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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
"""Python code format's checker.
By default, try to follow Guido's style guide :
https://www.python.org/doc/essays/styleguide/
Some parts of the process_token method is based from The Tab Nanny std module.
"""
from __future__ import annotations
import sys
import tokenize
from functools import reduce
from re import Match
from typing import TYPE_CHECKING
from astroid import nodes
from pylint.checkers import BaseRawFileChecker, BaseTokenChecker
from pylint.checkers.utils import only_required_for_messages
from pylint.constants import WarningScope
from pylint.interfaces import HIGH
from pylint.typing import MessageDefinitionTuple
from pylint.utils.pragma_parser import OPTION_PO, PragmaParserError, parse_pragma
if TYPE_CHECKING:
from pylint.lint import PyLinter
if sys.version_info >= (3, 8):
from typing import Literal
else:
from typing_extensions import Literal
_KEYWORD_TOKENS = {
"assert",
"del",
"elif",
"except",
"for",
"if",
"in",
"not",
"raise",
"return",
"while",
"yield",
"with",
"=",
":=",
}
_JUNK_TOKENS = {tokenize.COMMENT, tokenize.NL}
MSGS: dict[str, MessageDefinitionTuple] = {
"C0301": (
"Line too long (%s/%s)",
"line-too-long",
"Used when a line is longer than a given number of characters.",
),
"C0302": (
"Too many lines in module (%s/%s)", # was W0302
"too-many-lines",
"Used when a module has too many lines, reducing its readability.",
),
"C0303": (
"Trailing whitespace",
"trailing-whitespace",
"Used when there is whitespace between the end of a line and the newline.",
),
"C0304": (
"Final newline missing",
"missing-final-newline",
"Used when the last line in a file is missing a newline.",
),
"C0305": (
"Trailing newlines",
"trailing-newlines",
"Used when there are trailing blank lines in a file.",
),
"W0311": (
"Bad indentation. Found %s %s, expected %s",
"bad-indentation",
"Used when an unexpected number of indentation's tabulations or "
"spaces has been found.",
),
"W0301": (
"Unnecessary semicolon", # was W0106
"unnecessary-semicolon",
'Used when a statement is ended by a semi-colon (";"), which '
"isn't necessary (that's python, not C ;).",
),
"C0321": (
"More than one statement on a single line",
"multiple-statements",
"Used when more than on statement are found on the same line.",
{"scope": WarningScope.NODE},
),
"C0325": (
"Unnecessary parens after %r keyword",
"superfluous-parens",
"Used when a single item in parentheses follows an if, for, or "
"other keyword.",
),
"C0327": (
"Mixed line endings LF and CRLF",
"mixed-line-endings",
"Used when there are mixed (LF and CRLF) newline signs in a file.",
),
"C0328": (
"Unexpected line ending format. There is '%s' while it should be '%s'.",
"unexpected-line-ending-format",
"Used when there is different newline than expected.",
),
}
def _last_token_on_line_is(tokens: TokenWrapper, line_end: int, token: str) -> bool:
return (
line_end > 0
and tokens.token(line_end - 1) == token
or line_end > 1
and tokens.token(line_end - 2) == token
and tokens.type(line_end - 1) == tokenize.COMMENT
)
class TokenWrapper:
"""A wrapper for readable access to token information."""
def __init__(self, tokens: list[tokenize.TokenInfo]) -> None:
self._tokens = tokens
def token(self, idx: int) -> str:
return self._tokens[idx][1]
def type(self, idx: int) -> int:
return self._tokens[idx][0]
def start_line(self, idx: int) -> int:
return self._tokens[idx][2][0]
def start_col(self, idx: int) -> int:
return self._tokens[idx][2][1]
def line(self, idx: int) -> str:
return self._tokens[idx][4]
class FormatChecker(BaseTokenChecker, BaseRawFileChecker):
"""Formatting checker.
Checks for :
* unauthorized constructions
* strict indentation
* line length
"""
# configuration section name
name = "format"
# messages
msgs = MSGS
# configuration options
# for available dict keys/values see the optik parser 'add_option' method
options = (
(
"max-line-length",
{
"default": 100,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of characters on a single line.",
},
),
(
"ignore-long-lines",
{
"type": "regexp",
"metavar": "<regexp>",
"default": r"^\s*(# )?<?https?://\S+>?$",
"help": (
"Regexp for a line that is allowed to be longer than the limit."
),
},
),
(
"single-line-if-stmt",
{
"default": False,
"type": "yn",
"metavar": "<y or n>",
"help": (
"Allow the body of an if to be on the same "
"line as the test if there is no else."
),
},
),
(
"single-line-class-stmt",
{
"default": False,
"type": "yn",
"metavar": "<y or n>",
"help": (
"Allow the body of a class to be on the same "
"line as the declaration if body contains "
"single statement."
),
},
),
(
"max-module-lines",
{
"default": 1000,
"type": "int",
"metavar": "<int>",
"help": "Maximum number of lines in a module.",
},
),
(
"indent-string",
{
"default": " ",
"type": "non_empty_string",
"metavar": "<string>",
"help": "String used as indentation unit. This is usually "
'" " (4 spaces) or "\\t" (1 tab).',
},
),
(
"indent-after-paren",
{
"type": "int",
"metavar": "<int>",
"default": 4,
"help": "Number of spaces of indent required inside a hanging "
"or continued line.",
},
),
(
"expected-line-ending-format",
{
"type": "choice",
"metavar": "<empty or LF or CRLF>",
"default": "",
"choices": ["", "LF", "CRLF"],
"help": (
"Expected format of line ending, "
"e.g. empty (any line ending), LF or CRLF."
),
},
),
)
def __init__(self, linter: PyLinter) -> None:
super().__init__(linter)
self._lines: dict[int, str] = {}
self._visited_lines: dict[int, Literal[1, 2]] = {}
def new_line(self, tokens: TokenWrapper, line_end: int, line_start: int) -> None:
"""A new line has been encountered, process it if necessary."""
if _last_token_on_line_is(tokens, line_end, ";"):
self.add_message("unnecessary-semicolon", line=tokens.start_line(line_end))
line_num = tokens.start_line(line_start)
line = tokens.line(line_start)
if tokens.type(line_start) not in _JUNK_TOKENS:
self._lines[line_num] = line.split("\n")[0]
self.check_lines(tokens, line_start, line, line_num)
def process_module(self, node: nodes.Module) -> None:
pass
# pylint: disable-next = too-many-return-statements, too-many-branches
def _check_keyword_parentheses(
self, tokens: list[tokenize.TokenInfo], start: int
) -> None:
"""Check that there are not unnecessary parentheses after a keyword.
Parens are unnecessary if there is exactly one balanced outer pair on a
line and contains no commas (i.e. is not a tuple).
Args:
tokens: The entire list of Tokens.
start: The position of the keyword in the token list.
"""
# If the next token is not a paren, we're fine.
if tokens[start + 1].string != "(":
return
if (
tokens[start].string == "not"
and start > 0
and tokens[start - 1].string == "is"
):
# If this is part of an `is not` expression, we have a binary operator
# so the parentheses are not necessarily redundant.
return
found_and_or = False
contains_walrus_operator = False
walrus_operator_depth = 0
contains_double_parens = 0
depth = 0
keyword_token = str(tokens[start].string)
line_num = tokens[start].start[0]
for i in range(start, len(tokens) - 1):
token = tokens[i]
# If we hit a newline, then assume any parens were for continuation.
if token.type == tokenize.NL:
return
# Since the walrus operator doesn't exist below python3.8, the tokenizer
# generates independent tokens
if (
token.string == ":=" # <-- python3.8+ path
or token.string + tokens[i + 1].string == ":="
):
contains_walrus_operator = True
walrus_operator_depth = depth
if token.string == "(":
depth += 1
if tokens[i + 1].string == "(":
contains_double_parens = 1
elif token.string == ")":
depth -= 1
if depth:
if contains_double_parens and tokens[i + 1].string == ")":
# For walrus operators in `if (not)` conditions and comprehensions
if keyword_token in {"in", "if", "not"}:
continue
return
contains_double_parens -= 1
continue
# ')' can't happen after if (foo), since it would be a syntax error.
if tokens[i + 1].string in {":", ")", "]", "}", "in"} or tokens[
i + 1
].type in {tokenize.NEWLINE, tokenize.ENDMARKER, tokenize.COMMENT}:
if contains_walrus_operator and walrus_operator_depth - 1 == depth:
return
# The empty tuple () is always accepted.
if i == start + 2:
return
if found_and_or:
return
if keyword_token == "in":
# This special case was added in https://github.com/PyCQA/pylint/pull/4948
# but it could be removed in the future. Avoid churn for now.
return
self.add_message(
"superfluous-parens", line=line_num, args=keyword_token
)
return
elif depth == 1:
# This is a tuple, which is always acceptable.
if token[1] == ",":
return
# 'and' and 'or' are the only boolean operators with lower precedence
# than 'not', so parens are only required when they are found.
if token[1] in {"and", "or"}:
found_and_or = True
# A yield inside an expression must always be in parentheses,
# quit early without error.
elif token[1] == "yield":
return
# A generator expression always has a 'for' token in it, and
# the 'for' token is only legal inside parens when it is in a
# generator expression. The parens are necessary here, so bail
# without an error.
elif token[1] == "for":
return
# A generator expression can have an 'else' token in it.
# We check the rest of the tokens to see if any problems occur after
# the 'else'.
elif token[1] == "else":
if "(" in (i.string for i in tokens[i:]):
self._check_keyword_parentheses(tokens[i:], 0)
return
def process_tokens(self, tokens: list[tokenize.TokenInfo]) -> None:
"""Process tokens and search for:
- too long lines (i.e. longer than <max_chars>)
- optionally bad construct (if given, bad_construct must be a compiled
regular expression).
"""
indents = [0]
check_equal = False
line_num = 0
self._lines = {}
self._visited_lines = {}
self._last_line_ending: str | None = None
last_blank_line_num = 0
for idx, (tok_type, string, start, _, line) in enumerate(tokens):
if start[0] != line_num:
line_num = start[0]
# A tokenizer oddity: if an indented line contains a multi-line
# docstring, the line member of the INDENT token does not contain
# the full line; therefore we check the next token on the line.
if tok_type == tokenize.INDENT:
self.new_line(TokenWrapper(tokens), idx - 1, idx + 1)
else:
self.new_line(TokenWrapper(tokens), idx - 1, idx)
if tok_type == tokenize.NEWLINE:
# a program statement, or ENDMARKER, will eventually follow,
# after some (possibly empty) run of tokens of the form
# (NL | COMMENT)* (INDENT | DEDENT+)?
# If an INDENT appears, setting check_equal is wrong, and will
# be undone when we see the INDENT.
check_equal = True
self._check_line_ending(string, line_num)
elif tok_type == tokenize.INDENT:
check_equal = False
self.check_indent_level(string, indents[-1] + 1, line_num)
indents.append(indents[-1] + 1)
elif tok_type == tokenize.DEDENT:
# there's nothing we need to check here! what's important is
# that when the run of DEDENTs ends, the indentation of the
# program statement (or ENDMARKER) that triggered the run is
# equal to what's left at the top of the indents stack
check_equal = True
if len(indents) > 1:
del indents[-1]
elif tok_type == tokenize.NL:
if not line.strip("\r\n"):
last_blank_line_num = line_num
elif tok_type not in (tokenize.COMMENT, tokenize.ENCODING):
# This is the first concrete token following a NEWLINE, so it
# must be the first token of the next program statement, or an
# ENDMARKER; the "line" argument exposes the leading white-space
# for this statement; in the case of ENDMARKER, line is an empty
# string, so will properly match the empty string with which the
# "indents" stack was seeded
if check_equal:
check_equal = False
self.check_indent_level(line, indents[-1], line_num)
if tok_type == tokenize.NUMBER and string.endswith("l"):
self.add_message("lowercase-l-suffix", line=line_num)
if string in _KEYWORD_TOKENS:
self._check_keyword_parentheses(tokens, idx)
line_num -= 1 # to be ok with "wc -l"
if line_num > self.linter.config.max_module_lines:
# Get the line where the too-many-lines (or its message id)
# was disabled or default to 1.
message_definition = self.linter.msgs_store.get_message_definitions(
"too-many-lines"
)[0]
names = (message_definition.msgid, "too-many-lines")
lineno = next(
filter(None, (self.linter._pragma_lineno.get(name) for name in names)),
1,
)
self.add_message(
"too-many-lines",
args=(line_num, self.linter.config.max_module_lines),
line=lineno,
)
# See if there are any trailing lines. Do not complain about empty
# files like __init__.py markers.
if line_num == last_blank_line_num and line_num > 0:
self.add_message("trailing-newlines", line=line_num)
def _check_line_ending(self, line_ending: str, line_num: int) -> None:
# check if line endings are mixed
if self._last_line_ending is not None:
# line_ending == "" indicates a synthetic newline added at
# the end of a file that does not, in fact, end with a
# newline.
if line_ending and line_ending != self._last_line_ending:
self.add_message("mixed-line-endings", line=line_num)
self._last_line_ending = line_ending
# check if line ending is as expected
expected = self.linter.config.expected_line_ending_format
if expected:
# reduce multiple \n\n\n\n to one \n
line_ending = reduce(lambda x, y: x + y if x != y else x, line_ending, "")
line_ending = "LF" if line_ending == "\n" else "CRLF"
if line_ending != expected:
self.add_message(
"unexpected-line-ending-format",
args=(line_ending, expected),
line=line_num,
)
@only_required_for_messages("multiple-statements")
def visit_default(self, node: nodes.NodeNG) -> None:
"""Check the node line number and check it if not yet done."""
if not node.is_statement:
return
if not node.root().pure_python:
return
prev_sibl = node.previous_sibling()
if prev_sibl is not None:
prev_line = prev_sibl.fromlineno
# The line on which a 'finally': occurs in a 'try/finally'
# is not directly represented in the AST. We infer it
# by taking the last line of the body and adding 1, which
# should be the line of finally:
elif (
isinstance(node.parent, nodes.TryFinally) and node in node.parent.finalbody
):
prev_line = node.parent.body[0].tolineno + 1
elif isinstance(node.parent, nodes.Module):
prev_line = 0
else:
prev_line = node.parent.statement(future=True).fromlineno
line = node.fromlineno
assert line, node
if prev_line == line and self._visited_lines.get(line) != 2:
self._check_multi_statement_line(node, line)
return
if line in self._visited_lines:
return
try:
tolineno = node.blockstart_tolineno
except AttributeError:
tolineno = node.tolineno
assert tolineno, node
lines: list[str] = []
for line in range(line, tolineno + 1): # noqa: B020
self._visited_lines[line] = 1
try:
lines.append(self._lines[line].rstrip())
except KeyError:
lines.append("")
def _check_multi_statement_line(self, node: nodes.NodeNG, line: int) -> None:
"""Check for lines containing multiple statements."""
# Do not warn about multiple nested context managers
# in with statements.
if isinstance(node, nodes.With):
return
# For try... except... finally..., the two nodes
# appear to be on the same line due to how the AST is built.
if isinstance(node, nodes.TryExcept) and isinstance(
node.parent, nodes.TryFinally
):
return
if (
isinstance(node.parent, nodes.If)
and not node.parent.orelse
and self.linter.config.single_line_if_stmt
):
return
if (
isinstance(node.parent, nodes.ClassDef)
and len(node.parent.body) == 1
and self.linter.config.single_line_class_stmt
):
return
# Functions stubs with ``Ellipsis`` as body are exempted.
if (
isinstance(node.parent, nodes.FunctionDef)
and isinstance(node, nodes.Expr)
and isinstance(node.value, nodes.Const)
and node.value.value is Ellipsis
):
return
self.add_message("multiple-statements", node=node)
self._visited_lines[line] = 2
def check_trailing_whitespace_ending(self, line: str, i: int) -> None:
"""Check that there is no trailing white-space."""
# exclude \f (formfeed) from the rstrip
stripped_line = line.rstrip("\t\n\r\v ")
if line[len(stripped_line) :] not in ("\n", "\r\n"):
self.add_message(
"trailing-whitespace",
line=i,
col_offset=len(stripped_line),
confidence=HIGH,
)
def check_line_length(self, line: str, i: int, checker_off: bool) -> None:
"""Check that the line length is less than the authorized value."""
max_chars = self.linter.config.max_line_length
ignore_long_line = self.linter.config.ignore_long_lines
line = line.rstrip()
if len(line) > max_chars and not ignore_long_line.search(line):
if checker_off:
self.linter.add_ignored_message("line-too-long", i)
else:
self.add_message("line-too-long", line=i, args=(len(line), max_chars))
@staticmethod
def remove_pylint_option_from_lines(options_pattern_obj: Match[str]) -> str:
"""Remove the `# pylint ...` pattern from lines."""
lines = options_pattern_obj.string
purged_lines = (
lines[: options_pattern_obj.start(1)].rstrip()
+ lines[options_pattern_obj.end(1) :]
)
return purged_lines
@staticmethod
def is_line_length_check_activated(pylint_pattern_match_object: Match[str]) -> bool:
"""Return True if the line length check is activated."""
try:
for pragma in parse_pragma(pylint_pattern_match_object.group(2)):
if pragma.action == "disable" and "line-too-long" in pragma.messages:
return False
except PragmaParserError:
# Printing useful information dealing with this error is done in the lint package
pass
return True
@staticmethod
def specific_splitlines(lines: str) -> list[str]:
"""Split lines according to universal newlines except those in a specific
sets.
"""
unsplit_ends = {
"\x0b", # synonym of \v
"\x0c", # synonym of \f
"\x1c",
"\x1d",
"\x1e",
"\x85",
"\u2028",
"\u2029",
}
res: list[str] = []
buffer = ""
for atomic_line in lines.splitlines(True):
if atomic_line[-1] not in unsplit_ends:
res.append(buffer + atomic_line)
buffer = ""
else:
buffer += atomic_line
return res
def check_lines(
self, tokens: TokenWrapper, line_start: int, lines: str, lineno: int
) -> None:
"""Check given lines for potential messages.
Check if lines have:
- a final newline
- no trailing white-space
- less than a maximum number of characters
"""
# we're first going to do a rough check whether any lines in this set
# go over the line limit. If none of them do, then we don't need to
# parse out the pylint options later on and can just assume that these
# lines are clean
# we'll also handle the line ending check here to avoid double-iteration
# unless the line lengths are suspect
max_chars = self.linter.config.max_line_length
split_lines = self.specific_splitlines(lines)
for offset, line in enumerate(split_lines):
if not line.endswith("\n"):
self.add_message("missing-final-newline", line=lineno + offset)
continue
# We don't test for trailing whitespaces in strings
# See https://github.com/PyCQA/pylint/issues/6936
# and https://github.com/PyCQA/pylint/issues/3822
if tokens.type(line_start) != tokenize.STRING:
self.check_trailing_whitespace_ending(line, lineno + offset)
# This check is purposefully simple and doesn't rstrip since this is running
# on every line you're checking it's advantageous to avoid doing a lot of work
potential_line_length_warning = any(
len(line) > max_chars for line in split_lines
)
# if there were no lines passing the max_chars config, we don't bother
# running the full line check (as we've met an even more strict condition)
if not potential_line_length_warning:
return
# Line length check may be deactivated through `pylint: disable` comment
mobj = OPTION_PO.search(lines)
checker_off = False
if mobj:
if not self.is_line_length_check_activated(mobj):
checker_off = True
# The 'pylint: disable whatever' should not be taken into account for line length count
lines = self.remove_pylint_option_from_lines(mobj)
# here we re-run specific_splitlines since we have filtered out pylint options above
for offset, line in enumerate(self.specific_splitlines(lines)):
self.check_line_length(line, lineno + offset, checker_off)
def check_indent_level(self, string: str, expected: int, line_num: int) -> None:
"""Return the indent level of the string."""
indent = self.linter.config.indent_string
if indent == "\\t": # \t is not interpreted in the configuration file
indent = "\t"
level = 0
unit_size = len(indent)
while string[:unit_size] == indent:
string = string[unit_size:]
level += 1
suppl = ""
while string and string[0] in " \t":
suppl += string[0]
string = string[1:]
if level != expected or suppl:
i_type = "spaces"
if indent[0] == "\t":
i_type = "tabs"
self.add_message(
"bad-indentation",
line=line_num,
args=(level * unit_size + len(suppl), i_type, expected * unit_size),
)
def register(linter: PyLinter) -> None:
linter.register_checker(FormatChecker(linter))
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