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Diffstat (limited to 'venv/Lib/site-packages/pylint/checkers/refactoring.py')
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diff --git a/venv/Lib/site-packages/pylint/checkers/refactoring.py b/venv/Lib/site-packages/pylint/checkers/refactoring.py new file mode 100644 index 0000000..2831343 --- /dev/null +++ b/venv/Lib/site-packages/pylint/checkers/refactoring.py @@ -0,0 +1,1510 @@ +# -*- coding: utf-8 -*- +# Copyright (c) 2016-2018 Claudiu Popa <pcmanticore@gmail.com> +# Copyright (c) 2016-2017 Łukasz Rogalski <rogalski.91@gmail.com> +# Copyright (c) 2016 Moises Lopez <moylop260@vauxoo.com> +# Copyright (c) 2016 Alexander Todorov <atodorov@otb.bg> +# Copyright (c) 2017-2018 hippo91 <guillaume.peillex@gmail.com> +# Copyright (c) 2017 Ville Skyttä <ville.skytta@iki.fi> +# Copyright (c) 2017-2018 Bryce Guinta <bryce.paul.guinta@gmail.com> +# Copyright (c) 2017 Hugo <hugovk@users.noreply.github.com> +# Copyright (c) 2017 Łukasz Sznuk <ls@rdprojekt.pl> +# Copyright (c) 2017 Alex Hearn <alex.d.hearn@gmail.com> +# Copyright (c) 2017 Antonio Ossa <aaossa@uc.cl> +# Copyright (c) 2018 Konstantin Manna <Konstantin@Manna.uno> +# Copyright (c) 2018 Konstantin <Github@pheanex.de> +# Copyright (c) 2018 Sushobhit <31987769+sushobhit27@users.noreply.github.com> +# Copyright (c) 2018 Matej Marušák <marusak.matej@gmail.com> +# Copyright (c) 2018 Ville Skyttä <ville.skytta@upcloud.com> +# Copyright (c) 2018 Mr. Senko <atodorov@mrsenko.com> + +# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html +# For details: https://github.com/PyCQA/pylint/blob/master/COPYING + +"""Looks for code which can be refactored.""" +import builtins +import collections +import itertools +import tokenize +from functools import reduce + +import astroid +from astroid import decorators + +from pylint import checkers, interfaces +from pylint import utils as lint_utils +from pylint.checkers import utils + +KNOWN_INFINITE_ITERATORS = {"itertools.count"} +BUILTIN_EXIT_FUNCS = frozenset(("quit", "exit")) + + +def _if_statement_is_always_returning(if_node, returning_node_class): + for node in if_node.body: + if isinstance(node, returning_node_class): + return True + return False + + +def _is_len_call(node): + """Checks if node is len(SOMETHING).""" + return ( + isinstance(node, astroid.Call) + and isinstance(node.func, astroid.Name) + and node.func.name == "len" + ) + + +def _is_constant_zero(node): + return isinstance(node, astroid.Const) and node.value == 0 + + +def _node_is_test_condition(node): + """ Checks if node is an if, while, assert or if expression statement.""" + return isinstance(node, (astroid.If, astroid.While, astroid.Assert, astroid.IfExp)) + + +def _is_trailing_comma(tokens, index): + """Check if the given token is a trailing comma + + :param tokens: Sequence of modules tokens + :type tokens: list[tokenize.TokenInfo] + :param int index: Index of token under check in tokens + :returns: True if the token is a comma which trails an expression + :rtype: bool + """ + token = tokens[index] + if token.exact_type != tokenize.COMMA: + return False + # Must have remaining tokens on the same line such as NEWLINE + left_tokens = itertools.islice(tokens, index + 1, None) + same_line_remaining_tokens = list( + itertools.takewhile( + lambda other_token, _token=token: other_token.start[0] == _token.start[0], + left_tokens, + ) + ) + # Note: If the newline is tokenize.NEWLINE and not tokenize.NL + # then the newline denotes the end of expression + is_last_element = all( + other_token.type in (tokenize.NEWLINE, tokenize.COMMENT) + for other_token in same_line_remaining_tokens + ) + if not same_line_remaining_tokens or not is_last_element: + return False + + def get_curline_index_start(): + """Get the index denoting the start of the current line""" + for subindex, token in enumerate(reversed(tokens[:index])): + # See Lib/tokenize.py and Lib/token.py in cpython for more info + if token.type in (tokenize.NEWLINE, tokenize.NL): + return index - subindex + return 0 + + curline_start = get_curline_index_start() + expected_tokens = {"return", "yield"} + for prevtoken in tokens[curline_start:index]: + if "=" in prevtoken.string or prevtoken.string in expected_tokens: + return True + return False + + +class RefactoringChecker(checkers.BaseTokenChecker): + """Looks for code which can be refactored + + This checker also mixes the astroid and the token approaches + in order to create knowledge about whether an "else if" node + is a true "else if" node, or an "elif" node. + """ + + __implements__ = (interfaces.ITokenChecker, interfaces.IAstroidChecker) + + name = "refactoring" + + msgs = { + "R1701": ( + "Consider merging these isinstance calls to isinstance(%s, (%s))", + "consider-merging-isinstance", + "Used when multiple consecutive isinstance calls can be merged into one.", + ), + "R1706": ( + "Consider using ternary (%s)", + "consider-using-ternary", + "Used when one of known pre-python 2.5 ternary syntax is used.", + ), + "R1709": ( + "Boolean expression may be simplified to %s", + "simplify-boolean-expression", + "Emitted when redundant pre-python 2.5 ternary syntax is used.", + ), + "R1702": ( + "Too many nested blocks (%s/%s)", + "too-many-nested-blocks", + "Used when a function or a method has too many nested " + "blocks. This makes the code less understandable and " + "maintainable.", + {"old_names": [("R0101", "old-too-many-nested-blocks")]}, + ), + "R1703": ( + "The if statement can be replaced with %s", + "simplifiable-if-statement", + "Used when an if statement can be replaced with 'bool(test)'. ", + {"old_names": [("R0102", "old-simplifiable-if-statement")]}, + ), + "R1704": ( + "Redefining argument with the local name %r", + "redefined-argument-from-local", + "Used when a local name is redefining an argument, which might " + "suggest a potential error. This is taken in account only for " + "a handful of name binding operations, such as for iteration, " + "with statement assignment and exception handler assignment.", + ), + "R1705": ( + 'Unnecessary "%s" after "return"', + "no-else-return", + "Used in order to highlight an unnecessary block of " + "code following an if containing a return statement. " + "As such, it will warn when it encounters an else " + "following a chain of ifs, all of them containing a " + "return statement.", + ), + "R1707": ( + "Disallow trailing comma tuple", + "trailing-comma-tuple", + "In Python, a tuple is actually created by the comma symbol, " + "not by the parentheses. Unfortunately, one can actually create a " + "tuple by misplacing a trailing comma, which can lead to potential " + "weird bugs in your code. You should always use parentheses " + "explicitly for creating a tuple.", + ), + "R1708": ( + "Do not raise StopIteration in generator, use return statement instead", + "stop-iteration-return", + "According to PEP479, the raise of StopIteration to end the loop of " + "a generator may lead to hard to find bugs. This PEP specify that " + "raise StopIteration has to be replaced by a simple return statement", + ), + "R1710": ( + "Either all return statements in a function should return an expression, " + "or none of them should.", + "inconsistent-return-statements", + "According to PEP8, if any return statement returns an expression, " + "any return statements where no value is returned should explicitly " + "state this as return None, and an explicit return statement " + "should be present at the end of the function (if reachable)", + ), + "R1711": ( + "Useless return at end of function or method", + "useless-return", + 'Emitted when a single "return" or "return None" statement is found ' + "at the end of function or method definition. This statement can safely be " + "removed because Python will implicitly return None", + ), + "R1712": ( + "Consider using tuple unpacking for swapping variables", + "consider-swap-variables", + "You do not have to use a temporary variable in order to " + 'swap variables. Using "tuple unpacking" to directly swap ' + "variables makes the intention more clear.", + ), + "R1713": ( + "Consider using str.join(sequence) for concatenating " + "strings from an iterable", + "consider-using-join", + "Using str.join(sequence) is faster, uses less memory " + "and increases readability compared to for-loop iteration.", + ), + "R1714": ( + 'Consider merging these comparisons with "in" to %r', + "consider-using-in", + "To check if a variable is equal to one of many values," + 'combine the values into a tuple and check if the variable is contained "in" it ' + "instead of checking for equality against each of the values." + "This is faster and less verbose.", + ), + "R1715": ( + "Consider using dict.get for getting values from a dict " + "if a key is present or a default if not", + "consider-using-get", + "Using the builtin dict.get for getting a value from a dictionary " + "if a key is present or a default if not, is simpler and considered " + "more idiomatic, although sometimes a bit slower", + ), + "R1716": ( + "Simplify chained comparison between the operands", + "chained-comparison", + "This message is emitted when pylint encounters boolean operation like" + '"a < b and b < c", suggesting instead to refactor it to "a < b < c"', + ), + "R1717": ( + "Consider using a dictionary comprehension", + "consider-using-dict-comprehension", + "Emitted when we detect the creation of a dictionary " + "using the dict() callable and a transient list. " + "Although there is nothing syntactically wrong with this code, " + "it is hard to read and can be simplified to a dict comprehension." + "Also it is faster since you don't need to create another " + "transient list", + ), + "R1718": ( + "Consider using a set comprehension", + "consider-using-set-comprehension", + "Although there is nothing syntactically wrong with this code, " + "it is hard to read and can be simplified to a set comprehension." + "Also it is faster since you don't need to create another " + "transient list", + ), + "R1719": ( + "The if expression can be replaced with %s", + "simplifiable-if-expression", + "Used when an if expression can be replaced with 'bool(test)'. ", + ), + "R1720": ( + 'Unnecessary "%s" after "raise"', + "no-else-raise", + "Used in order to highlight an unnecessary block of " + "code following an if containing a raise statement. " + "As such, it will warn when it encounters an else " + "following a chain of ifs, all of them containing a " + "raise statement.", + ), + "R1721": ( + "Unnecessary use of a comprehension", + "unnecessary-comprehension", + "Instead of using an identitiy comprehension, " + "consider using the list, dict or set constructor. " + "It is faster and simpler.", + ), + "R1722": ( + "Consider using sys.exit()", + "consider-using-sys-exit", + "Instead of using exit() or quit(), consider using the sys.exit().", + ), + "R1723": ( + 'Unnecessary "%s" after "break"', + "no-else-break", + "Used in order to highlight an unnecessary block of " + "code following an if containing a break statement. " + "As such, it will warn when it encounters an else " + "following a chain of ifs, all of them containing a " + "break statement.", + ), + "R1724": ( + 'Unnecessary "%s" after "continue"', + "no-else-continue", + "Used in order to highlight an unnecessary block of " + "code following an if containing a continue statement. " + "As such, it will warn when it encounters an else " + "following a chain of ifs, all of them containing a " + "continue statement.", + ), + } + options = ( + ( + "max-nested-blocks", + { + "default": 5, + "type": "int", + "metavar": "<int>", + "help": "Maximum number of nested blocks for function / method body", + }, + ), + ( + "never-returning-functions", + { + "default": ("sys.exit",), + "type": "csv", + "help": "Complete name of functions that never returns. When checking " + "for inconsistent-return-statements if a never returning function is " + "called then it will be considered as an explicit return statement " + "and no message will be printed.", + }, + ), + ) + + priority = 0 + + def __init__(self, linter=None): + checkers.BaseTokenChecker.__init__(self, linter) + self._return_nodes = {} + self._init() + self._never_returning_functions = None + + def _init(self): + self._nested_blocks = [] + self._elifs = [] + self._nested_blocks_msg = None + self._reported_swap_nodes = set() + + def open(self): + # do this in open since config not fully initialized in __init__ + self._never_returning_functions = set(self.config.never_returning_functions) + + @decorators.cachedproperty + def _dummy_rgx(self): + return lint_utils.get_global_option(self, "dummy-variables-rgx", default=None) + + @staticmethod + def _is_bool_const(node): + return isinstance(node.value, astroid.Const) and isinstance( + node.value.value, bool + ) + + def _is_actual_elif(self, node): + """Check if the given node is an actual elif + + This is a problem we're having with the builtin ast module, + which splits `elif` branches into a separate if statement. + Unfortunately we need to know the exact type in certain + cases. + """ + if isinstance(node.parent, astroid.If): + orelse = node.parent.orelse + # current if node must directly follow an "else" + if orelse and orelse == [node]: + if (node.lineno, node.col_offset) in self._elifs: + return True + return False + + def _check_simplifiable_if(self, node): + """Check if the given if node can be simplified. + + The if statement can be reduced to a boolean expression + in some cases. For instance, if there are two branches + and both of them return a boolean value that depends on + the result of the statement's test, then this can be reduced + to `bool(test)` without losing any functionality. + """ + + if self._is_actual_elif(node): + # Not interested in if statements with multiple branches. + return + if len(node.orelse) != 1 or len(node.body) != 1: + return + + # Check if both branches can be reduced. + first_branch = node.body[0] + else_branch = node.orelse[0] + if isinstance(first_branch, astroid.Return): + if not isinstance(else_branch, astroid.Return): + return + first_branch_is_bool = self._is_bool_const(first_branch) + else_branch_is_bool = self._is_bool_const(else_branch) + reduced_to = "'return bool(test)'" + elif isinstance(first_branch, astroid.Assign): + if not isinstance(else_branch, astroid.Assign): + return + + # Check if we assign to the same value + first_branch_targets = [ + target.name + for target in first_branch.targets + if isinstance(target, astroid.AssignName) + ] + else_branch_targets = [ + target.name + for target in else_branch.targets + if isinstance(target, astroid.AssignName) + ] + if not first_branch_targets or not else_branch_targets: + return + if sorted(first_branch_targets) != sorted(else_branch_targets): + return + + first_branch_is_bool = self._is_bool_const(first_branch) + else_branch_is_bool = self._is_bool_const(else_branch) + reduced_to = "'var = bool(test)'" + else: + return + + if not first_branch_is_bool or not else_branch_is_bool: + return + if not first_branch.value.value: + # This is a case that can't be easily simplified and + # if it can be simplified, it will usually result in a + # code that's harder to understand and comprehend. + # Let's take for instance `arg and arg <= 3`. This could theoretically be + # reduced to `not arg or arg > 3`, but the net result is that now the + # condition is harder to understand, because it requires understanding of + # an extra clause: + # * first, there is the negation of truthness with `not arg` + # * the second clause is `arg > 3`, which occurs when arg has a + # a truth value, but it implies that `arg > 3` is equivalent + # with `arg and arg > 3`, which means that the user must + # think about this assumption when evaluating `arg > 3`. + # The original form is easier to grasp. + return + + self.add_message("simplifiable-if-statement", node=node, args=(reduced_to,)) + + def process_tokens(self, tokens): + # Process tokens and look for 'if' or 'elif' + for index, token in enumerate(tokens): + token_string = token[1] + if token_string == "elif": + # AST exists by the time process_tokens is called, so + # it's safe to assume tokens[index+1] + # exists. tokens[index+1][2] is the elif's position as + # reported by CPython and PyPy, + # tokens[index][2] is the actual position and also is + # reported by IronPython. + self._elifs.extend([tokens[index][2], tokens[index + 1][2]]) + elif _is_trailing_comma(tokens, index): + if self.linter.is_message_enabled("trailing-comma-tuple"): + self.add_message("trailing-comma-tuple", line=token.start[0]) + + def leave_module(self, _): + self._init() + + @utils.check_messages("too-many-nested-blocks") + def visit_tryexcept(self, node): + self._check_nested_blocks(node) + + visit_tryfinally = visit_tryexcept + visit_while = visit_tryexcept + + def _check_redefined_argument_from_local(self, name_node): + if self._dummy_rgx and self._dummy_rgx.match(name_node.name): + return + if not name_node.lineno: + # Unknown position, maybe it is a manually built AST? + return + + scope = name_node.scope() + if not isinstance(scope, astroid.FunctionDef): + return + + for defined_argument in scope.args.nodes_of_class( + astroid.AssignName, skip_klass=(astroid.Lambda,) + ): + if defined_argument.name == name_node.name: + self.add_message( + "redefined-argument-from-local", + node=name_node, + args=(name_node.name,), + ) + + @utils.check_messages("redefined-argument-from-local", "too-many-nested-blocks") + def visit_for(self, node): + self._check_nested_blocks(node) + + for name in node.target.nodes_of_class(astroid.AssignName): + self._check_redefined_argument_from_local(name) + + @utils.check_messages("redefined-argument-from-local") + def visit_excepthandler(self, node): + if node.name and isinstance(node.name, astroid.AssignName): + self._check_redefined_argument_from_local(node.name) + + @utils.check_messages("redefined-argument-from-local") + def visit_with(self, node): + for _, names in node.items: + if not names: + continue + for name in names.nodes_of_class(astroid.AssignName): + self._check_redefined_argument_from_local(name) + + def _check_superfluous_else(self, node, msg_id, returning_node_class): + if not node.orelse: + # Not interested in if statements without else. + return + + if self._is_actual_elif(node): + # Not interested in elif nodes; only if + return + + if _if_statement_is_always_returning(node, returning_node_class): + orelse = node.orelse[0] + followed_by_elif = (orelse.lineno, orelse.col_offset) in self._elifs + self.add_message( + msg_id, node=node, args="elif" if followed_by_elif else "else" + ) + + def _check_superfluous_else_return(self, node): + return self._check_superfluous_else( + node, msg_id="no-else-return", returning_node_class=astroid.Return + ) + + def _check_superfluous_else_raise(self, node): + return self._check_superfluous_else( + node, msg_id="no-else-raise", returning_node_class=astroid.Raise + ) + + def _check_superfluous_else_break(self, node): + return self._check_superfluous_else( + node, msg_id="no-else-break", returning_node_class=astroid.Break + ) + + def _check_superfluous_else_continue(self, node): + return self._check_superfluous_else( + node, msg_id="no-else-continue", returning_node_class=astroid.Continue + ) + + def _check_consider_get(self, node): + def type_and_name_are_equal(node_a, node_b): + for _type in [astroid.Name, astroid.AssignName]: + if all(isinstance(_node, _type) for _node in [node_a, node_b]): + return node_a.name == node_b.name + if all(isinstance(_node, astroid.Const) for _node in [node_a, node_b]): + return node_a.value == node_b.value + return False + + if_block_ok = ( + isinstance(node.test, astroid.Compare) + and len(node.body) == 1 + and isinstance(node.body[0], astroid.Assign) + and isinstance(node.body[0].value, astroid.Subscript) + and type_and_name_are_equal(node.body[0].value.value, node.test.ops[0][1]) + and isinstance(node.body[0].value.slice, astroid.Index) + and type_and_name_are_equal(node.body[0].value.slice.value, node.test.left) + and len(node.body[0].targets) == 1 + and isinstance(node.body[0].targets[0], astroid.AssignName) + and isinstance(utils.safe_infer(node.test.ops[0][1]), astroid.Dict) + ) + + if if_block_ok and not node.orelse: + self.add_message("consider-using-get", node=node) + elif ( + if_block_ok + and len(node.orelse) == 1 + and isinstance(node.orelse[0], astroid.Assign) + and type_and_name_are_equal( + node.orelse[0].targets[0], node.body[0].targets[0] + ) + and len(node.orelse[0].targets) == 1 + ): + self.add_message("consider-using-get", node=node) + + @utils.check_messages( + "too-many-nested-blocks", + "simplifiable-if-statement", + "no-else-return", + "no-else-raise", + "no-else-break", + "no-else-continue", + "consider-using-get", + ) + def visit_if(self, node): + self._check_simplifiable_if(node) + self._check_nested_blocks(node) + self._check_superfluous_else_return(node) + self._check_superfluous_else_raise(node) + self._check_superfluous_else_break(node) + self._check_superfluous_else_continue(node) + self._check_consider_get(node) + + @utils.check_messages("simplifiable-if-expression") + def visit_ifexp(self, node): + self._check_simplifiable_ifexp(node) + + def _check_simplifiable_ifexp(self, node): + if not isinstance(node.body, astroid.Const) or not isinstance( + node.orelse, astroid.Const + ): + return + + if not isinstance(node.body.value, bool) or not isinstance( + node.orelse.value, bool + ): + return + + if isinstance(node.test, astroid.Compare): + test_reduced_to = "test" + else: + test_reduced_to = "bool(test)" + + if (node.body.value, node.orelse.value) == (True, False): + reduced_to = "'{}'".format(test_reduced_to) + elif (node.body.value, node.orelse.value) == (False, True): + reduced_to = "'not test'" + else: + return + + self.add_message("simplifiable-if-expression", node=node, args=(reduced_to,)) + + @utils.check_messages( + "too-many-nested-blocks", "inconsistent-return-statements", "useless-return" + ) + def leave_functiondef(self, node): + # check left-over nested blocks stack + self._emit_nested_blocks_message_if_needed(self._nested_blocks) + # new scope = reinitialize the stack of nested blocks + self._nested_blocks = [] + # check consistent return statements + self._check_consistent_returns(node) + # check for single return or return None at the end + self._check_return_at_the_end(node) + self._return_nodes[node.name] = [] + + @utils.check_messages("stop-iteration-return") + def visit_raise(self, node): + self._check_stop_iteration_inside_generator(node) + + def _check_stop_iteration_inside_generator(self, node): + """Check if an exception of type StopIteration is raised inside a generator""" + frame = node.frame() + if not isinstance(frame, astroid.FunctionDef) or not frame.is_generator(): + return + if utils.node_ignores_exception(node, StopIteration): + return + if not node.exc: + return + exc = utils.safe_infer(node.exc) + if exc is None or exc is astroid.Uninferable: + return + if self._check_exception_inherit_from_stopiteration(exc): + self.add_message("stop-iteration-return", node=node) + + @staticmethod + def _check_exception_inherit_from_stopiteration(exc): + """Return True if the exception node in argument inherit from StopIteration""" + stopiteration_qname = "{}.StopIteration".format(utils.EXCEPTIONS_MODULE) + return any(_class.qname() == stopiteration_qname for _class in exc.mro()) + + def _check_consider_using_comprehension_constructor(self, node): + if ( + isinstance(node.func, astroid.Name) + and node.args + and isinstance(node.args[0], astroid.ListComp) + ): + if node.func.name == "dict" and not isinstance( + node.args[0].elt, astroid.Call + ): + message_name = "consider-using-dict-comprehension" + self.add_message(message_name, node=node) + elif node.func.name == "set": + message_name = "consider-using-set-comprehension" + self.add_message(message_name, node=node) + + @utils.check_messages( + "stop-iteration-return", + "consider-using-dict-comprehension", + "consider-using-set-comprehension", + "consider-using-sys-exit", + ) + def visit_call(self, node): + self._check_raising_stopiteration_in_generator_next_call(node) + self._check_consider_using_comprehension_constructor(node) + self._check_quit_exit_call(node) + + @staticmethod + def _has_exit_in_scope(scope): + exit_func = scope.locals.get("exit") + return bool( + exit_func and isinstance(exit_func[0], (astroid.ImportFrom, astroid.Import)) + ) + + def _check_quit_exit_call(self, node): + + if isinstance(node.func, astroid.Name) and node.func.name in BUILTIN_EXIT_FUNCS: + # If we have `exit` imported from `sys` in the current or global scope, exempt this instance. + local_scope = node.scope() + if self._has_exit_in_scope(local_scope) or self._has_exit_in_scope( + node.root() + ): + return + self.add_message("consider-using-sys-exit", node=node) + + def _check_raising_stopiteration_in_generator_next_call(self, node): + """Check if a StopIteration exception is raised by the call to next function + + If the next value has a default value, then do not add message. + + :param node: Check to see if this Call node is a next function + :type node: :class:`astroid.node_classes.Call` + """ + + def _looks_like_infinite_iterator(param): + inferred = utils.safe_infer(param) + if inferred: + return inferred.qname() in KNOWN_INFINITE_ITERATORS + return False + + if isinstance(node.func, astroid.Attribute): + # A next() method, which is now what we want. + return + + inferred = utils.safe_infer(node.func) + if getattr(inferred, "name", "") == "next": + frame = node.frame() + # The next builtin can only have up to two + # positional arguments and no keyword arguments + has_sentinel_value = len(node.args) > 1 + if ( + isinstance(frame, astroid.FunctionDef) + and frame.is_generator() + and not has_sentinel_value + and not utils.node_ignores_exception(node, StopIteration) + and not _looks_like_infinite_iterator(node.args[0]) + ): + self.add_message("stop-iteration-return", node=node) + + def _check_nested_blocks(self, node): + """Update and check the number of nested blocks + """ + # only check block levels inside functions or methods + if not isinstance(node.scope(), astroid.FunctionDef): + return + # messages are triggered on leaving the nested block. Here we save the + # stack in case the current node isn't nested in the previous one + nested_blocks = self._nested_blocks[:] + if node.parent == node.scope(): + self._nested_blocks = [node] + else: + # go through ancestors from the most nested to the less + for ancestor_node in reversed(self._nested_blocks): + if ancestor_node == node.parent: + break + self._nested_blocks.pop() + # if the node is an elif, this should not be another nesting level + if isinstance(node, astroid.If) and self._is_actual_elif(node): + if self._nested_blocks: + self._nested_blocks.pop() + self._nested_blocks.append(node) + + # send message only once per group of nested blocks + if len(nested_blocks) > len(self._nested_blocks): + self._emit_nested_blocks_message_if_needed(nested_blocks) + + def _emit_nested_blocks_message_if_needed(self, nested_blocks): + if len(nested_blocks) > self.config.max_nested_blocks: + self.add_message( + "too-many-nested-blocks", + node=nested_blocks[0], + args=(len(nested_blocks), self.config.max_nested_blocks), + ) + + @staticmethod + def _duplicated_isinstance_types(node): + """Get the duplicated types from the underlying isinstance calls. + + :param astroid.BoolOp node: Node which should contain a bunch of isinstance calls. + :returns: Dictionary of the comparison objects from the isinstance calls, + to duplicate values from consecutive calls. + :rtype: dict + """ + duplicated_objects = set() + all_types = collections.defaultdict(set) + + for call in node.values: + if not isinstance(call, astroid.Call) or len(call.args) != 2: + continue + + inferred = utils.safe_infer(call.func) + if not inferred or not utils.is_builtin_object(inferred): + continue + + if inferred.name != "isinstance": + continue + + isinstance_object = call.args[0].as_string() + isinstance_types = call.args[1] + + if isinstance_object in all_types: + duplicated_objects.add(isinstance_object) + + if isinstance(isinstance_types, astroid.Tuple): + elems = [ + class_type.as_string() for class_type in isinstance_types.itered() + ] + else: + elems = [isinstance_types.as_string()] + all_types[isinstance_object].update(elems) + + # Remove all keys which not duplicated + return { + key: value for key, value in all_types.items() if key in duplicated_objects + } + + def _check_consider_merging_isinstance(self, node): + """Check isinstance calls which can be merged together.""" + if node.op != "or": + return + + first_args = self._duplicated_isinstance_types(node) + for duplicated_name, class_names in first_args.items(): + names = sorted(name for name in class_names) + self.add_message( + "consider-merging-isinstance", + node=node, + args=(duplicated_name, ", ".join(names)), + ) + + def _check_consider_using_in(self, node): + allowed_ops = {"or": "==", "and": "!="} + + if node.op not in allowed_ops or len(node.values) < 2: + return + + for value in node.values: + if ( + not isinstance(value, astroid.Compare) + or len(value.ops) != 1 + or value.ops[0][0] not in allowed_ops[node.op] + ): + return + for comparable in value.left, value.ops[0][1]: + if isinstance(comparable, astroid.Call): + return + + # Gather variables and values from comparisons + variables, values = [], [] + for value in node.values: + variable_set = set() + for comparable in value.left, value.ops[0][1]: + if isinstance(comparable, astroid.Name): + variable_set.add(comparable.as_string()) + values.append(comparable.as_string()) + variables.append(variable_set) + + # Look for (common-)variables that occur in all comparisons + common_variables = reduce(lambda a, b: a.intersection(b), variables) + + if not common_variables: + return + + # Gather information for the suggestion + common_variable = sorted(list(common_variables))[0] + comprehension = "in" if node.op == "or" else "not in" + values = list(collections.OrderedDict.fromkeys(values)) + values.remove(common_variable) + values_string = ", ".join(values) if len(values) != 1 else values[0] + "," + suggestion = "%s %s (%s)" % (common_variable, comprehension, values_string) + + self.add_message("consider-using-in", node=node, args=(suggestion,)) + + def _check_chained_comparison(self, node): + """Check if there is any chained comparison in the expression. + + Add a refactoring message if a boolOp contains comparison like a < b and b < c, + which can be chained as a < b < c. + + Care is taken to avoid simplifying a < b < c and b < d. + """ + if node.op != "and" or len(node.values) < 2: + return + + def _find_lower_upper_bounds(comparison_node, uses): + left_operand = comparison_node.left + for operator, right_operand in comparison_node.ops: + for operand in (left_operand, right_operand): + value = None + if isinstance(operand, astroid.Name): + value = operand.name + elif isinstance(operand, astroid.Const): + value = operand.value + + if value is None: + continue + + if operator in ("<", "<="): + if operand is left_operand: + uses[value]["lower_bound"].add(comparison_node) + elif operand is right_operand: + uses[value]["upper_bound"].add(comparison_node) + elif operator in (">", ">="): + if operand is left_operand: + uses[value]["upper_bound"].add(comparison_node) + elif operand is right_operand: + uses[value]["lower_bound"].add(comparison_node) + left_operand = right_operand + + uses = collections.defaultdict( + lambda: {"lower_bound": set(), "upper_bound": set()} + ) + for comparison_node in node.values: + if isinstance(comparison_node, astroid.Compare): + _find_lower_upper_bounds(comparison_node, uses) + + for _, bounds in uses.items(): + num_shared = len(bounds["lower_bound"].intersection(bounds["upper_bound"])) + num_lower_bounds = len(bounds["lower_bound"]) + num_upper_bounds = len(bounds["upper_bound"]) + if num_shared < num_lower_bounds and num_shared < num_upper_bounds: + self.add_message("chained-comparison", node=node) + break + + @utils.check_messages( + "consider-merging-isinstance", "consider-using-in", "chained-comparison" + ) + def visit_boolop(self, node): + self._check_consider_merging_isinstance(node) + self._check_consider_using_in(node) + self._check_chained_comparison(node) + + @staticmethod + def _is_simple_assignment(node): + return ( + isinstance(node, astroid.Assign) + and len(node.targets) == 1 + and isinstance(node.targets[0], astroid.node_classes.AssignName) + and isinstance(node.value, astroid.node_classes.Name) + ) + + def _check_swap_variables(self, node): + if not node.next_sibling() or not node.next_sibling().next_sibling(): + return + assignments = [node, node.next_sibling(), node.next_sibling().next_sibling()] + if not all(self._is_simple_assignment(node) for node in assignments): + return + if any(node in self._reported_swap_nodes for node in assignments): + return + left = [node.targets[0].name for node in assignments] + right = [node.value.name for node in assignments] + if left[0] == right[-1] and left[1:] == right[:-1]: + self._reported_swap_nodes.update(assignments) + message = "consider-swap-variables" + self.add_message(message, node=node) + + @utils.check_messages( + "simplify-boolean-expression", + "consider-using-ternary", + "consider-swap-variables", + ) + def visit_assign(self, node): + self._check_swap_variables(node) + if self._is_and_or_ternary(node.value): + cond, truth_value, false_value = self._and_or_ternary_arguments(node.value) + else: + return + + if all( + isinstance(value, astroid.Compare) for value in (truth_value, false_value) + ): + return + + inferred_truth_value = utils.safe_infer(truth_value) + if inferred_truth_value in (None, astroid.Uninferable): + truth_boolean_value = True + else: + truth_boolean_value = truth_value.bool_value() + + if truth_boolean_value is False: + message = "simplify-boolean-expression" + suggestion = false_value.as_string() + else: + message = "consider-using-ternary" + suggestion = "{truth} if {cond} else {false}".format( + truth=truth_value.as_string(), + cond=cond.as_string(), + false=false_value.as_string(), + ) + self.add_message(message, node=node, args=(suggestion,)) + + visit_return = visit_assign + + def _check_consider_using_join(self, aug_assign): + """ + We start with the augmented assignment and work our way upwards. + Names of variables for nodes if match successful: + result = '' # assign + for number in ['1', '2', '3'] # for_loop + result += number # aug_assign + """ + for_loop = aug_assign.parent + if not isinstance(for_loop, astroid.For) or len(for_loop.body) > 1: + return + assign = for_loop.previous_sibling() + if not isinstance(assign, astroid.Assign): + return + result_assign_names = { + target.name + for target in assign.targets + if isinstance(target, astroid.AssignName) + } + + is_concat_loop = ( + aug_assign.op == "+=" + and isinstance(aug_assign.target, astroid.AssignName) + and len(for_loop.body) == 1 + and aug_assign.target.name in result_assign_names + and isinstance(assign.value, astroid.Const) + and isinstance(assign.value.value, str) + and isinstance(aug_assign.value, astroid.Name) + and aug_assign.value.name == for_loop.target.name + ) + if is_concat_loop: + self.add_message("consider-using-join", node=aug_assign) + + @utils.check_messages("consider-using-join") + def visit_augassign(self, node): + self._check_consider_using_join(node) + + @utils.check_messages("unnecessary-comprehension") + def visit_comprehension(self, node): + self._check_unnecessary_comprehension(node) + + def _check_unnecessary_comprehension(self, node): + if ( + isinstance(node.parent, astroid.GeneratorExp) + or len(node.ifs) != 0 + or len(node.parent.generators) != 1 + or node.is_async + ): + return + + if ( + isinstance(node.parent, astroid.DictComp) + and isinstance(node.parent.key, astroid.Name) + and isinstance(node.parent.value, astroid.Name) + and isinstance(node.target, astroid.Tuple) + and all(isinstance(elt, astroid.AssignName) for elt in node.target.elts) + ): + expr_list = [node.parent.key.name, node.parent.value.name] + target_list = [elt.name for elt in node.target.elts] + + elif isinstance(node.parent, (astroid.ListComp, astroid.SetComp)): + expr = node.parent.elt + if isinstance(expr, astroid.Name): + expr_list = expr.name + elif isinstance(expr, astroid.Tuple): + if any(not isinstance(elt, astroid.Name) for elt in expr.elts): + return + expr_list = [elt.name for elt in expr.elts] + else: + expr_list = [] + target = node.parent.generators[0].target + target_list = ( + target.name + if isinstance(target, astroid.AssignName) + else ( + [ + elt.name + for elt in target.elts + if isinstance(elt, astroid.AssignName) + ] + if isinstance(target, astroid.Tuple) + else [] + ) + ) + else: + return + if expr_list == target_list != []: + self.add_message("unnecessary-comprehension", node=node) + + @staticmethod + def _is_and_or_ternary(node): + """ + Returns true if node is 'condition and true_value or false_value' form. + + All of: condition, true_value and false_value should not be a complex boolean expression + """ + return ( + isinstance(node, astroid.BoolOp) + and node.op == "or" + and len(node.values) == 2 + and isinstance(node.values[0], astroid.BoolOp) + and not isinstance(node.values[1], astroid.BoolOp) + and node.values[0].op == "and" + and not isinstance(node.values[0].values[1], astroid.BoolOp) + and len(node.values[0].values) == 2 + ) + + @staticmethod + def _and_or_ternary_arguments(node): + false_value = node.values[1] + condition, true_value = node.values[0].values + return condition, true_value, false_value + + def visit_functiondef(self, node): + self._return_nodes[node.name] = list( + node.nodes_of_class(astroid.Return, skip_klass=astroid.FunctionDef) + ) + + def _check_consistent_returns(self, node): + """Check that all return statements inside a function are consistent. + + Return statements are consistent if: + - all returns are explicit and if there is no implicit return; + - all returns are empty and if there is, possibly, an implicit return. + + Args: + node (astroid.FunctionDef): the function holding the return statements. + + """ + # explicit return statements are those with a not None value + explicit_returns = [ + _node for _node in self._return_nodes[node.name] if _node.value is not None + ] + if not explicit_returns: + return + if len(explicit_returns) == len( + self._return_nodes[node.name] + ) and self._is_node_return_ended(node): + return + self.add_message("inconsistent-return-statements", node=node) + + def _is_node_return_ended(self, node): + """Check if the node ends with an explicit return statement. + + Args: + node (astroid.NodeNG): node to be checked. + + Returns: + bool: True if the node ends with an explicit statement, False otherwise. + + """ + # Recursion base case + if isinstance(node, astroid.Return): + return True + if isinstance(node, astroid.Call): + try: + funcdef_node = node.func.inferred()[0] + if self._is_function_def_never_returning(funcdef_node): + return True + except astroid.InferenceError: + pass + # Avoid the check inside while loop as we don't know + # if they will be completed + if isinstance(node, astroid.While): + return True + if isinstance(node, astroid.Raise): + # a Raise statement doesn't need to end with a return statement + # but if the exception raised is handled, then the handler has to + # ends with a return statement + if not node.exc: + # Ignore bare raises + return True + if not utils.is_node_inside_try_except(node): + # If the raise statement is not inside a try/except statement + # then the exception is raised and cannot be caught. No need + # to infer it. + return True + exc = utils.safe_infer(node.exc) + if exc is None or exc is astroid.Uninferable: + return False + exc_name = exc.pytype().split(".")[-1] + handlers = utils.get_exception_handlers(node, exc_name) + handlers = list(handlers) if handlers is not None else [] + if handlers: + # among all the handlers handling the exception at least one + # must end with a return statement + return any( + self._is_node_return_ended(_handler) for _handler in handlers + ) + # if no handlers handle the exception then it's ok + return True + if isinstance(node, astroid.If): + # if statement is returning if there are exactly two return statements in its + # children : one for the body part, the other for the orelse part + # Do not check if inner function definition are return ended. + is_orelse_returning = any( + self._is_node_return_ended(_ore) + for _ore in node.orelse + if not isinstance(_ore, astroid.FunctionDef) + ) + is_if_returning = any( + self._is_node_return_ended(_ifn) + for _ifn in node.body + if not isinstance(_ifn, astroid.FunctionDef) + ) + return is_if_returning and is_orelse_returning + # recurses on the children of the node except for those which are except handler + # because one cannot be sure that the handler will really be used + return any( + self._is_node_return_ended(_child) + for _child in node.get_children() + if not isinstance(_child, astroid.ExceptHandler) + ) + + def _is_function_def_never_returning(self, node): + """Return True if the function never returns. False otherwise. + + Args: + node (astroid.FunctionDef): function definition node to be analyzed. + + Returns: + bool: True if the function never returns, False otherwise. + """ + try: + return node.qname() in self._never_returning_functions + except TypeError: + return False + + def _check_return_at_the_end(self, node): + """Check for presence of a *single* return statement at the end of a + function. "return" or "return None" are useless because None is the + default return type if they are missing. + + NOTE: produces a message only if there is a single return statement + in the function body. Otherwise _check_consistent_returns() is called! + Per its implementation and PEP8 we can have a "return None" at the end + of the function body if there are other return statements before that! + """ + if len(self._return_nodes[node.name]) > 1: + return + if len(node.body) <= 1: + return + + last = node.body[-1] + if isinstance(last, astroid.Return): + # e.g. "return" + if last.value is None: + self.add_message("useless-return", node=node) + # return None" + elif isinstance(last.value, astroid.Const) and (last.value.value is None): + self.add_message("useless-return", node=node) + + +class RecommandationChecker(checkers.BaseChecker): + __implements__ = (interfaces.IAstroidChecker,) + name = "refactoring" + msgs = { + "C0200": ( + "Consider using enumerate instead of iterating with range and len", + "consider-using-enumerate", + "Emitted when code that iterates with range and len is " + "encountered. Such code can be simplified by using the " + "enumerate builtin.", + ), + "C0201": ( + "Consider iterating the dictionary directly instead of calling .keys()", + "consider-iterating-dictionary", + "Emitted when the keys of a dictionary are iterated through the .keys() " + "method. It is enough to just iterate through the dictionary itself, as " + 'in "for key in dictionary".', + ), + } + + @staticmethod + def _is_builtin(node, function): + inferred = utils.safe_infer(node) + if not inferred: + return False + return utils.is_builtin_object(inferred) and inferred.name == function + + @utils.check_messages("consider-iterating-dictionary") + def visit_call(self, node): + if not isinstance(node.func, astroid.Attribute): + return + if node.func.attrname != "keys": + return + if not isinstance(node.parent, (astroid.For, astroid.Comprehension)): + return + + inferred = utils.safe_infer(node.func) + if not isinstance(inferred, astroid.BoundMethod) or not isinstance( + inferred.bound, astroid.Dict + ): + return + + if isinstance(node.parent, (astroid.For, astroid.Comprehension)): + self.add_message("consider-iterating-dictionary", node=node) + + @utils.check_messages("consider-using-enumerate") + def visit_for(self, node): + """Emit a convention whenever range and len are used for indexing.""" + # Verify that we have a `range([start], len(...), [stop])` call and + # that the object which is iterated is used as a subscript in the + # body of the for. + + # Is it a proper range call? + if not isinstance(node.iter, astroid.Call): + return + if not self._is_builtin(node.iter.func, "range"): + return + if len(node.iter.args) == 2 and not _is_constant_zero(node.iter.args[0]): + return + if len(node.iter.args) > 2: + return + + # Is it a proper len call? + if not isinstance(node.iter.args[-1], astroid.Call): + return + second_func = node.iter.args[-1].func + if not self._is_builtin(second_func, "len"): + return + len_args = node.iter.args[-1].args + if not len_args or len(len_args) != 1: + return + iterating_object = len_args[0] + if not isinstance(iterating_object, astroid.Name): + return + # If we're defining __iter__ on self, enumerate won't work + scope = node.scope() + if iterating_object.name == "self" and scope.name == "__iter__": + return + + # Verify that the body of the for loop uses a subscript + # with the object that was iterated. This uses some heuristics + # in order to make sure that the same object is used in the + # for body. + for child in node.body: + for subscript in child.nodes_of_class(astroid.Subscript): + if not isinstance(subscript.value, astroid.Name): + continue + if not isinstance(subscript.slice, astroid.Index): + continue + if not isinstance(subscript.slice.value, astroid.Name): + continue + if subscript.slice.value.name != node.target.name: + continue + if iterating_object.name != subscript.value.name: + continue + if subscript.value.scope() != node.scope(): + # Ignore this subscript if it's not in the same + # scope. This means that in the body of the for + # loop, another scope was created, where the same + # name for the iterating object was used. + continue + self.add_message("consider-using-enumerate", node=node) + return + + +class NotChecker(checkers.BaseChecker): + """checks for too many not in comparison expressions + + - "not not" should trigger a warning + - "not" followed by a comparison should trigger a warning + """ + + __implements__ = (interfaces.IAstroidChecker,) + msgs = { + "C0113": ( + 'Consider changing "%s" to "%s"', + "unneeded-not", + "Used when a boolean expression contains an unneeded negation.", + ) + } + name = "refactoring" + reverse_op = { + "<": ">=", + "<=": ">", + ">": "<=", + ">=": "<", + "==": "!=", + "!=": "==", + "in": "not in", + "is": "is not", + } + # sets are not ordered, so for example "not set(LEFT_VALS) <= set(RIGHT_VALS)" is + # not equivalent to "set(LEFT_VALS) > set(RIGHT_VALS)" + skipped_nodes = (astroid.Set,) + # 'builtins' py3, '__builtin__' py2 + skipped_classnames = [ + "%s.%s" % (builtins.__name__, qname) for qname in ("set", "frozenset") + ] + + @utils.check_messages("unneeded-not") + def visit_unaryop(self, node): + if node.op != "not": + return + operand = node.operand + + if isinstance(operand, astroid.UnaryOp) and operand.op == "not": + self.add_message( + "unneeded-not", + node=node, + args=(node.as_string(), operand.operand.as_string()), + ) + elif isinstance(operand, astroid.Compare): + left = operand.left + # ignore multiple comparisons + if len(operand.ops) > 1: + return + operator, right = operand.ops[0] + if operator not in self.reverse_op: + return + # Ignore __ne__ as function of __eq__ + frame = node.frame() + if frame.name == "__ne__" and operator == "==": + return + for _type in (utils.node_type(left), utils.node_type(right)): + if not _type: + return + if isinstance(_type, self.skipped_nodes): + return + if ( + isinstance(_type, astroid.Instance) + and _type.qname() in self.skipped_classnames + ): + return + suggestion = "%s %s %s" % ( + left.as_string(), + self.reverse_op[operator], + right.as_string(), + ) + self.add_message( + "unneeded-not", node=node, args=(node.as_string(), suggestion) + ) + + +class LenChecker(checkers.BaseChecker): + """Checks for incorrect usage of len() inside conditions. + Pep8 states: + For sequences, (strings, lists, tuples), use the fact that empty sequences are false. + + Yes: if not seq: + if seq: + + No: if len(seq): + if not len(seq): + + Problems detected: + * if len(sequence): + * if not len(sequence): + * elif len(sequence): + * elif not len(sequence): + * while len(sequence): + * while not len(sequence): + * assert len(sequence): + * assert not len(sequence): + """ + + __implements__ = (interfaces.IAstroidChecker,) + + # configuration section name + name = "refactoring" + msgs = { + "C1801": ( + "Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty", + "len-as-condition", + "Used when Pylint detects that len(sequence) is being used " + "without explicit comparison inside a condition to determine if a sequence is empty. " + "Instead of coercing the length to a boolean, either " + "rely on the fact that empty sequences are false or " + "compare the length against a scalar.", + ) + } + + priority = -2 + options = () + + @utils.check_messages("len-as-condition") + def visit_call(self, node): + # a len(S) call is used inside a test condition + # could be if, while, assert or if expression statement + # e.g. `if len(S):` + if _is_len_call(node): + # the len() call could also be nested together with other + # boolean operations, e.g. `if z or len(x):` + parent = node.parent + while isinstance(parent, astroid.BoolOp): + parent = parent.parent + + # we're finally out of any nested boolean operations so check if + # this len() call is part of a test condition + if not _node_is_test_condition(parent): + return + if not (node is parent.test or parent.test.parent_of(node)): + return + self.add_message("len-as-condition", node=node) + + @utils.check_messages("len-as-condition") + def visit_unaryop(self, node): + """`not len(S)` must become `not S` regardless if the parent block + is a test condition or something else (boolean expression) + e.g. `if not len(S):`""" + if ( + isinstance(node, astroid.UnaryOp) + and node.op == "not" + and _is_len_call(node.operand) + ): + self.add_message("len-as-condition", node=node) + + +def register(linter): + """Required method to auto register this checker.""" + linter.register_checker(RefactoringChecker(linter)) + linter.register_checker(NotChecker(linter)) + linter.register_checker(RecommandationChecker(linter)) + linter.register_checker(LenChecker(linter)) |