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"""Functions related to finding and loading plugins."""
import configparser
import inspect
import itertools
import logging
import re
import sys
from typing import Any
from typing import Dict
from typing import FrozenSet
from typing import Generator
from typing import Iterable
from typing import List
from typing import NamedTuple
from typing import Optional
from typing import Tuple
from flake8 import utils
from flake8._compat import importlib_metadata
from flake8.exceptions import ExecutionError
from flake8.exceptions import FailedToLoadPlugin
LOG = logging.getLogger(__name__)
VALID_CODE = re.compile("^[A-Z]{1,3}[0-9]{0,3}$", re.ASCII)
FLAKE8_GROUPS = frozenset(("flake8.extension", "flake8.report"))
BANNED_PLUGINS = {
"flake8-colors": "5.0",
"flake8-per-file-ignores": "3.7",
}
class Plugin(NamedTuple):
"""A plugin before loading."""
package: str
version: str
entry_point: importlib_metadata.EntryPoint
class LoadedPlugin(NamedTuple):
"""Represents a plugin after being imported."""
plugin: Plugin
obj: Any
parameters: Dict[str, bool]
@property
def entry_name(self) -> str:
"""Return the name given in the packaging metadata."""
return self.plugin.entry_point.name
@property
def display_name(self) -> str:
"""Return the name for use in user-facing / error messages."""
return f"{self.plugin.package}[{self.entry_name}]"
class Checkers(NamedTuple):
"""Classified plugins needed for checking."""
tree: List[LoadedPlugin]
logical_line: List[LoadedPlugin]
physical_line: List[LoadedPlugin]
class Plugins(NamedTuple):
"""Classified plugins."""
checkers: Checkers
reporters: Dict[str, LoadedPlugin]
disabled: List[LoadedPlugin]
def all_plugins(self) -> Generator[LoadedPlugin, None, None]:
"""Return an iterator over all :class:`LoadedPlugin`s."""
yield from self.checkers.tree
yield from self.checkers.logical_line
yield from self.checkers.physical_line
yield from self.reporters.values()
def versions_str(self) -> str:
"""Return a user-displayed list of plugin versions."""
return ", ".join(
sorted(
{
f"{loaded.plugin.package}: {loaded.plugin.version}"
for loaded in self.all_plugins()
if loaded.plugin.package not in {"flake8", "local"}
}
)
)
class PluginOptions(NamedTuple):
"""Options related to plugin loading."""
local_plugin_paths: Tuple[str, ...]
enable_extensions: FrozenSet[str]
require_plugins: FrozenSet[str]
@classmethod
def blank(cls) -> "PluginOptions":
"""Make a blank PluginOptions, mostly used for tests."""
return cls(
local_plugin_paths=(),
enable_extensions=frozenset(),
require_plugins=frozenset(),
)
def _parse_option(
cfg: configparser.RawConfigParser,
cfg_opt_name: str,
opt: Optional[str],
) -> List[str]:
# specified on commandline: use that
if opt is not None:
return utils.parse_comma_separated_list(opt)
else:
# ideally this would reuse our config parsing framework but we need to
# parse this from preliminary options before plugins are enabled
for opt_name in (cfg_opt_name, cfg_opt_name.replace("_", "-")):
val = cfg.get("flake8", opt_name, fallback=None)
if val is not None:
return utils.parse_comma_separated_list(val)
else:
return []
def parse_plugin_options(
cfg: configparser.RawConfigParser,
cfg_dir: str,
*,
enable_extensions: Optional[str],
require_plugins: Optional[str],
) -> PluginOptions:
"""Parse plugin loading related options."""
paths_s = cfg.get("flake8:local-plugins", "paths", fallback="").strip()
paths = utils.parse_comma_separated_list(paths_s)
paths = utils.normalize_paths(paths, cfg_dir)
return PluginOptions(
local_plugin_paths=tuple(paths),
enable_extensions=frozenset(
_parse_option(cfg, "enable_extensions", enable_extensions),
),
require_plugins=frozenset(
_parse_option(cfg, "require_plugins", require_plugins),
),
)
def _flake8_plugins(
eps: Iterable[importlib_metadata.EntryPoint],
name: str,
version: str,
) -> Generator[Plugin, None, None]:
pyflakes_meta = importlib_metadata.distribution("pyflakes").metadata
pycodestyle_meta = importlib_metadata.distribution("pycodestyle").metadata
for ep in eps:
if ep.group not in FLAKE8_GROUPS:
continue
if ep.name == "F":
yield Plugin(pyflakes_meta["name"], pyflakes_meta["version"], ep)
elif ep.name in "EW":
# pycodestyle provides both `E` and `W` -- but our default select
# handles those
# ideally pycodestyle's plugin entrypoints would exactly represent
# the codes they produce...
yield Plugin(
pycodestyle_meta["name"], pycodestyle_meta["version"], ep
)
else:
yield Plugin(name, version, ep)
def _find_importlib_plugins() -> Generator[Plugin, None, None]:
# some misconfigured pythons (RHEL) have things on `sys.path` twice
seen = set()
for dist in importlib_metadata.distributions():
# assigned to prevent continual reparsing
eps = dist.entry_points
# perf: skip parsing `.metadata` (slow) if no entry points match
if not any(ep.group in FLAKE8_GROUPS for ep in eps):
continue
# assigned to prevent continual reparsing
meta = dist.metadata
if meta["name"] in seen:
continue
else:
seen.add(meta["name"])
if meta["name"] in BANNED_PLUGINS:
LOG.warning(
"%s plugin is obsolete in flake8>=%s",
meta["name"],
BANNED_PLUGINS[meta["name"]],
)
continue
elif meta["name"] == "flake8":
# special case flake8 which provides plugins for pyflakes /
# pycodestyle
yield from _flake8_plugins(eps, meta["name"], meta["version"])
continue
for ep in eps:
if ep.group in FLAKE8_GROUPS:
yield Plugin(meta["name"], meta["version"], ep)
def _find_local_plugins(
cfg: configparser.RawConfigParser,
) -> Generator[Plugin, None, None]:
for plugin_type in ("extension", "report"):
group = f"flake8.{plugin_type}"
for plugin_s in utils.parse_comma_separated_list(
cfg.get("flake8:local-plugins", plugin_type, fallback="").strip(),
regexp=utils.LOCAL_PLUGIN_LIST_RE,
):
name, _, entry_str = plugin_s.partition("=")
name, entry_str = name.strip(), entry_str.strip()
ep = importlib_metadata.EntryPoint(name, entry_str, group)
yield Plugin("local", "local", ep)
def _check_required_plugins(
plugins: List[Plugin],
expected: FrozenSet[str],
) -> None:
plugin_names = {
utils.normalize_pypi_name(plugin.package) for plugin in plugins
}
expected_names = {utils.normalize_pypi_name(name) for name in expected}
missing_plugins = expected_names - plugin_names
if missing_plugins:
raise ExecutionError(
f"required plugins were not installed!\n"
f"- installed: {', '.join(sorted(plugin_names))}\n"
f"- expected: {', '.join(sorted(expected_names))}\n"
f"- missing: {', '.join(sorted(missing_plugins))}"
)
def find_plugins(
cfg: configparser.RawConfigParser,
opts: PluginOptions,
) -> List[Plugin]:
"""Discovers all plugins (but does not load them)."""
ret = [*_find_importlib_plugins(), *_find_local_plugins(cfg)]
# for determinism, sort the list
ret.sort()
_check_required_plugins(ret, opts.require_plugins)
return ret
def _parameters_for(func: Any) -> Dict[str, bool]:
"""Return the parameters for the plugin.
This will inspect the plugin and return either the function parameters
if the plugin is a function or the parameters for ``__init__`` after
``self`` if the plugin is a class.
:returns:
A dictionary mapping the parameter name to whether or not it is
required (a.k.a., is positional only/does not have a default).
"""
is_class = not inspect.isfunction(func)
if is_class:
func = func.__init__
parameters = {
parameter.name: parameter.default is inspect.Parameter.empty
for parameter in inspect.signature(func).parameters.values()
if parameter.kind is inspect.Parameter.POSITIONAL_OR_KEYWORD
}
if is_class:
parameters.pop("self", None)
return parameters
def _load_plugin(plugin: Plugin) -> LoadedPlugin:
try:
obj = plugin.entry_point.load()
except Exception as e:
raise FailedToLoadPlugin(plugin.package, e)
if not callable(obj):
err = TypeError("expected loaded plugin to be callable")
raise FailedToLoadPlugin(plugin.package, err)
return LoadedPlugin(plugin, obj, _parameters_for(obj))
def _import_plugins(
plugins: List[Plugin],
opts: PluginOptions,
) -> List[LoadedPlugin]:
sys.path.extend(opts.local_plugin_paths)
return [_load_plugin(p) for p in plugins]
def _classify_plugins(
plugins: List[LoadedPlugin],
opts: PluginOptions,
) -> Plugins:
tree = []
logical_line = []
physical_line = []
reporters = {}
disabled = []
for loaded in plugins:
if (
getattr(loaded.obj, "off_by_default", False)
and loaded.plugin.entry_point.name not in opts.enable_extensions
):
disabled.append(loaded)
elif loaded.plugin.entry_point.group == "flake8.report":
reporters[loaded.entry_name] = loaded
elif "tree" in loaded.parameters:
tree.append(loaded)
elif "logical_line" in loaded.parameters:
logical_line.append(loaded)
elif "physical_line" in loaded.parameters:
physical_line.append(loaded)
else:
raise NotImplementedError(f"what plugin type? {loaded}")
for loaded in itertools.chain(tree, logical_line, physical_line):
if not VALID_CODE.match(loaded.entry_name):
raise ExecutionError(
f"plugin code for `{loaded.display_name}` does not match "
f"{VALID_CODE.pattern}"
)
return Plugins(
checkers=Checkers(
tree=tree,
logical_line=logical_line,
physical_line=physical_line,
),
reporters=reporters,
disabled=disabled,
)
def load_plugins(
plugins: List[Plugin],
opts: PluginOptions,
) -> Plugins:
"""Load and classify all flake8 plugins.
- first: extends ``sys.path`` with ``paths`` (to import local plugins)
- next: converts the ``Plugin``s to ``LoadedPlugins``
- finally: classifies plugins into their specific types
"""
return _classify_plugins(_import_plugins(plugins, opts), opts)