@@ -293,9 +293,8 @@ class OptionsManagerMixIn:
             msg = "No config file found, using default configuration"
         print(msg, file=sys.stderr)
 
-    @staticmethod
     def _parse_toml(
-        config_file: Union[Path, str], parser: configparser.ConfigParser
+        self, config_file: Union[Path, str], parser: configparser.ConfigParser
     ) -> None:
         """Parse and handle errors of a toml configuration file."""
         with open(config_file, encoding="utf-8") as fp:
# 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


import collections
import configparser
import contextlib
import copy
import functools
import optparse  # pylint: disable=deprecated-module
import os
import sys
from pathlib import Path
from types import ModuleType
from typing import Dict, List, Optional, TextIO, Tuple, Union

import toml

from pylint import utils
from pylint.config.man_help_formatter import _ManHelpFormatter
from pylint.config.option import Option
from pylint.config.option_parser import OptionParser


def _expand_default(self, option):
    """Patch OptionParser.expand_default with custom behaviour

    This will handle defaults to avoid overriding values in the
    configuration file.
    """
    if self.parser is None or not self.default_tag:
        return option.help
    optname = option._long_opts[0][2:]
    try:
        provider = self.parser.options_manager._all_options[optname]
    except KeyError:
        value = None
    else:
        optdict = provider.get_option_def(optname)
        optname = provider.option_attrname(optname, optdict)
        value = getattr(provider.config, optname, optdict)
        value = utils._format_option_value(optdict, value)
    if value is optparse.NO_DEFAULT or not value:
        value = self.NO_DEFAULT_VALUE
    return option.help.replace(self.default_tag, str(value))


@contextlib.contextmanager
def _patch_optparse():
    # pylint: disable = redefined-variable-type
    orig_default = optparse.HelpFormatter
    try:
        optparse.HelpFormatter.expand_default = _expand_default
        yield
    finally:
        optparse.HelpFormatter.expand_default = orig_default


class OptionsManagerMixIn:
    """Handle configuration from both a configuration file and command line options"""

    def __init__(self, usage, config_file=None):
        self.config_file = config_file
        self.reset_parsers(usage)
        # list of registered options providers
        self.options_providers = []
        # dictionary associating option name to checker
        self._all_options = collections.OrderedDict()
        self._short_options = {}
        self._nocallback_options = {}
        self._mygroups = {}
        # verbosity
        self._maxlevel = 0

    def reset_parsers(self, usage=""):
        # configuration file parser
        self.cfgfile_parser = configparser.ConfigParser(
            inline_comment_prefixes=("#", ";")
        )
        # command line parser
        self.cmdline_parser = OptionParser(Option, usage=usage)
        self.cmdline_parser.options_manager = self
        self._optik_option_attrs = set(self.cmdline_parser.option_class.ATTRS)

    def register_options_provider(self, provider, own_group=True):
        """register an options provider"""
        assert provider.priority <= 0, "provider's priority can't be >= 0"
        for i, options_provider in enumerate(self.options_providers):
            if provider.priority > options_provider.priority:
                self.options_providers.insert(i, provider)
                break
        else:
            self.options_providers.append(provider)
        non_group_spec_options = [
            option for option in provider.options if "group" not in option[1]
        ]
        groups = getattr(provider, "option_groups", ())
        if own_group and non_group_spec_options:
            self.add_option_group(
                provider.name.upper(),
                provider.__doc__,
                non_group_spec_options,
                provider,
            )
        else:
            for opt, optdict in non_group_spec_options:
                self.add_optik_option(provider, self.cmdline_parser, opt, optdict)
        for gname, gdoc in groups:
            gname = gname.upper()
            goptions = [
                option
                for option in provider.options
                if option[1].get("group", "").upper() == gname
            ]
            self.add_option_group(gname, gdoc, goptions, provider)

    def add_option_group(self, group_name, _, options, provider):
        # add option group to the command line parser
        if group_name in self._mygroups:
            group = self._mygroups[group_name]
        else:
            group = optparse.OptionGroup(
                self.cmdline_parser, title=group_name.capitalize()
            )
            self.cmdline_parser.add_option_group(group)
            group.level = provider.level
            self._mygroups[group_name] = group
            # add section to the config file
            if (
                group_name != "DEFAULT"
                and group_name not in self.cfgfile_parser._sections
            ):
                self.cfgfile_parser.add_section(group_name)
        # add provider's specific options
        for opt, optdict in options:
            self.add_optik_option(provider, group, opt, optdict)

    def add_optik_option(self, provider, optikcontainer, opt, optdict):
        args, optdict = self.optik_option(provider, opt, optdict)
        option = optikcontainer.add_option(*args, **optdict)
        self._all_options[opt] = provider
        self._maxlevel = max(self._maxlevel, option.level or 0)

    def optik_option(self, provider, opt, optdict):
        """get our personal option definition and return a suitable form for
        use with optik/optparse
        """
        optdict = copy.copy(optdict)
        if "action" in optdict:
            self._nocallback_options[provider] = opt
        else:
            optdict["action"] = "callback"
            optdict["callback"] = self.cb_set_provider_option
        # default is handled here and *must not* be given to optik if you
        # want the whole machinery to work
        if "default" in optdict:
            if (
                "help" in optdict
                and optdict.get("default") is not None
                and optdict["action"] not in ("store_true", "store_false")
            ):
                optdict["help"] += " [current: %default]"
            del optdict["default"]
        args = ["--" + str(opt)]
        if "short" in optdict:
            self._short_options[optdict["short"]] = opt
            args.append("-" + optdict["short"])
            del optdict["short"]
        # cleanup option definition dict before giving it to optik
        for key in list(optdict.keys()):
            if key not in self._optik_option_attrs:
                optdict.pop(key)
        return args, optdict

    def cb_set_provider_option(self, option, opt, value, parser):
        """optik callback for option setting"""
        if opt.startswith("--"):
            # remove -- on long option
            opt = opt[2:]
        else:
            # short option, get its long equivalent
            opt = self._short_options[opt[1:]]
        # trick since we can't set action='store_true' on options
        if value is None:
            value = 1
        self.global_set_option(opt, value)

    def global_set_option(self, opt, value):
        """set option on the correct option provider"""
        self._all_options[opt].set_option(opt, value)

    def generate_config(
        self, stream: Optional[TextIO] = None, skipsections: Tuple[str, ...] = ()
    ) -> None:
        """write a configuration file according to the current configuration
        into the given stream or stdout
        """
        options_by_section: Dict[str, List[Tuple]] = {}
        sections = []
        for provider in self.options_providers:
            for section, options in provider.options_by_section():
                if section is None:
                    section = provider.name
                if section in skipsections:
                    continue
                options = [
                    (n, d, v)
                    for (n, d, v) in options
                    if d.get("type") is not None and not d.get("deprecated")
                ]
                if not options:
                    continue
                if section not in sections:
                    sections.append(section)
                alloptions = options_by_section.setdefault(section, [])
                alloptions += options
        stream = stream or sys.stdout
        printed = False
        for section in sections:
            if printed:
                print("\n", file=stream)
            utils.format_section(
                stream, section.upper(), sorted(options_by_section[section])
            )
            printed = True

    def generate_manpage(
        self, pkginfo: ModuleType, section: int = 1, stream: TextIO = sys.stdout
    ) -> None:
        with _patch_optparse():
            formatter = _ManHelpFormatter()
            formatter.output_level = self._maxlevel
            formatter.parser = self.cmdline_parser
            print(
                formatter.format_head(self.cmdline_parser, pkginfo, section),
                file=stream,
            )
            print(self.cmdline_parser.format_option_help(formatter), file=stream)
            print(formatter.format_tail(pkginfo), file=stream)

    def load_provider_defaults(self):
        """initialize configuration using default values"""
        for provider in self.options_providers:
            provider.load_defaults()

    def read_config_file(self, config_file=None, verbose=None):
        """Read the configuration file but do not load it (i.e. dispatching
        values to each options provider)
        """
        for help_level in range(1, self._maxlevel + 1):
            opt = "-".join(["long"] * help_level) + "-help"
            if opt in self._all_options:
                break  # already processed
            help_function = functools.partial(self.helpfunc, level=help_level)
            help_msg = f"{' '.join(['more'] * help_level)} verbose help."
            optdict = {
                "action": "callback",
                "callback": help_function,
                "help": help_msg,
            }
            provider = self.options_providers[0]
            self.add_optik_option(provider, self.cmdline_parser, opt, optdict)
            provider.options += ((opt, optdict),)

        if config_file is None:
            config_file = self.config_file
        if config_file is not None:
            config_file = os.path.expandvars(os.path.expanduser(config_file))
            if not os.path.exists(config_file):
                raise OSError(f"The config file {config_file} doesn't exist!")

        use_config_file = config_file and os.path.exists(config_file)
        if use_config_file:
            self.set_current_module(config_file)
            parser = self.cfgfile_parser
            if config_file.endswith(".toml"):
                self._parse_toml(config_file, parser)
            else:
                # Use this encoding in order to strip the BOM marker, if any.
                with open(config_file, encoding="utf_8_sig") as fp:
                    parser.read_file(fp)
                # normalize sections'title
                for sect, values in list(parser._sections.items()):
                    if sect.startswith("pylint."):
                        sect = sect[len("pylint.") :]
                    if not sect.isupper() and values:
                        parser._sections[sect.upper()] = values
        if not verbose:
            return
        if use_config_file:
            msg = f"Using config file {os.path.abspath(config_file)}"
        else:
            msg = "No config file found, using default configuration"
        print(msg, file=sys.stderr)

    @staticmethod
    def _parse_toml(
        config_file: Union[Path, str], parser: configparser.ConfigParser
    ) -> None:
        """Parse and handle errors of a toml configuration file."""
        with open(config_file, encoding="utf-8") as fp:
            content = toml.load(fp)
        try:
            sections_values = content["tool"]["pylint"]
        except KeyError:
            return
        for section, values in sections_values.items():
            # TOML has rich types, convert values to
            # strings as ConfigParser expects.
            for option, value in values.items():
                if isinstance(value, bool):
                    values[option] = "yes" if value else "no"
                elif isinstance(value, (int, float)):
                    values[option] = str(value)
                elif isinstance(value, list):
                    values[option] = ",".join(value)
            parser._sections[section.upper()] = values  # type: ignore

    def load_config_file(self):
        """Dispatch values previously read from a configuration file to each
        options provider)"""
        parser = self.cfgfile_parser
        for section in parser.sections():
            for option, value in parser.items(section):
                try:
                    self.global_set_option(option, value)
                except (KeyError, optparse.OptionError):
                    continue

    def load_configuration(self, **kwargs):
        """override configuration according to given parameters"""
        return self.load_configuration_from_config(kwargs)

    def load_configuration_from_config(self, config):
        for opt, opt_value in config.items():
            opt = opt.replace("_", "-")
            provider = self._all_options[opt]
            provider.set_option(opt, opt_value)

    def load_command_line_configuration(self, args=None) -> List[str]:
        """Override configuration according to command line parameters

        return additional arguments
        """
        with _patch_optparse():
            args = sys.argv[1:] if args is None else list(args)
            (options, args) = self.cmdline_parser.parse_args(args=args)
            for provider in self._nocallback_options:
                config = provider.config
                for attr in config.__dict__.keys():
                    value = getattr(options, attr, None)
                    if value is None:
                        continue
                    setattr(config, attr, value)
            return args

    def add_help_section(self, title, description, level=0):
        """add a dummy option section for help purpose"""
        group = optparse.OptionGroup(
            self.cmdline_parser, title=title.capitalize(), description=description
        )
        group.level = level
        self._maxlevel = max(self._maxlevel, level)
        self.cmdline_parser.add_option_group(group)

    def help(self, level=0):
        """return the usage string for available options"""
        self.cmdline_parser.formatter.output_level = level
        with _patch_optparse():
            return self.cmdline_parser.format_help()

    def helpfunc(self, option, opt, val, p, level):  # pylint: disable=unused-argument
        print(self.help(level))
        sys.exit(0)

Might want to add an explanation for why we get here. Can we get the incorrect item from the ValueError message? If so we might be able to pass it as an `args`.