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bpo-42382: In importlib.metadata, EntryPoint objects now expose dist #23758

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Dec 31, 2020
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bpo-42382: In importlib.metadata, EntryPoint objects now expose dist #23758

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bpo-42382: In importlib.metadata, `EntryPoint` objects now expose a `…
jaraco Dec 14, 2020
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Add blurb
jaraco Dec 14, 2020
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Remove latent footnote.
jaraco Dec 17, 2020
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11 changes: 3 additions & 8 deletions Doc/library/importlib.metadata.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -115,8 +115,9 @@ Every distribution includes some metadata, which you can extract using the

>>> wheel_metadata = metadata('wheel') # doctest: +SKIP

The keys of the returned data structure [#f1]_ name the metadata keywords, and
their values are returned unparsed from the distribution metadata::
The keys of the returned data structure, a ``PackageMetadata``,
name the metadata keywords, and
the values are returned unparsed from the distribution metadata::

>>> wheel_metadata['Requires-Python'] # doctest: +SKIP
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'
Expand Down Expand Up @@ -259,9 +260,3 @@ a custom finder, return instances of this derived ``Distribution`` in the


.. rubric:: Footnotes

.. [#f1] Technically, the returned distribution metadata object is an
:class:`email.message.EmailMessage`
instance, but this is an implementation detail, and not part of the
stable API. You should only use dictionary-like methods and syntax
to access the metadata contents.
185 changes: 119 additions & 66 deletions Lib/importlib/metadata.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@
import io
import os
import re
import abc
Expand All @@ -18,6 +17,7 @@
from importlib import import_module
from importlib.abc import MetaPathFinder
from itertools import starmap
from typing import Any, List, Optional, Protocol, TypeVar, Union


__all__ = [
Expand All @@ -31,7 +31,7 @@
'metadata',
'requires',
'version',
]
]


class PackageNotFoundError(ModuleNotFoundError):
Expand All @@ -43,7 +43,7 @@ def __str__(self):

@property
def name(self):
name, = self.args
(name,) = self.args
return name


Expand All @@ -60,7 +60,7 @@ class EntryPoint(
r'(?P<module>[\w.]+)\s*'
r'(:\s*(?P<attr>[\w.]+))?\s*'
r'(?P<extras>\[.*\])?\s*$'
)
)
"""
A regular expression describing the syntax for an entry point,
which might look like:
Expand All @@ -77,6 +77,8 @@ class EntryPoint(
following the attr, and following any extras.
"""

dist: Optional['Distribution'] = None

def load(self):
"""Load the entry point from its definition. If only a module
is indicated by the value, return that module. Otherwise,
Expand Down Expand Up @@ -104,23 +106,27 @@ def extras(self):

@classmethod
def _from_config(cls, config):
return [
return (
cls(name, value, group)
for group in config.sections()
for name, value in config.items(group)
]
)

@classmethod
def _from_text(cls, text):
config = ConfigParser(delimiters='=')
# case sensitive: https://stackoverflow.com/q/1611799/812183
config.optionxform = str
try:
config.read_string(text)
except AttributeError: # pragma: nocover
# Python 2 has no read_string
config.readfp(io.StringIO(text))
return EntryPoint._from_config(config)
config.read_string(text)
return cls._from_config(config)

@classmethod
def _from_text_for(cls, text, dist):
return (ep._for(dist) for ep in cls._from_text(text))

def _for(self, dist):
self.dist = dist
return self

def __iter__(self):
"""
Expand All @@ -132,7 +138,7 @@ def __reduce__(self):
return (
self.__class__,
(self.name, self.value, self.group),
)
)


class PackagePath(pathlib.PurePosixPath):
Expand All @@ -159,6 +165,25 @@ def __repr__(self):
return '<FileHash mode: {} value: {}>'.format(self.mode, self.value)


_T = TypeVar("_T")


class PackageMetadata(Protocol):
def __len__(self) -> int:
... # pragma: no cover

def __contains__(self, item: str) -> bool:
... # pragma: no cover

def __getitem__(self, key: str) -> str:
... # pragma: no cover

def get_all(self, name: str, failobj: _T = ...) -> Union[List[Any], _T]:
"""
Return all values associated with a possibly multi-valued key.
"""


class Distribution:
"""A Python distribution package."""

Expand Down Expand Up @@ -210,9 +235,8 @@ def discover(cls, **kwargs):
raise ValueError("cannot accept context and kwargs")
context = context or DistributionFinder.Context(**kwargs)
return itertools.chain.from_iterable(
resolver(context)
for resolver in cls._discover_resolvers()
)
resolver(context) for resolver in cls._discover_resolvers()
)

@staticmethod
def at(path):
Expand All @@ -227,24 +251,24 @@ def at(path):
def _discover_resolvers():
"""Search the meta_path for resolvers."""
declared = (
getattr(finder, 'find_distributions', None)
for finder in sys.meta_path
)
getattr(finder, 'find_distributions', None) for finder in sys.meta_path
)
return filter(None, declared)

@classmethod
def _local(cls, root='.'):
from pep517 import build, meta

system = build.compat_system(root)
builder = functools.partial(
meta.build,
source_dir=root,
system=system,
)
)
return PathDistribution(zipfile.Path(meta.build_as_zip(builder)))

@property
def metadata(self):
def metadata(self) -> PackageMetadata:
"""Return the parsed metadata for this Distribution.

The returned object will have keys that name the various bits of
Expand All @@ -257,17 +281,22 @@ def metadata(self):
# effect is to just end up using the PathDistribution's self._path
# (which points to the egg-info file) attribute unchanged.
or self.read_text('')
)
)
return email.message_from_string(text)

@property
def name(self):
"""Return the 'Name' metadata for the distribution package."""
return self.metadata['Name']

@property
def version(self):
"""Return the 'Version' metadata for the distribution package."""
return self.metadata['Version']

@property
def entry_points(self):
return EntryPoint._from_text(self.read_text('entry_points.txt'))
return list(EntryPoint._from_text_for(self.read_text('entry_points.txt'), self))

@property
def files(self):
Expand Down Expand Up @@ -324,9 +353,10 @@ def _deps_from_requires_text(cls, source):
section_pairs = cls._read_sections(source.splitlines())
sections = {
section: list(map(operator.itemgetter('line'), results))
for section, results in
itertools.groupby(section_pairs, operator.itemgetter('section'))
}
for section, results in itertools.groupby(
section_pairs, operator.itemgetter('section')
)
}
return cls._convert_egg_info_reqs_to_simple_reqs(sections)

@staticmethod
Expand All @@ -350,6 +380,7 @@ def _convert_egg_info_reqs_to_simple_reqs(sections):
requirement. This method converts the former to the
latter. See _test_deps_from_requires_text for an example.
"""

def make_condition(name):
return name and 'extra == "{name}"'.format(name=name)

Expand Down Expand Up @@ -438,48 +469,69 @@ def zip_children(self):
names = zip_path.root.namelist()
self.joinpath = zip_path.joinpath

return dict.fromkeys(
child.split(posixpath.sep, 1)[0]
for child in names
)

def is_egg(self, search):
base = self.base
return (
base == search.versionless_egg_name
or base.startswith(search.prefix)
and base.endswith('.egg'))
return dict.fromkeys(child.split(posixpath.sep, 1)[0] for child in names)

def search(self, name):
for child in self.children():
n_low = child.lower()
if (n_low in name.exact_matches
or n_low.startswith(name.prefix)
and n_low.endswith(name.suffixes)
# legacy case:
or self.is_egg(name) and n_low == 'egg-info'):
yield self.joinpath(child)
return (
self.joinpath(child)
for child in self.children()
if name.matches(child, self.base)
)


class Prepared:
"""
A prepared search for metadata on a possibly-named package.
"""
normalized = ''
prefix = ''

normalized = None
suffixes = '.dist-info', '.egg-info'
exact_matches = [''][:0]
versionless_egg_name = ''

def __init__(self, name):
self.name = name
if name is None:
return
self.normalized = name.lower().replace('-', '_')
self.prefix = self.normalized + '-'
self.exact_matches = [
self.normalized + suffix for suffix in self.suffixes]
self.versionless_egg_name = self.normalized + '.egg'
self.normalized = self.normalize(name)
self.exact_matches = [self.normalized + suffix for suffix in self.suffixes]

@staticmethod
def normalize(name):
"""
PEP 503 normalization plus dashes as underscores.
"""
return re.sub(r"[-_.]+", "-", name).lower().replace('-', '_')

@staticmethod
def legacy_normalize(name):
"""
Normalize the package name as found in the convention in
older packaging tools versions and specs.
"""
return name.lower().replace('-', '_')

def matches(self, cand, base):
low = cand.lower()
pre, ext = os.path.splitext(low)
name, sep, rest = pre.partition('-')
return (
low in self.exact_matches
or ext in self.suffixes
and (not self.normalized or name.replace('.', '_') == self.normalized)
# legacy case:
or self.is_egg(base)
and low == 'egg-info'
)

def is_egg(self, base):
normalized = self.legacy_normalize(self.name or '')
prefix = normalized + '-' if normalized else ''
versionless_egg_name = normalized + '.egg' if self.name else ''
return (
base == versionless_egg_name
or base.startswith(prefix)
and base.endswith('.egg')
)


class MetadataPathFinder(DistributionFinder):
Expand All @@ -500,9 +552,8 @@ def find_distributions(cls, context=DistributionFinder.Context()):
def _search_paths(cls, name, paths):
"""Find metadata directories in paths heuristically."""
return itertools.chain.from_iterable(
path.search(Prepared(name))
for path in map(FastPath, paths)
)
path.search(Prepared(name)) for path in map(FastPath, paths)
)


class PathDistribution(Distribution):
Expand All @@ -515,9 +566,15 @@ def __init__(self, path):
self._path = path

def read_text(self, filename):
with suppress(FileNotFoundError, IsADirectoryError, KeyError,
NotADirectoryError, PermissionError):
with suppress(
FileNotFoundError,
IsADirectoryError,
KeyError,
NotADirectoryError,
PermissionError,
):
return self._path.joinpath(filename).read_text(encoding='utf-8')

read_text.__doc__ = Distribution.read_text.__doc__

def locate_file(self, path):
Expand All @@ -541,11 +598,11 @@ def distributions(**kwargs):
return Distribution.discover(**kwargs)


def metadata(distribution_name):
def metadata(distribution_name) -> PackageMetadata:
"""Get the metadata for the named package.

:param distribution_name: The name of the distribution package to query.
:return: An email.Message containing the parsed metadata.
:return: A PackageMetadata containing the parsed metadata.
"""
return Distribution.from_name(distribution_name).metadata

Expand All @@ -565,15 +622,11 @@ def entry_points():

:return: EntryPoint objects for all installed packages.
"""
eps = itertools.chain.from_iterable(
dist.entry_points for dist in distributions())
eps = itertools.chain.from_iterable(dist.entry_points for dist in distributions())
by_group = operator.attrgetter('group')
ordered = sorted(eps, key=by_group)
grouped = itertools.groupby(ordered, by_group)
return {
group: tuple(eps)
for group, eps in grouped
}
return {group: tuple(eps) for group, eps in grouped}


def files(distribution_name):
Expand Down
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