Mini Shell
# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/pylint-dev/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/pylint-dev/pylint/blob/main/CONTRIBUTORS.txt
"""Check for signs of poor design."""
from __future__ import annotations
import re
from collections import defaultdict
from collections.abc import Iterator
from typing import TYPE_CHECKING
import astroid
from astroid import nodes
from pylint.checkers import BaseChecker
from pylint.checkers.utils import is_enum, only_required_for_messages
from pylint.interfaces import HIGH
from pylint.typing import MessageDefinitionTuple
if TYPE_CHECKING:
from pylint.lint import PyLinter
MSGS: dict[str, MessageDefinitionTuple] = (
{ # pylint: disable=consider-using-namedtuple-or-dataclass
"R0901": (
"Too many ancestors (%s/%s)",
"too-many-ancestors",
"Used when class has too many parent classes, try to reduce "
"this to get a simpler (and so easier to use) class.",
),
"R0902": (
"Too many instance attributes (%s/%s)",
"too-many-instance-attributes",
"Used when class has too many instance attributes, try to reduce "
"this to get a simpler (and so easier to use) class.",
),
"R0903": (
"Too few public methods (%s/%s)",
"too-few-public-methods",
"Used when class has too few public methods, so be sure it's "
"really worth it.",
),
"R0904": (
"Too many public methods (%s/%s)",
"too-many-public-methods",
"Used when class has too many public methods, try to reduce "
"this to get a simpler (and so easier to use) class.",
),
"R0911": (
"Too many return statements (%s/%s)",
"too-many-return-statements",
"Used when a function or method has too many return statement, "
"making it hard to follow.",
),
"R0912": (
"Too many branches (%s/%s)",
"too-many-branches",
"Used when a function or method has too many branches, "
"making it hard to follow.",
),
"R0913": (
"Too many arguments (%s/%s)",
"too-many-arguments",
"Used when a function or method takes too many arguments.",
),
"R0914": (
"Too many local variables (%s/%s)",
"too-many-locals",
"Used when a function or method has too many local variables.",
),
"R0915": (
"Too many statements (%s/%s)",
"too-many-statements",
"Used when a function or method has too many statements. You "
"should then split it in smaller functions / methods.",
),
"R0916": (
"Too many boolean expressions in if statement (%s/%s)",
"too-many-boolean-expressions",
"Used when an if statement contains too many boolean expressions.",
),
"R0917": (
"Too many positional arguments (%s/%s)",
"too-many-positional-arguments",
"Used when a function has too many positional arguments.",
),
}
)
SPECIAL_OBJ = re.compile("^_{2}[a-z]+_{2}$")
DATACLASSES_DECORATORS = frozenset({"dataclass", "attrs"})
DATACLASS_IMPORT = "dataclasses"
ATTRS_DECORATORS = frozenset({"define", "frozen"})
ATTRS_IMPORT = "attrs"
TYPING_NAMEDTUPLE = "typing.NamedTuple"
TYPING_TYPEDDICT = "typing.TypedDict"
TYPING_EXTENSIONS_TYPEDDICT = "typing_extensions.TypedDict"
# Set of stdlib classes to ignore when calculating number of ancestors
STDLIB_CLASSES_IGNORE_ANCESTOR = frozenset(
(
"builtins.object",
"builtins.tuple",
"builtins.dict",
"builtins.list",
"builtins.set",
"bulitins.frozenset",
"collections.ChainMap",
"collections.Counter",
"collections.OrderedDict",
"collections.UserDict",
"collections.UserList",
"collections.UserString",
"collections.defaultdict",
"collections.deque",
"collections.namedtuple",
"_collections_abc.Awaitable",
"_collections_abc.Coroutine",
"_collections_abc.AsyncIterable",
"_collections_abc.AsyncIterator",
"_collections_abc.AsyncGenerator",
"_collections_abc.Hashable",
"_collections_abc.Iterable",
"_collections_abc.Iterator",
"_collections_abc.Generator",
"_collections_abc.Reversible",
"_collections_abc.Sized",
"_collections_abc.Container",
"_collections_abc.Collection",
"_collections_abc.Set",
"_collections_abc.MutableSet",
"_collections_abc.Mapping",
"_collections_abc.MutableMapping",
"_collections_abc.MappingView",
"_collections_abc.KeysView",
"_collections_abc.ItemsView",
"_collections_abc.ValuesView",
"_collections_abc.Sequence",
"_collections_abc.MutableSequence",
"_collections_abc.ByteString",
"typing.Tuple",
"typing.List",
"typing.Dict",
"typing.Set",
"typing.FrozenSet",
"typing.Deque",
"typing.DefaultDict",
"typing.OrderedDict",
"typing.Counter",
"typing.ChainMap",
"typing.Awaitable",
"typing.Coroutine",
"typing.AsyncIterable",
"typing.AsyncIterator",
"typing.AsyncGenerator",
"typing.Iterable",
"typing.Iterator",
"typing.Generator",
"typing.Reversible",
"typing.Container",
"typing.Collection",
"typing.AbstractSet",
"typing.MutableSet",
"typing.Mapping",
"typing.MutableMapping",
"typing.Sequence",
"typing.MutableSequence",
"typing.ByteString",
"typing.MappingView",
"typing.KeysView",
"typing.ItemsView",
"typing.ValuesView",
"typing.ContextManager",
"typing.AsyncContextManager",
"typing.Hashable",
"typing.Sized",
TYPING_NAMEDTUPLE,
TYPING_TYPEDDICT,
TYPING_EXTENSIONS_TYPEDDICT,
)
)
def _is_exempt_from_public_methods(node: astroid.ClassDef) -> bool:
"""Check if a class is exempt from too-few-public-methods."""
# If it's a typing.Namedtuple, typing.TypedDict or an Enum
for ancestor in node.ancestors():
if is_enum(ancestor):
return True
if ancestor.qname() in (
TYPING_NAMEDTUPLE,
TYPING_TYPEDDICT,
TYPING_EXTENSIONS_TYPEDDICT,
):
return True
# Or if it's a dataclass
if not node.decorators:
return False
root_locals = set(node.root().locals)
for decorator in node.decorators.nodes:
if isinstance(decorator, astroid.Call):
decorator = decorator.func
if not isinstance(decorator, (astroid.Name, astroid.Attribute)):
continue
if isinstance(decorator, astroid.Name):
name = decorator.name
else:
name = decorator.attrname
if name in DATACLASSES_DECORATORS and (
root_locals.intersection(DATACLASSES_DECORATORS)
or DATACLASS_IMPORT in root_locals
):
return True
if name in ATTRS_DECORATORS and (
root_locals.intersection(ATTRS_DECORATORS) or ATTRS_IMPORT in root_locals
):
return True
return False
def _count_boolean_expressions(bool_op: nodes.BoolOp) -> int:
"""Counts the number of boolean expressions in BoolOp `bool_op` (recursive).
example: a and (b or c or (d and e)) ==> 5 boolean expressions
"""
nb_bool_expr = 0
for bool_expr in bool_op.get_children():
if isinstance(bool_expr, astroid.BoolOp):
nb_bool_expr += _count_boolean_expressions(bool_expr)
else:
nb_bool_expr += 1
return nb_bool_expr
def _count_methods_in_class(node: nodes.ClassDef) -> int:
all_methods = sum(1 for method in node.methods() if not method.name.startswith("_"))
# Special methods count towards the number of public methods,
# but don't count towards there being too many methods.
for method in node.mymethods():
if SPECIAL_OBJ.search(method.name) and method.name != "__init__":
all_methods += 1
return all_methods
def _get_parents_iter(
node: nodes.ClassDef, ignored_parents: frozenset[str]
) -> Iterator[nodes.ClassDef]:
r"""Get parents of ``node``, excluding ancestors of ``ignored_parents``.
If we have the following inheritance diagram:
F
/
D E
\/
B C
\/
A # class A(B, C): ...
And ``ignored_parents`` is ``{"E"}``, then this function will return
``{A, B, C, D}`` -- both ``E`` and its ancestors are excluded.
"""
parents: set[nodes.ClassDef] = set()
to_explore = list(node.ancestors(recurs=False))
while to_explore:
parent = to_explore.pop()
if parent.qname() in ignored_parents:
continue
if parent not in parents:
# This guard might appear to be performing the same function as
# adding the resolved parents to a set to eliminate duplicates
# (legitimate due to diamond inheritance patterns), but its
# additional purpose is to prevent cycles (not normally possible,
# but potential due to inference) and thus guarantee termination
# of the while-loop
yield parent
parents.add(parent)
to_explore.extend(parent.ancestors(recurs=False))
def _get_parents(
node: nodes.ClassDef, ignored_parents: frozenset[str]
) -> set[nodes.ClassDef]:
return set(_get_parents_iter(node, ignored_parents))
class MisdesignChecker(BaseChecker):
"""Checker of potential misdesigns.
Checks for sign of poor/misdesign:
* number of methods, attributes, local variables...
* size, complexity of functions, methods
"""
# configuration section name
name = "design"
# messages
msgs = MSGS
# configuration options
options = (
(
"max-args",
{
"default": 5,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of arguments for function / method.",
},
),
(
"max-positional-arguments",
{
"default": 5,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of positional arguments for function / method.",
},
),
(
"max-locals",
{
"default": 15,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of locals for function / method body.",
},
),
(
"max-returns",
{
"default": 6,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of return / yield for function / "
"method body.",
},
),
(
"max-branches",
{
"default": 12,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of branch for function / method body.",
},
),
(
"max-statements",
{
"default": 50,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of statements in function / method body.",
},
),
(
"max-parents",
{
"default": 7,
"type": "int",
"metavar": "<num>",
"help": "Maximum number of parents for a class (see R0901).",
},
),
(
"ignored-parents",
{
"default": (),
"type": "csv",
"metavar": "<comma separated list of class names>",
"help": "List of qualified class names to ignore when counting class parents (see R0901)",
},
),
(
"max-attributes",
{
"default": 7,
"type": "int",
"metavar": "<num>",
"help": "Maximum number of attributes for a class \
(see R0902).",
},
),
(
"min-public-methods",
{
"default": 2,
"type": "int",
"metavar": "<num>",
"help": "Minimum number of public methods for a class \
(see R0903).",
},
),
(
"max-public-methods",
{
"default": 20,
"type": "int",
"metavar": "<num>",
"help": "Maximum number of public methods for a class \
(see R0904).",
},
),
(
"max-bool-expr",
{
"default": 5,
"type": "int",
"metavar": "<num>",
"help": "Maximum number of boolean expressions in an if "
"statement (see R0916).",
},
),
(
"exclude-too-few-public-methods",
{
"default": [],
"type": "regexp_csv",
"metavar": "<pattern>[,<pattern>...]",
"help": "List of regular expressions of class ancestor names "
"to ignore when counting public methods (see R0903)",
},
),
)
def __init__(self, linter: PyLinter) -> None:
super().__init__(linter)
self._returns: list[int]
self._branches: defaultdict[nodes.LocalsDictNodeNG, int]
self._stmts: list[int]
def open(self) -> None:
"""Initialize visit variables."""
self.linter.stats.reset_node_count()
self._returns = []
self._branches = defaultdict(int)
self._stmts = []
self._exclude_too_few_public_methods = (
self.linter.config.exclude_too_few_public_methods
)
def _inc_all_stmts(self, amount: int) -> None:
for i, _ in enumerate(self._stmts):
self._stmts[i] += amount
@only_required_for_messages(
"too-many-ancestors",
"too-many-instance-attributes",
"too-few-public-methods",
"too-many-public-methods",
)
def visit_classdef(self, node: nodes.ClassDef) -> None:
"""Check size of inheritance hierarchy and number of instance attributes."""
parents = _get_parents(
node,
STDLIB_CLASSES_IGNORE_ANCESTOR.union(self.linter.config.ignored_parents),
)
nb_parents = len(parents)
if nb_parents > self.linter.config.max_parents:
self.add_message(
"too-many-ancestors",
node=node,
args=(nb_parents, self.linter.config.max_parents),
)
# Something at inference time is modifying instance_attrs to add
# properties from parent classes. Given how much we cache inference
# results, mutating instance_attrs can become a real mess. Filter
# them out here until the root cause is solved.
# https://github.com/pylint-dev/astroid/issues/2273
root = node.root()
filtered_attrs = [
k for (k, v) in node.instance_attrs.items() if v[0].root() is root
]
if len(filtered_attrs) > self.linter.config.max_attributes:
self.add_message(
"too-many-instance-attributes",
node=node,
args=(len(filtered_attrs), self.linter.config.max_attributes),
)
@only_required_for_messages("too-few-public-methods", "too-many-public-methods")
def leave_classdef(self, node: nodes.ClassDef) -> None:
"""Check number of public methods."""
my_methods = sum(
1 for method in node.mymethods() if not method.name.startswith("_")
)
# Does the class contain less than n public methods ?
# This checks only the methods defined in the current class,
# since the user might not have control over the classes
# from the ancestors. It avoids some false positives
# for classes such as unittest.TestCase, which provides
# a lot of assert methods. It doesn't make sense to warn
# when the user subclasses TestCase to add his own tests.
if my_methods > self.linter.config.max_public_methods:
self.add_message(
"too-many-public-methods",
node=node,
args=(my_methods, self.linter.config.max_public_methods),
)
# Stop here if the class is excluded via configuration.
if node.type == "class" and self._exclude_too_few_public_methods:
for ancestor in node.ancestors():
if any(
pattern.match(ancestor.qname())
for pattern in self._exclude_too_few_public_methods
):
return
# Stop here for exception, metaclass, interface classes and other
# classes for which we don't need to count the methods.
if node.type != "class" or _is_exempt_from_public_methods(node):
return
# Does the class contain more than n public methods ?
# This checks all the methods defined by ancestors and
# by the current class.
all_methods = _count_methods_in_class(node)
if all_methods < self.linter.config.min_public_methods:
self.add_message(
"too-few-public-methods",
node=node,
args=(all_methods, self.linter.config.min_public_methods),
)
@only_required_for_messages(
"too-many-return-statements",
"too-many-branches",
"too-many-arguments",
"too-many-locals",
"too-many-positional-arguments",
"too-many-statements",
"keyword-arg-before-vararg",
)
def visit_functiondef(self, node: nodes.FunctionDef) -> None:
"""Check function name, docstring, arguments, redefinition,
variable names, max locals.
"""
# init branch and returns counters
self._returns.append(0)
# check number of arguments
args = node.args.args + node.args.posonlyargs + node.args.kwonlyargs
pos_args = node.args.args + node.args.posonlyargs
ignored_argument_names = self.linter.config.ignored_argument_names
if args is not None:
ignored_args_num = 0
if ignored_argument_names:
ignored_pos_args_num = sum(
1 for arg in pos_args if ignored_argument_names.match(arg.name)
)
ignored_kwonly_args_num = sum(
1
for arg in node.args.kwonlyargs
if ignored_argument_names.match(arg.name)
)
ignored_args_num = ignored_pos_args_num + ignored_kwonly_args_num
argnum = len(args) - ignored_args_num
if argnum > self.linter.config.max_args:
self.add_message(
"too-many-arguments",
node=node,
args=(len(args), self.linter.config.max_args),
)
pos_args_count = (
len(args) - len(node.args.kwonlyargs) - ignored_pos_args_num
)
if pos_args_count > self.linter.config.max_positional_arguments:
self.add_message(
"too-many-positional-arguments",
node=node,
args=(pos_args_count, self.linter.config.max_positional_arguments),
confidence=HIGH,
)
else:
ignored_args_num = 0
# check number of local variables
locnum = len(node.locals) - ignored_args_num
# decrement number of local variables if '_' is one of them
if "_" in node.locals:
locnum -= 1
if locnum > self.linter.config.max_locals:
self.add_message(
"too-many-locals",
node=node,
args=(locnum, self.linter.config.max_locals),
)
# init new statements counter
self._stmts.append(1)
visit_asyncfunctiondef = visit_functiondef
@only_required_for_messages(
"too-many-return-statements",
"too-many-branches",
"too-many-arguments",
"too-many-locals",
"too-many-statements",
)
def leave_functiondef(self, node: nodes.FunctionDef) -> None:
"""Most of the work is done here on close:
checks for max returns, branch, return in __init__.
"""
returns = self._returns.pop()
if returns > self.linter.config.max_returns:
self.add_message(
"too-many-return-statements",
node=node,
args=(returns, self.linter.config.max_returns),
)
branches = self._branches[node]
if branches > self.linter.config.max_branches:
self.add_message(
"too-many-branches",
node=node,
args=(branches, self.linter.config.max_branches),
)
# check number of statements
stmts = self._stmts.pop()
if stmts > self.linter.config.max_statements:
self.add_message(
"too-many-statements",
node=node,
args=(stmts, self.linter.config.max_statements),
)
leave_asyncfunctiondef = leave_functiondef
def visit_return(self, _: nodes.Return) -> None:
"""Count number of returns."""
if not self._returns:
return # return outside function, reported by the base checker
self._returns[-1] += 1
def visit_default(self, node: nodes.NodeNG) -> None:
"""Default visit method -> increments the statements counter if
necessary.
"""
if node.is_statement:
self._inc_all_stmts(1)
def visit_try(self, node: nodes.Try) -> None:
"""Increments the branches counter."""
branches = len(node.handlers)
if node.orelse:
branches += 1
if node.finalbody:
branches += 1
self._inc_branch(node, branches)
self._inc_all_stmts(branches)
@only_required_for_messages("too-many-boolean-expressions", "too-many-branches")
def visit_if(self, node: nodes.If) -> None:
"""Increments the branches counter and checks boolean expressions."""
self._check_boolean_expressions(node)
branches = 1
# don't double count If nodes coming from some 'elif'
if node.orelse and (
len(node.orelse) > 1 or not isinstance(node.orelse[0], astroid.If)
):
branches += 1
self._inc_branch(node, branches)
self._inc_all_stmts(branches)
def _check_boolean_expressions(self, node: nodes.If) -> None:
"""Go through "if" node `node` and count its boolean expressions
if the 'if' node test is a BoolOp node.
"""
condition = node.test
if not isinstance(condition, astroid.BoolOp):
return
nb_bool_expr = _count_boolean_expressions(condition)
if nb_bool_expr > self.linter.config.max_bool_expr:
self.add_message(
"too-many-boolean-expressions",
node=condition,
args=(nb_bool_expr, self.linter.config.max_bool_expr),
)
def visit_while(self, node: nodes.While) -> None:
"""Increments the branches counter."""
branches = 1
if node.orelse:
branches += 1
self._inc_branch(node, branches)
visit_for = visit_while
def _inc_branch(self, node: nodes.NodeNG, branchesnum: int = 1) -> None:
"""Increments the branches counter."""
self._branches[node.scope()] += branchesnum
def register(linter: PyLinter) -> None:
linter.register_checker(MisdesignChecker(linter))
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