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design_analysis.py
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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html # For details: https://github.com/PyCQA/pylint/blob/main/LICENSE # Copyright (c) https://github.com/PyCQA/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.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.", ), } SPECIAL_OBJ = re.compile("^_{2}[a-z]+_{2}$") DATACLASSES_DECORATORS = frozenset({"dataclass", "attrs"}) DATACLASS_IMPORT = "dataclasses" TYPING_NAMEDTUPLE = "typing.NamedTuple" TYPING_TYPEDDICT = "typing.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", ) ) 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): 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 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-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), ) if len(node.instance_attrs) > self.linter.config.max_attributes: self.add_message( "too-many-instance-attributes", node=node, args=(len(node.instance_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-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 ignored_argument_names = self.linter.config.ignored_argument_names if args is not None: ignored_args_num = 0 if ignored_argument_names: ignored_args_num = sum( 1 for arg in args if ignored_argument_names.match(arg.name) ) 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), ) 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_tryexcept(self, node: nodes.TryExcept) -> None: """Increments the branches counter.""" branches = len(node.handlers) if node.orelse: branches += 1 self._inc_branch(node, branches) self._inc_all_stmts(branches) def visit_tryfinally(self, node: nodes.TryFinally) -> None: """Increments the branches counter.""" self._inc_branch(node, 2) self._inc_all_stmts(2) @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))