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+from __future__ import annotations
+
+import email.feedparser
+import email.header
+import email.message
+import email.parser
+import email.policy
+import pathlib
+import sys
+import typing
+from typing import (
+ Any,
+ Callable,
+ Generic,
+ Literal,
+ TypedDict,
+ cast,
+)
+
+from . import licenses, requirements, specifiers, utils
+from . import version as version_module
+from .licenses import NormalizedLicenseExpression
+
+T = typing.TypeVar("T")
+
+
+if sys.version_info >= (3, 11): # pragma: no cover
+ ExceptionGroup = ExceptionGroup
+else: # pragma: no cover
+
+ class ExceptionGroup(Exception):
+ """A minimal implementation of :external:exc:`ExceptionGroup` from Python 3.11.
+
+ If :external:exc:`ExceptionGroup` is already defined by Python itself,
+ that version is used instead.
+ """
+
+ message: str
+ exceptions: list[Exception]
+
+ def __init__(self, message: str, exceptions: list[Exception]) -> None:
+ self.message = message
+ self.exceptions = exceptions
+
+ def __repr__(self) -> str:
+ return f"{self.__class__.__name__}({self.message!r}, {self.exceptions!r})"
+
+
+class InvalidMetadata(ValueError):
+ """A metadata field contains invalid data."""
+
+ field: str
+ """The name of the field that contains invalid data."""
+
+ def __init__(self, field: str, message: str) -> None:
+ self.field = field
+ super().__init__(message)
+
+
+# The RawMetadata class attempts to make as few assumptions about the underlying
+# serialization formats as possible. The idea is that as long as a serialization
+# formats offer some very basic primitives in *some* way then we can support
+# serializing to and from that format.
+class RawMetadata(TypedDict, total=False):
+ """A dictionary of raw core metadata.
+
+ Each field in core metadata maps to a key of this dictionary (when data is
+ provided). The key is lower-case and underscores are used instead of dashes
+ compared to the equivalent core metadata field. Any core metadata field that
+ can be specified multiple times or can hold multiple values in a single
+ field have a key with a plural name. See :class:`Metadata` whose attributes
+ match the keys of this dictionary.
+
+ Core metadata fields that can be specified multiple times are stored as a
+ list or dict depending on which is appropriate for the field. Any fields
+ which hold multiple values in a single field are stored as a list.
+
+ """
+
+ # Metadata 1.0 - PEP 241
+ metadata_version: str
+ name: str
+ version: str
+ platforms: list[str]
+ summary: str
+ description: str
+ keywords: list[str]
+ home_page: str
+ author: str
+ author_email: str
+ license: str
+
+ # Metadata 1.1 - PEP 314
+ supported_platforms: list[str]
+ download_url: str
+ classifiers: list[str]
+ requires: list[str]
+ provides: list[str]
+ obsoletes: list[str]
+
+ # Metadata 1.2 - PEP 345
+ maintainer: str
+ maintainer_email: str
+ requires_dist: list[str]
+ provides_dist: list[str]
+ obsoletes_dist: list[str]
+ requires_python: str
+ requires_external: list[str]
+ project_urls: dict[str, str]
+
+ # Metadata 2.0
+ # PEP 426 attempted to completely revamp the metadata format
+ # but got stuck without ever being able to build consensus on
+ # it and ultimately ended up withdrawn.
+ #
+ # However, a number of tools had started emitting METADATA with
+ # `2.0` Metadata-Version, so for historical reasons, this version
+ # was skipped.
+
+ # Metadata 2.1 - PEP 566
+ description_content_type: str
+ provides_extra: list[str]
+
+ # Metadata 2.2 - PEP 643
+ dynamic: list[str]
+
+ # Metadata 2.3 - PEP 685
+ # No new fields were added in PEP 685, just some edge case were
+ # tightened up to provide better interoptability.
+
+ # Metadata 2.4 - PEP 639
+ license_expression: str
+ license_files: list[str]
+
+
+_STRING_FIELDS = {
+ "author",
+ "author_email",
+ "description",
+ "description_content_type",
+ "download_url",
+ "home_page",
+ "license",
+ "license_expression",
+ "maintainer",
+ "maintainer_email",
+ "metadata_version",
+ "name",
+ "requires_python",
+ "summary",
+ "version",
+}
+
+_LIST_FIELDS = {
+ "classifiers",
+ "dynamic",
+ "license_files",
+ "obsoletes",
+ "obsoletes_dist",
+ "platforms",
+ "provides",
+ "provides_dist",
+ "provides_extra",
+ "requires",
+ "requires_dist",
+ "requires_external",
+ "supported_platforms",
+}
+
+_DICT_FIELDS = {
+ "project_urls",
+}
+
+
+def _parse_keywords(data: str) -> list[str]:
+ """Split a string of comma-separated keywords into a list of keywords."""
+ return [k.strip() for k in data.split(",")]
+
+
+def _parse_project_urls(data: list[str]) -> dict[str, str]:
+ """Parse a list of label/URL string pairings separated by a comma."""
+ urls = {}
+ for pair in data:
+ # Our logic is slightly tricky here as we want to try and do
+ # *something* reasonable with malformed data.
+ #
+ # The main thing that we have to worry about, is data that does
+ # not have a ',' at all to split the label from the Value. There
+ # isn't a singular right answer here, and we will fail validation
+ # later on (if the caller is validating) so it doesn't *really*
+ # matter, but since the missing value has to be an empty str
+ # and our return value is dict[str, str], if we let the key
+ # be the missing value, then they'd have multiple '' values that
+ # overwrite each other in a accumulating dict.
+ #
+ # The other potentional issue is that it's possible to have the
+ # same label multiple times in the metadata, with no solid "right"
+ # answer with what to do in that case. As such, we'll do the only
+ # thing we can, which is treat the field as unparseable and add it
+ # to our list of unparsed fields.
+ parts = [p.strip() for p in pair.split(",", 1)]
+ parts.extend([""] * (max(0, 2 - len(parts)))) # Ensure 2 items
+
+ # TODO: The spec doesn't say anything about if the keys should be
+ # considered case sensitive or not... logically they should
+ # be case-preserving and case-insensitive, but doing that
+ # would open up more cases where we might have duplicate
+ # entries.
+ label, url = parts
+ if label in urls:
+ # The label already exists in our set of urls, so this field
+ # is unparseable, and we can just add the whole thing to our
+ # unparseable data and stop processing it.
+ raise KeyError("duplicate labels in project urls")
+ urls[label] = url
+
+ return urls
+
+
+def _get_payload(msg: email.message.Message, source: bytes | str) -> str:
+ """Get the body of the message."""
+ # If our source is a str, then our caller has managed encodings for us,
+ # and we don't need to deal with it.
+ if isinstance(source, str):
+ payload = msg.get_payload()
+ assert isinstance(payload, str)
+ return payload
+ # If our source is a bytes, then we're managing the encoding and we need
+ # to deal with it.
+ else:
+ bpayload = msg.get_payload(decode=True)
+ assert isinstance(bpayload, bytes)
+ try:
+ return bpayload.decode("utf8", "strict")
+ except UnicodeDecodeError as exc:
+ raise ValueError("payload in an invalid encoding") from exc
+
+
+# The various parse_FORMAT functions here are intended to be as lenient as
+# possible in their parsing, while still returning a correctly typed
+# RawMetadata.
+#
+# To aid in this, we also generally want to do as little touching of the
+# data as possible, except where there are possibly some historic holdovers
+# that make valid data awkward to work with.
+#
+# While this is a lower level, intermediate format than our ``Metadata``
+# class, some light touch ups can make a massive difference in usability.
+
+# Map METADATA fields to RawMetadata.
+_EMAIL_TO_RAW_MAPPING = {
+ "author": "author",
+ "author-email": "author_email",
+ "classifier": "classifiers",
+ "description": "description",
+ "description-content-type": "description_content_type",
+ "download-url": "download_url",
+ "dynamic": "dynamic",
+ "home-page": "home_page",
+ "keywords": "keywords",
+ "license": "license",
+ "license-expression": "license_expression",
+ "license-file": "license_files",
+ "maintainer": "maintainer",
+ "maintainer-email": "maintainer_email",
+ "metadata-version": "metadata_version",
+ "name": "name",
+ "obsoletes": "obsoletes",
+ "obsoletes-dist": "obsoletes_dist",
+ "platform": "platforms",
+ "project-url": "project_urls",
+ "provides": "provides",
+ "provides-dist": "provides_dist",
+ "provides-extra": "provides_extra",
+ "requires": "requires",
+ "requires-dist": "requires_dist",
+ "requires-external": "requires_external",
+ "requires-python": "requires_python",
+ "summary": "summary",
+ "supported-platform": "supported_platforms",
+ "version": "version",
+}
+_RAW_TO_EMAIL_MAPPING = {raw: email for email, raw in _EMAIL_TO_RAW_MAPPING.items()}
+
+
+def parse_email(data: bytes | str) -> tuple[RawMetadata, dict[str, list[str]]]:
+ """Parse a distribution's metadata stored as email headers (e.g. from ``METADATA``).
+
+ This function returns a two-item tuple of dicts. The first dict is of
+ recognized fields from the core metadata specification. Fields that can be
+ parsed and translated into Python's built-in types are converted
+ appropriately. All other fields are left as-is. Fields that are allowed to
+ appear multiple times are stored as lists.
+
+ The second dict contains all other fields from the metadata. This includes
+ any unrecognized fields. It also includes any fields which are expected to
+ be parsed into a built-in type but were not formatted appropriately. Finally,
+ any fields that are expected to appear only once but are repeated are
+ included in this dict.
+
+ """
+ raw: dict[str, str | list[str] | dict[str, str]] = {}
+ unparsed: dict[str, list[str]] = {}
+
+ if isinstance(data, str):
+ parsed = email.parser.Parser(policy=email.policy.compat32).parsestr(data)
+ else:
+ parsed = email.parser.BytesParser(policy=email.policy.compat32).parsebytes(data)
+
+ # We have to wrap parsed.keys() in a set, because in the case of multiple
+ # values for a key (a list), the key will appear multiple times in the
+ # list of keys, but we're avoiding that by using get_all().
+ for name in frozenset(parsed.keys()):
+ # Header names in RFC are case insensitive, so we'll normalize to all
+ # lower case to make comparisons easier.
+ name = name.lower()
+
+ # We use get_all() here, even for fields that aren't multiple use,
+ # because otherwise someone could have e.g. two Name fields, and we
+ # would just silently ignore it rather than doing something about it.
+ headers = parsed.get_all(name) or []
+
+ # The way the email module works when parsing bytes is that it
+ # unconditionally decodes the bytes as ascii using the surrogateescape
+ # handler. When you pull that data back out (such as with get_all() ),
+ # it looks to see if the str has any surrogate escapes, and if it does
+ # it wraps it in a Header object instead of returning the string.
+ #
+ # As such, we'll look for those Header objects, and fix up the encoding.
+ value = []
+ # Flag if we have run into any issues processing the headers, thus
+ # signalling that the data belongs in 'unparsed'.
+ valid_encoding = True
+ for h in headers:
+ # It's unclear if this can return more types than just a Header or
+ # a str, so we'll just assert here to make sure.
+ assert isinstance(h, (email.header.Header, str))
+
+ # If it's a header object, we need to do our little dance to get
+ # the real data out of it. In cases where there is invalid data
+ # we're going to end up with mojibake, but there's no obvious, good
+ # way around that without reimplementing parts of the Header object
+ # ourselves.
+ #
+ # That should be fine since, if mojibacked happens, this key is
+ # going into the unparsed dict anyways.
+ if isinstance(h, email.header.Header):
+ # The Header object stores it's data as chunks, and each chunk
+ # can be independently encoded, so we'll need to check each
+ # of them.
+ chunks: list[tuple[bytes, str | None]] = []
+ for bin, encoding in email.header.decode_header(h):
+ try:
+ bin.decode("utf8", "strict")
+ except UnicodeDecodeError:
+ # Enable mojibake.
+ encoding = "latin1"
+ valid_encoding = False
+ else:
+ encoding = "utf8"
+ chunks.append((bin, encoding))
+
+ # Turn our chunks back into a Header object, then let that
+ # Header object do the right thing to turn them into a
+ # string for us.
+ value.append(str(email.header.make_header(chunks)))
+ # This is already a string, so just add it.
+ else:
+ value.append(h)
+
+ # We've processed all of our values to get them into a list of str,
+ # but we may have mojibake data, in which case this is an unparsed
+ # field.
+ if not valid_encoding:
+ unparsed[name] = value
+ continue
+
+ raw_name = _EMAIL_TO_RAW_MAPPING.get(name)
+ if raw_name is None:
+ # This is a bit of a weird situation, we've encountered a key that
+ # we don't know what it means, so we don't know whether it's meant
+ # to be a list or not.
+ #
+ # Since we can't really tell one way or another, we'll just leave it
+ # as a list, even though it may be a single item list, because that's
+ # what makes the most sense for email headers.
+ unparsed[name] = value
+ continue
+
+ # If this is one of our string fields, then we'll check to see if our
+ # value is a list of a single item. If it is then we'll assume that
+ # it was emitted as a single string, and unwrap the str from inside
+ # the list.
+ #
+ # If it's any other kind of data, then we haven't the faintest clue
+ # what we should parse it as, and we have to just add it to our list
+ # of unparsed stuff.
+ if raw_name in _STRING_FIELDS and len(value) == 1:
+ raw[raw_name] = value[0]
+ # If this is one of our list of string fields, then we can just assign
+ # the value, since email *only* has strings, and our get_all() call
+ # above ensures that this is a list.
+ elif raw_name in _LIST_FIELDS:
+ raw[raw_name] = value
+ # Special Case: Keywords
+ # The keywords field is implemented in the metadata spec as a str,
+ # but it conceptually is a list of strings, and is serialized using
+ # ", ".join(keywords), so we'll do some light data massaging to turn
+ # this into what it logically is.
+ elif raw_name == "keywords" and len(value) == 1:
+ raw[raw_name] = _parse_keywords(value[0])
+ # Special Case: Project-URL
+ # The project urls is implemented in the metadata spec as a list of
+ # specially-formatted strings that represent a key and a value, which
+ # is fundamentally a mapping, however the email format doesn't support
+ # mappings in a sane way, so it was crammed into a list of strings
+ # instead.
+ #
+ # We will do a little light data massaging to turn this into a map as
+ # it logically should be.
+ elif raw_name == "project_urls":
+ try:
+ raw[raw_name] = _parse_project_urls(value)
+ except KeyError:
+ unparsed[name] = value
+ # Nothing that we've done has managed to parse this, so it'll just
+ # throw it in our unparseable data and move on.
+ else:
+ unparsed[name] = value
+
+ # We need to support getting the Description from the message payload in
+ # addition to getting it from the the headers. This does mean, though, there
+ # is the possibility of it being set both ways, in which case we put both
+ # in 'unparsed' since we don't know which is right.
+ try:
+ payload = _get_payload(parsed, data)
+ except ValueError:
+ unparsed.setdefault("description", []).append(
+ parsed.get_payload(decode=isinstance(data, bytes)) # type: ignore[call-overload]
+ )
+ else:
+ if payload:
+ # Check to see if we've already got a description, if so then both
+ # it, and this body move to unparseable.
+ if "description" in raw:
+ description_header = cast(str, raw.pop("description"))
+ unparsed.setdefault("description", []).extend(
+ [description_header, payload]
+ )
+ elif "description" in unparsed:
+ unparsed["description"].append(payload)
+ else:
+ raw["description"] = payload
+
+ # We need to cast our `raw` to a metadata, because a TypedDict only support
+ # literal key names, but we're computing our key names on purpose, but the
+ # way this function is implemented, our `TypedDict` can only have valid key
+ # names.
+ return cast(RawMetadata, raw), unparsed
+
+
+_NOT_FOUND = object()
+
+
+# Keep the two values in sync.
+_VALID_METADATA_VERSIONS = ["1.0", "1.1", "1.2", "2.1", "2.2", "2.3", "2.4"]
+_MetadataVersion = Literal["1.0", "1.1", "1.2", "2.1", "2.2", "2.3", "2.4"]
+
+_REQUIRED_ATTRS = frozenset(["metadata_version", "name", "version"])
+
+
+class _Validator(Generic[T]):
+ """Validate a metadata field.
+
+ All _process_*() methods correspond to a core metadata field. The method is
+ called with the field's raw value. If the raw value is valid it is returned
+ in its "enriched" form (e.g. ``version.Version`` for the ``Version`` field).
+ If the raw value is invalid, :exc:`InvalidMetadata` is raised (with a cause
+ as appropriate).
+ """
+
+ name: str
+ raw_name: str
+ added: _MetadataVersion
+
+ def __init__(
+ self,
+ *,
+ added: _MetadataVersion = "1.0",
+ ) -> None:
+ self.added = added
+
+ def __set_name__(self, _owner: Metadata, name: str) -> None:
+ self.name = name
+ self.raw_name = _RAW_TO_EMAIL_MAPPING[name]
+
+ def __get__(self, instance: Metadata, _owner: type[Metadata]) -> T:
+ # With Python 3.8, the caching can be replaced with functools.cached_property().
+ # No need to check the cache as attribute lookup will resolve into the
+ # instance's __dict__ before __get__ is called.
+ cache = instance.__dict__
+ value = instance._raw.get(self.name)
+
+ # To make the _process_* methods easier, we'll check if the value is None
+ # and if this field is NOT a required attribute, and if both of those
+ # things are true, we'll skip the the converter. This will mean that the
+ # converters never have to deal with the None union.
+ if self.name in _REQUIRED_ATTRS or value is not None:
+ try:
+ converter: Callable[[Any], T] = getattr(self, f"_process_{self.name}")
+ except AttributeError:
+ pass
+ else:
+ value = converter(value)
+
+ cache[self.name] = value
+ try:
+ del instance._raw[self.name] # type: ignore[misc]
+ except KeyError:
+ pass
+
+ return cast(T, value)
+
+ def _invalid_metadata(
+ self, msg: str, cause: Exception | None = None
+ ) -> InvalidMetadata:
+ exc = InvalidMetadata(
+ self.raw_name, msg.format_map({"field": repr(self.raw_name)})
+ )
+ exc.__cause__ = cause
+ return exc
+
+ def _process_metadata_version(self, value: str) -> _MetadataVersion:
+ # Implicitly makes Metadata-Version required.
+ if value not in _VALID_METADATA_VERSIONS:
+ raise self._invalid_metadata(f"{value!r} is not a valid metadata version")
+ return cast(_MetadataVersion, value)
+
+ def _process_name(self, value: str) -> str:
+ if not value:
+ raise self._invalid_metadata("{field} is a required field")
+ # Validate the name as a side-effect.
+ try:
+ utils.canonicalize_name(value, validate=True)
+ except utils.InvalidName as exc:
+ raise self._invalid_metadata(
+ f"{value!r} is invalid for {{field}}", cause=exc
+ ) from exc
+ else:
+ return value
+
+ def _process_version(self, value: str) -> version_module.Version:
+ if not value:
+ raise self._invalid_metadata("{field} is a required field")
+ try:
+ return version_module.parse(value)
+ except version_module.InvalidVersion as exc:
+ raise self._invalid_metadata(
+ f"{value!r} is invalid for {{field}}", cause=exc
+ ) from exc
+
+ def _process_summary(self, value: str) -> str:
+ """Check the field contains no newlines."""
+ if "\n" in value:
+ raise self._invalid_metadata("{field} must be a single line")
+ return value
+
+ def _process_description_content_type(self, value: str) -> str:
+ content_types = {"text/plain", "text/x-rst", "text/markdown"}
+ message = email.message.EmailMessage()
+ message["content-type"] = value
+
+ content_type, parameters = (
+ # Defaults to `text/plain` if parsing failed.
+ message.get_content_type().lower(),
+ message["content-type"].params,
+ )
+ # Check if content-type is valid or defaulted to `text/plain` and thus was
+ # not parseable.
+ if content_type not in content_types or content_type not in value.lower():
+ raise self._invalid_metadata(
+ f"{{field}} must be one of {list(content_types)}, not {value!r}"
+ )
+
+ charset = parameters.get("charset", "UTF-8")
+ if charset != "UTF-8":
+ raise self._invalid_metadata(
+ f"{{field}} can only specify the UTF-8 charset, not {list(charset)}"
+ )
+
+ markdown_variants = {"GFM", "CommonMark"}
+ variant = parameters.get("variant", "GFM") # Use an acceptable default.
+ if content_type == "text/markdown" and variant not in markdown_variants:
+ raise self._invalid_metadata(
+ f"valid Markdown variants for {{field}} are {list(markdown_variants)}, "
+ f"not {variant!r}",
+ )
+ return value
+
+ def _process_dynamic(self, value: list[str]) -> list[str]:
+ for dynamic_field in map(str.lower, value):
+ if dynamic_field in {"name", "version", "metadata-version"}:
+ raise self._invalid_metadata(
+ f"{dynamic_field!r} is not allowed as a dynamic field"
+ )
+ elif dynamic_field not in _EMAIL_TO_RAW_MAPPING:
+ raise self._invalid_metadata(
+ f"{dynamic_field!r} is not a valid dynamic field"
+ )
+ return list(map(str.lower, value))
+
+ def _process_provides_extra(
+ self,
+ value: list[str],
+ ) -> list[utils.NormalizedName]:
+ normalized_names = []
+ try:
+ for name in value:
+ normalized_names.append(utils.canonicalize_name(name, validate=True))
+ except utils.InvalidName as exc:
+ raise self._invalid_metadata(
+ f"{name!r} is invalid for {{field}}", cause=exc
+ ) from exc
+ else:
+ return normalized_names
+
+ def _process_requires_python(self, value: str) -> specifiers.SpecifierSet:
+ try:
+ return specifiers.SpecifierSet(value)
+ except specifiers.InvalidSpecifier as exc:
+ raise self._invalid_metadata(
+ f"{value!r} is invalid for {{field}}", cause=exc
+ ) from exc
+
+ def _process_requires_dist(
+ self,
+ value: list[str],
+ ) -> list[requirements.Requirement]:
+ reqs = []
+ try:
+ for req in value:
+ reqs.append(requirements.Requirement(req))
+ except requirements.InvalidRequirement as exc:
+ raise self._invalid_metadata(
+ f"{req!r} is invalid for {{field}}", cause=exc
+ ) from exc
+ else:
+ return reqs
+
+ def _process_license_expression(
+ self, value: str
+ ) -> NormalizedLicenseExpression | None:
+ try:
+ return licenses.canonicalize_license_expression(value)
+ except ValueError as exc:
+ raise self._invalid_metadata(
+ f"{value!r} is invalid for {{field}}", cause=exc
+ ) from exc
+
+ def _process_license_files(self, value: list[str]) -> list[str]:
+ paths = []
+ for path in value:
+ if ".." in path:
+ raise self._invalid_metadata(
+ f"{path!r} is invalid for {{field}}, "
+ "parent directory indicators are not allowed"
+ )
+ if "*" in path:
+ raise self._invalid_metadata(
+ f"{path!r} is invalid for {{field}}, paths must be resolved"
+ )
+ if (
+ pathlib.PurePosixPath(path).is_absolute()
+ or pathlib.PureWindowsPath(path).is_absolute()
+ ):
+ raise self._invalid_metadata(
+ f"{path!r} is invalid for {{field}}, paths must be relative"
+ )
+ if pathlib.PureWindowsPath(path).as_posix() != path:
+ raise self._invalid_metadata(
+ f"{path!r} is invalid for {{field}}, "
+ "paths must use '/' delimiter"
+ )
+ paths.append(path)
+ return paths
+
+
+class Metadata:
+ """Representation of distribution metadata.
+
+ Compared to :class:`RawMetadata`, this class provides objects representing
+ metadata fields instead of only using built-in types. Any invalid metadata
+ will cause :exc:`InvalidMetadata` to be raised (with a
+ :py:attr:`~BaseException.__cause__` attribute as appropriate).
+ """
+
+ _raw: RawMetadata
+
+ @classmethod
+ def from_raw(cls, data: RawMetadata, *, validate: bool = True) -> Metadata:
+ """Create an instance from :class:`RawMetadata`.
+
+ If *validate* is true, all metadata will be validated. All exceptions
+ related to validation will be gathered and raised as an :class:`ExceptionGroup`.
+ """
+ ins = cls()
+ ins._raw = data.copy() # Mutations occur due to caching enriched values.
+
+ if validate:
+ exceptions: list[Exception] = []
+ try:
+ metadata_version = ins.metadata_version
+ metadata_age = _VALID_METADATA_VERSIONS.index(metadata_version)
+ except InvalidMetadata as metadata_version_exc:
+ exceptions.append(metadata_version_exc)
+ metadata_version = None
+
+ # Make sure to check for the fields that are present, the required
+ # fields (so their absence can be reported).
+ fields_to_check = frozenset(ins._raw) | _REQUIRED_ATTRS
+ # Remove fields that have already been checked.
+ fields_to_check -= {"metadata_version"}
+
+ for key in fields_to_check:
+ try:
+ if metadata_version:
+ # Can't use getattr() as that triggers descriptor protocol which
+ # will fail due to no value for the instance argument.
+ try:
+ field_metadata_version = cls.__dict__[key].added
+ except KeyError:
+ exc = InvalidMetadata(key, f"unrecognized field: {key!r}")
+ exceptions.append(exc)
+ continue
+ field_age = _VALID_METADATA_VERSIONS.index(
+ field_metadata_version
+ )
+ if field_age > metadata_age:
+ field = _RAW_TO_EMAIL_MAPPING[key]
+ exc = InvalidMetadata(
+ field,
+ f"{field} introduced in metadata version "
+ f"{field_metadata_version}, not {metadata_version}",
+ )
+ exceptions.append(exc)
+ continue
+ getattr(ins, key)
+ except InvalidMetadata as exc:
+ exceptions.append(exc)
+
+ if exceptions:
+ raise ExceptionGroup("invalid metadata", exceptions)
+
+ return ins
+
+ @classmethod
+ def from_email(cls, data: bytes | str, *, validate: bool = True) -> Metadata:
+ """Parse metadata from email headers.
+
+ If *validate* is true, the metadata will be validated. All exceptions
+ related to validation will be gathered and raised as an :class:`ExceptionGroup`.
+ """
+ raw, unparsed = parse_email(data)
+
+ if validate:
+ exceptions: list[Exception] = []
+ for unparsed_key in unparsed:
+ if unparsed_key in _EMAIL_TO_RAW_MAPPING:
+ message = f"{unparsed_key!r} has invalid data"
+ else:
+ message = f"unrecognized field: {unparsed_key!r}"
+ exceptions.append(InvalidMetadata(unparsed_key, message))
+
+ if exceptions:
+ raise ExceptionGroup("unparsed", exceptions)
+
+ try:
+ return cls.from_raw(raw, validate=validate)
+ except ExceptionGroup as exc_group:
+ raise ExceptionGroup(
+ "invalid or unparsed metadata", exc_group.exceptions
+ ) from None
+
+ metadata_version: _Validator[_MetadataVersion] = _Validator()
+ """:external:ref:`core-metadata-metadata-version`
+ (required; validated to be a valid metadata version)"""
+ # `name` is not normalized/typed to NormalizedName so as to provide access to
+ # the original/raw name.
+ name: _Validator[str] = _Validator()
+ """:external:ref:`core-metadata-name`
+ (required; validated using :func:`~packaging.utils.canonicalize_name` and its
+ *validate* parameter)"""
+ version: _Validator[version_module.Version] = _Validator()
+ """:external:ref:`core-metadata-version` (required)"""
+ dynamic: _Validator[list[str] | None] = _Validator(
+ added="2.2",
+ )
+ """:external:ref:`core-metadata-dynamic`
+ (validated against core metadata field names and lowercased)"""
+ platforms: _Validator[list[str] | None] = _Validator()
+ """:external:ref:`core-metadata-platform`"""
+ supported_platforms: _Validator[list[str] | None] = _Validator(added="1.1")
+ """:external:ref:`core-metadata-supported-platform`"""
+ summary: _Validator[str | None] = _Validator()
+ """:external:ref:`core-metadata-summary` (validated to contain no newlines)"""
+ description: _Validator[str | None] = _Validator() # TODO 2.1: can be in body
+ """:external:ref:`core-metadata-description`"""
+ description_content_type: _Validator[str | None] = _Validator(added="2.1")
+ """:external:ref:`core-metadata-description-content-type` (validated)"""
+ keywords: _Validator[list[str] | None] = _Validator()
+ """:external:ref:`core-metadata-keywords`"""
+ home_page: _Validator[str | None] = _Validator()
+ """:external:ref:`core-metadata-home-page`"""
+ download_url: _Validator[str | None] = _Validator(added="1.1")
+ """:external:ref:`core-metadata-download-url`"""
+ author: _Validator[str | None] = _Validator()
+ """:external:ref:`core-metadata-author`"""
+ author_email: _Validator[str | None] = _Validator()
+ """:external:ref:`core-metadata-author-email`"""
+ maintainer: _Validator[str | None] = _Validator(added="1.2")
+ """:external:ref:`core-metadata-maintainer`"""
+ maintainer_email: _Validator[str | None] = _Validator(added="1.2")
+ """:external:ref:`core-metadata-maintainer-email`"""
+ license: _Validator[str | None] = _Validator()
+ """:external:ref:`core-metadata-license`"""
+ license_expression: _Validator[NormalizedLicenseExpression | None] = _Validator(
+ added="2.4"
+ )
+ """:external:ref:`core-metadata-license-expression`"""
+ license_files: _Validator[list[str] | None] = _Validator(added="2.4")
+ """:external:ref:`core-metadata-license-file`"""
+ classifiers: _Validator[list[str] | None] = _Validator(added="1.1")
+ """:external:ref:`core-metadata-classifier`"""
+ requires_dist: _Validator[list[requirements.Requirement] | None] = _Validator(
+ added="1.2"
+ )
+ """:external:ref:`core-metadata-requires-dist`"""
+ requires_python: _Validator[specifiers.SpecifierSet | None] = _Validator(
+ added="1.2"
+ )
+ """:external:ref:`core-metadata-requires-python`"""
+ # Because `Requires-External` allows for non-PEP 440 version specifiers, we
+ # don't do any processing on the values.
+ requires_external: _Validator[list[str] | None] = _Validator(added="1.2")
+ """:external:ref:`core-metadata-requires-external`"""
+ project_urls: _Validator[dict[str, str] | None] = _Validator(added="1.2")
+ """:external:ref:`core-metadata-project-url`"""
+ # PEP 685 lets us raise an error if an extra doesn't pass `Name` validation
+ # regardless of metadata version.
+ provides_extra: _Validator[list[utils.NormalizedName] | None] = _Validator(
+ added="2.1",
+ )
+ """:external:ref:`core-metadata-provides-extra`"""
+ provides_dist: _Validator[list[str] | None] = _Validator(added="1.2")
+ """:external:ref:`core-metadata-provides-dist`"""
+ obsoletes_dist: _Validator[list[str] | None] = _Validator(added="1.2")
+ """:external:ref:`core-metadata-obsoletes-dist`"""
+ requires: _Validator[list[str] | None] = _Validator(added="1.1")
+ """``Requires`` (deprecated)"""
+ provides: _Validator[list[str] | None] = _Validator(added="1.1")
+ """``Provides`` (deprecated)"""
+ obsoletes: _Validator[list[str] | None] = _Validator(added="1.1")
+ """``Obsoletes`` (deprecated)"""