Fix exception causes all over the codebase

pylint/checkers/base.py

@@ -396,8 +396,8 @@ def report_by_type_stats(sect, stats, _):
     for node_type in ("module", "class", "method", "function"):
         try:
             total = stats[node_type]
-        except KeyError:
-            raise exceptions.EmptyReportError()
+        except KeyError as e:
+            raise exceptions.EmptyReportError() from e
         nice_stats[node_type] = {}
         if total != 0:
             try:

pylint/checkers/typecheck.py

@@ -536,9 +536,9 @@ def _determine_callable(callable_obj):
             try:
                 # Use the last definition of __init__.
                 callable_obj = callable_obj.local_attr("__init__")[-1]
-            except exceptions.NotFoundError:
+            except exceptions.NotFoundError as e:
                 # do nothing, covered by no-init.
-                raise ValueError
+                raise ValueError from e
         else:
             callable_obj = new
 

pylint/checkers/utils.py

@@ -533,8 +533,8 @@ def next_char(i):
 def split_format_field_names(format_string) -> Tuple[str, Iterable[Tuple[bool, str]]]:
     try:
         return _string.formatter_field_name_split(format_string)
-    except ValueError:
-        raise IncompleteFormatString()
+    except ValueError as e:
+        raise IncompleteFormatString() from e
 
 
 def collect_string_fields(format_string) -> Iterable[Optional[str]]:
@@ -566,7 +566,7 @@ def collect_string_fields(format_string) -> Iterable[Optional[str]]:
             yield ""
             yield "1"
             return
-        raise IncompleteFormatString(format_string)
+        raise IncompleteFormatString(format_string) from exc
 
 
 def parse_format_method_string(
@@ -591,8 +591,8 @@ def parse_format_method_string(
                 explicit_pos_args.add(str(keyname))
             try:
                 keyword_arguments.append((keyname, list(fielditerator)))
-            except ValueError:
-                raise IncompleteFormatString()
+            except ValueError as e:
+                raise IncompleteFormatString() from e
         else:
             implicit_pos_args_cnt += 1
     return keyword_arguments, implicit_pos_args_cnt, len(explicit_pos_args)

pylint/config/option.py

@@ -86,10 +86,10 @@ def _call_validator(opttype, optdict, option, value):
     except TypeError:
         try:
             return VALIDATORS[opttype](value)
-        except Exception:
+        except Exception as e:
             raise optparse.OptionValueError(
                 "%s value (%r) should be of type %s" % (option, value, opttype)
-            )
+            ) from e
 
 
 def _validate(value, optdict, name=""):

pylint/lint/pylinter.py

@@ -509,8 +509,8 @@ def _load_reporter(self):
         else:
             try:
                 reporter_class = self._load_reporter_class()
-            except (ImportError, AttributeError):
-                raise exceptions.InvalidReporterError(name)
+            except (ImportError, AttributeError) as e:
+                raise exceptions.InvalidReporterError(name) from e
             else:
                 self.set_reporter(reporter_class())
 

pylint/pyreverse/vcgutils.py

@@ -198,12 +198,12 @@ def _write_attributes(self, attributes_dict, **args):
         for key, value in args.items():
             try:
                 _type = attributes_dict[key]
-            except KeyError:
+            except KeyError as e:
                 raise Exception(
                     """no such attribute %s
 possible attributes are %s"""
                     % (key, attributes_dict.keys())
-                )
+                ) from e
 
             if not _type:
                 self._stream.write('%s%s:"%s"\n' % (self._indent, key, value))