/brain_builtin_inference.py

@@ -165,13 +165,13 @@ def _container_generic_inference(node, context, node_type, transform):
     if not transformed:
         try:
             inferred = next(arg.infer(context=context))
-        except (InferenceError, StopIteration):
-            raise UseInferenceDefault()
+        except (InferenceError, StopIteration) as exc:
+            raise UseInferenceDefault from exc
         if inferred is util.Uninferable:
-            raise UseInferenceDefault()
+            raise UseInferenceDefault
         transformed = transform(inferred)
     if not transformed or transformed is util.Uninferable:
-        raise UseInferenceDefault()
+        raise UseInferenceDefault
     return transformed
 
 
@@ -267,8 +267,8 @@ def _get_elts(arg, context):
     is_iterable = lambda n: isinstance(n, (nodes.List, nodes.Tuple, nodes.Set))
     try:
         inferred = next(arg.infer(context))
-    except (InferenceError, NameInferenceError):
-        raise UseInferenceDefault()
+    except (InferenceError, NameInferenceError) as exc:
+        raise UseInferenceDefault from exc
     if isinstance(inferred, nodes.Dict):
         items = inferred.items
     elif is_iterable(inferred):
@@ -371,12 +371,12 @@ def infer_super(node, context=None):
     else:
         try:
             mro_pointer = next(node.args[0].infer(context=context))
-        except InferenceError:
-            raise UseInferenceDefault
+        except InferenceError as exc:
+            raise UseInferenceDefault from exc
         try:
             mro_type = next(node.args[1].infer(context=context))
-        except InferenceError:
-            raise UseInferenceDefault
+        except InferenceError as exc:
+            raise UseInferenceDefault from exc
 
     if mro_pointer is util.Uninferable or mro_type is util.Uninferable:
         # No way we could understand this.
@@ -397,8 +397,8 @@ 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:
-        raise UseInferenceDefault
+    except InferenceError as exc:
+        raise UseInferenceDefault from exc
 
     if obj is util.Uninferable or attr is util.Uninferable:
         # If one of the arguments is something we can't infer,
@@ -437,8 +437,8 @@ 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:
-                raise UseInferenceDefault
+            except InferenceError as exc:
+                raise UseInferenceDefault from exc
 
     raise UseInferenceDefault
 
@@ -505,8 +505,8 @@ def infer_property(node, context=None):
     getter = node.args[0]
     try:
         inferred = next(getter.infer(context=context))
-    except InferenceError:
-        raise UseInferenceDefault
+    except InferenceError as exc:
+        raise UseInferenceDefault from exc
 
     if not isinstance(inferred, (nodes.FunctionDef, nodes.Lambda)):
         raise UseInferenceDefault
@@ -673,12 +673,12 @@ def infer_isinstance(callnode, context=None):
         class_container = _class_or_tuple_to_container(
             class_or_tuple_node, context=context
         )
-    except InferenceError:
-        raise UseInferenceDefault
+    except InferenceError as exc:
+        raise UseInferenceDefault from exc
     try:
         isinstance_bool = helpers.object_isinstance(obj_node, class_container, context)
     except AstroidTypeError as exc:
-        raise UseInferenceDefault("TypeError: " + str(exc))
+        raise UseInferenceDefault("TypeError: " + str(exc)) from exc
     except MroError as exc:
         raise UseInferenceDefault from exc
     if isinstance_bool is util.Uninferable:

astroid/brain/brain_namedtuple_enum.py

@@ -51,8 +51,8 @@ def _infer_first(node, context):
             raise UseInferenceDefault()
         else:
             return value
-    except StopIteration:
-        raise InferenceError()
+    except StopIteration as exc:
+        raise InferenceError from exc
 
 
 def _find_func_form_arguments(node, context):
@@ -88,7 +88,7 @@ def infer_func_form(node, base_type, context=None, enum=False):
         name, names = _find_func_form_arguments(node, context)
         try:
             attributes = names.value.replace(",", " ").split()
-        except AttributeError:
+        except AttributeError as exc:
             if not enum:
                 attributes = [
                     _infer_first(const, context).value for const in names.elts
@@ -117,11 +117,11 @@ def infer_func_form(node, base_type, context=None, enum=False):
                             _infer_first(const, context).value for const in names.elts
                         ]
                 else:
-                    raise AttributeError
+                    raise AttributeError from exc
                 if not attributes:
-                    raise AttributeError
-    except (AttributeError, exceptions.InferenceError):
-        raise UseInferenceDefault()
+                    raise AttributeError from exc
+    except (AttributeError, exceptions.InferenceError) as exc:
+        raise UseInferenceDefault from exc
 
     attributes = [attr for attr in attributes if " " not in attr]
 
@@ -405,8 +405,8 @@ 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:
-        raise UseInferenceDefault
+    except InferenceError as exc:
+        raise UseInferenceDefault from exc
 
     if func.qname() != "typing.NamedTuple":
         raise UseInferenceDefault

astroid/brain/brain_random.py

@@ -47,8 +47,8 @@ def infer_random_sample(node, context=None):
 
     try:
         elts = random.sample(inferred_sequence.elts, length.value)
-    except ValueError:
-        raise astroid.UseInferenceDefault
+    except ValueError as exc:
+        raise astroid.UseInferenceDefault from exc
 
     new_node = astroid.List(
         lineno=node.lineno, col_offset=node.col_offset, parent=node.scope()

astroid/brain/brain_six.py

@@ -145,8 +145,8 @@ def _six_fail_hook(modname):
         attribute = modname[start_index:].lstrip(".").replace(".", "_")
         try:
             import_attr = module.getattr(attribute)[0]
-        except AttributeInferenceError:
-            raise AstroidBuildingError(modname=modname)
+        except AttributeInferenceError as exc:
+            raise AstroidBuildingError(modname=modname) from exc
         if isinstance(import_attr, nodes.Import):
             submodule = MANAGER.ast_from_module_name(import_attr.names[0][0])
             return submodule

astroid/decorators.py

@@ -134,9 +134,9 @@ def raise_if_nothing_inferred(func, instance, args, kwargs):
         # generator is empty
         if error.args:
             # pylint: disable=not-a-mapping
-            raise exceptions.InferenceError(**error.args[0])
+            raise exceptions.InferenceError(**error.args[0]) from error
         raise exceptions.InferenceError(
             "StopIteration raised without any error information."
-        )
+        ) from error
 
     yield from generator

astroid/protocols.py

@@ -498,8 +498,8 @@ def _infer_context_manager(self, mgr, context):
     elif isinstance(inferred, bases.Instance):
         try:
             enter = next(inferred.igetattr("__enter__", context=context))
-        except (exceptions.InferenceError, exceptions.AttributeInferenceError):
-            raise exceptions.InferenceError(node=inferred)
+        except (exceptions.InferenceError, exceptions.AttributeInferenceError) as exc:
+            raise exceptions.InferenceError(node=inferred) from exc
         if not isinstance(enter, bases.BoundMethod):
             raise exceptions.InferenceError(node=enter)
         yield from enter.infer_call_result(self, context)

astroid/scoped_nodes.py

@@ -2571,7 +2571,7 @@ def igetattr(self, name, context=None, class_context=True):
             else:
                 raise exceptions.InferenceError(
                     error.message, target=self, attribute=name, context=context
-                )
+                ) from error
 
     def has_dynamic_getattr(self, context=None):
         """Check if the class has a custom __getattr__ or __getattribute__.