Reapply "gh-132947: Apply changes from importlib_metadata 8.7 (#137885)" (#137924)

This reverts commit 3706ef6.

Author: jaraco

Lib/importlib/metadata/__init__.py

@@ -1,11 +1,58 @@
+import email.message
+import email.policy
 import re
 import textwrap
-import email.message
 
 from ._text import FoldedCase
 
 
+class RawPolicy(email.policy.EmailPolicy):
+    def fold(self, name, value):
+        folded = self.linesep.join(
+            textwrap.indent(value, prefix=' ' * 8, predicate=lambda line: True)
+            .lstrip()
+            .splitlines()
+        )
+        return f'{name}: {folded}{self.linesep}'
+
+
 class Message(email.message.Message):
+    r"""
+    Specialized Message subclass to handle metadata naturally.
+
+    Reads values that may have newlines in them and converts the
+    payload to the Description.
+
+    >>> msg_text = textwrap.dedent('''
+    ...     Name: Foo
+    ...     Version: 3.0
+    ...     License: blah
+    ...             de-blah
+    ...     <BLANKLINE>
+    ...     First line of description.
+    ...     Second line of description.
+    ...     <BLANKLINE>
+    ...     Fourth line!
+    ...     ''').lstrip().replace('<BLANKLINE>', '')
+    >>> msg = Message(email.message_from_string(msg_text))
+    >>> msg['Description']
+    'First line of description.\nSecond line of description.\n\nFourth line!\n'
+
+    Message should render even if values contain newlines.
+
+    >>> print(msg)
+    Name: Foo
+    Version: 3.0
+    License: blah
+            de-blah
+    Description: First line of description.
+            Second line of description.
+    <BLANKLINE>
+            Fourth line!
+    <BLANKLINE>
+    <BLANKLINE>
+    """
+
     multiple_use_keys = set(
         map(
             FoldedCase,
@@ -57,15 +104,20 @@ def __getitem__(self, item):
     def _repair_headers(self):
         def redent(value):
             "Correct for RFC822 indentation"
-            if not value or '\n' not in value:
+            indent = ' ' * 8
+            if not value or '\n' + indent not in value:
                 return value
-            return textwrap.dedent(' ' * 8 + value)
+            return textwrap.dedent(indent + value)
 
         headers = [(key, redent(value)) for key, value in vars(self)['_headers']]
         if self._payload:
             headers.append(('Description', self.get_payload()))
+            self.set_payload('')
         return headers
 
+    def as_string(self):
+        return super().as_string(policy=RawPolicy())
+
     @property
     def json(self):
         """

Lib/importlib/metadata/_adapters.py

@@ -1,4 +1,5 @@
 import collections
+import typing
 
 
 # from jaraco.collections 3.3
@@ -24,7 +25,10 @@ def freeze(self):
         self._frozen = lambda key: self.default_factory()
 
 
-class Pair(collections.namedtuple('Pair', 'name value')):
+class Pair(typing.NamedTuple):
+    name: str
+    value: str
+
     @classmethod
     def parse(cls, text):
         return cls(*map(str.strip, text.split("=", 1)))

Lib/importlib/metadata/_collections.py

@@ -1,5 +1,5 @@
-import types
 import functools
+import types
 
 
 # from jaraco.functools 3.3

Lib/importlib/metadata/_functools.py

@@ -1,9 +1,13 @@
 from __future__ import annotations
 
 import os
-from typing import Protocol
-from typing import Any, Dict, Iterator, List, Optional, TypeVar, Union, overload
-
+from collections.abc import Iterator
+from typing import (
+    Any,
+    Protocol,
+    TypeVar,
+    overload,
+)
 
 _T = TypeVar("_T")
 
@@ -20,25 +24,25 @@ def __iter__(self) -> Iterator[str]: ...  # pragma: no cover
     @overload
     def get(
         self, name: str, failobj: None = None
-    ) -> Optional[str]: ...  # pragma: no cover
+    ) -> str | None: ...  # pragma: no cover
 
     @overload
-    def get(self, name: str, failobj: _T) -> Union[str, _T]: ...  # pragma: no cover
+    def get(self, name: str, failobj: _T) -> str | _T: ...  # pragma: no cover
 
     # overload per python/importlib_metadata#435
     @overload
     def get_all(
         self, name: str, failobj: None = None
-    ) -> Optional[List[Any]]: ...  # pragma: no cover
+    ) -> list[Any] | None: ...  # pragma: no cover
 
     @overload
-    def get_all(self, name: str, failobj: _T) -> Union[List[Any], _T]:
+    def get_all(self, name: str, failobj: _T) -> list[Any] | _T:
         """
         Return all values associated with a possibly multi-valued key.
         """
 
     @property
-    def json(self) -> Dict[str, Union[str, List[str]]]:
+    def json(self) -> dict[str, str | list[str]]:
         """
         A JSON-compatible form of the metadata.
         """
@@ -50,11 +54,11 @@ class SimplePath(Protocol):
     """
 
     def joinpath(
-        self, other: Union[str, os.PathLike[str]]
+        self, other: str | os.PathLike[str]
     ) -> SimplePath: ...  # pragma: no cover
 
     def __truediv__(
-        self, other: Union[str, os.PathLike[str]]
+        self, other: str | os.PathLike[str]
     ) -> SimplePath: ...  # pragma: no cover
 
     @property

Lib/importlib/metadata/_meta.py

@@ -0,0 +1,15 @@
+import functools
+import typing
+
+from ._meta import PackageMetadata
+
+md_none = functools.partial(typing.cast, PackageMetadata)
+"""
+Suppress type errors for optional metadata.
+
+Although Distribution.metadata can return None when metadata is corrupt
+and thus None, allow callers to assume it's not None and crash if
+that's the case.
+
+# python/importlib_metadata#493
+"""

Lib/importlib/metadata/_typing.py

@@ -1,9 +1,14 @@
-# from jaraco.path 3.7
+# from jaraco.path 3.7.2
+
+from __future__ import annotations
 
 import functools
 import pathlib
-from typing import Dict, Protocol, Union
-from typing import runtime_checkable
+from collections.abc import Mapping
+from typing import TYPE_CHECKING, Protocol, Union, runtime_checkable
+
+if TYPE_CHECKING:
+    from typing_extensions import Self
 
 
 class Symlink(str):
@@ -12,29 +17,25 @@ class Symlink(str):
     """
 
 
-FilesSpec = Dict[str, Union[str, bytes, Symlink, 'FilesSpec']]  # type: ignore
+FilesSpec = Mapping[str, Union[str, bytes, Symlink, 'FilesSpec']]
 
 
 @runtime_checkable
 class TreeMaker(Protocol):
-    def __truediv__(self, *args, **kwargs): ...  # pragma: no cover
-
-    def mkdir(self, **kwargs): ...  # pragma: no cover
-
-    def write_text(self, content, **kwargs): ...  # pragma: no cover
-
-    def write_bytes(self, content): ...  # pragma: no cover
-
-    def symlink_to(self, target): ...  # pragma: no cover
+    def __truediv__(self, other, /) -> Self: ...
+    def mkdir(self, *, exist_ok) -> object: ...
+    def write_text(self, content, /, *, encoding) -> object: ...
+    def write_bytes(self, content, /) -> object: ...
+    def symlink_to(self, target, /) -> object: ...
 
 
-def _ensure_tree_maker(obj: Union[str, TreeMaker]) -> TreeMaker:
-    return obj if isinstance(obj, TreeMaker) else pathlib.Path(obj)  # type: ignore
+def _ensure_tree_maker(obj: str | TreeMaker) -> TreeMaker:
+    return obj if isinstance(obj, TreeMaker) else pathlib.Path(obj)
 
 
 def build(
     spec: FilesSpec,
-    prefix: Union[str, TreeMaker] = pathlib.Path(),  # type: ignore
+    prefix: str | TreeMaker = pathlib.Path(),
 ):
     """
     Build a set of files/directories, as described by the spec.
@@ -66,23 +67,24 @@ def build(
 
 
 @functools.singledispatch
-def create(content: Union[str, bytes, FilesSpec], path):
+def create(content: str | bytes | FilesSpec, path: TreeMaker) -> None:
     path.mkdir(exist_ok=True)
-    build(content, prefix=path)  # type: ignore
+    # Mypy only looks at the signature of the main singledispatch method. So it must contain the complete Union
+    build(content, prefix=path)  # type: ignore[arg-type] # python/mypy#11727
 
 
 @create.register
-def _(content: bytes, path):
+def _(content: bytes, path: TreeMaker) -> None:
     path.write_bytes(content)
 
 
 @create.register
-def _(content: str, path):
+def _(content: str, path: TreeMaker) -> None:
     path.write_text(content, encoding='utf-8')
 
 
 @create.register
-def _(content: Symlink, path):
+def _(content: Symlink, path: TreeMaker) -> None:
     path.symlink_to(content)
 
 

Lib/test/test_importlib/metadata/_path.py

@@ -1,11 +1,11 @@
-import sys
+import contextlib
 import copy
+import functools
 import json
-import shutil
 import pathlib
+import shutil
+import sys
 import textwrap
-import functools
-import contextlib
 
 from test.support import import_helper
 from test.support import os_helper
@@ -14,14 +14,10 @@
 from . import _path
 from ._path import FilesSpec
 
-
-try:
-    from importlib import resources  # type: ignore
-
-    getattr(resources, 'files')
-    getattr(resources, 'as_file')
-except (ImportError, AttributeError):
-    import importlib_resources as resources  # type: ignore
+if sys.version_info >= (3, 9):
+    from importlib import resources
+else:
+    import importlib_resources as resources
 
 
 @contextlib.contextmanager

Lib/test/test_importlib/metadata/fixtures.py

@@ -1,9 +1,8 @@
+import importlib
 import re
 import textwrap
 import unittest
-import importlib
 
-from . import fixtures
 from importlib.metadata import (
     Distribution,
     PackageNotFoundError,
@@ -15,6 +14,8 @@
     version,
 )
 
+from . import fixtures
+
 
 class APITests(
     fixtures.EggInfoPkg,

Lib/test/test_importlib/metadata/test_api.py

@@ -1,17 +1,14 @@
-import re
+import importlib
 import pickle
+import re
 import unittest
-import importlib
-import importlib.metadata
 from test.support import os_helper
 
 try:
     import pyfakefs.fake_filesystem_unittest as ffs
 except ImportError:
     from .stubs import fake_filesystem_unittest as ffs
 
-from . import fixtures
-from ._path import Symlink
 from importlib.metadata import (
     Distribution,
     EntryPoint,
@@ -24,6 +21,9 @@
     version,
 )
 
+from . import fixtures
+from ._path import Symlink
+
 
 class BasicTests(fixtures.DistInfoPkg, unittest.TestCase):
     version_pattern = r'\d+\.\d+(\.\d)?'
@@ -157,6 +157,16 @@ def test_valid_dists_preferred(self):
         dist = Distribution.from_name('foo')
         assert dist.version == "1.0"
 
+    def test_missing_metadata(self):
+        """
+        Dists with a missing metadata file should return None.
+
+        Ref python/importlib_metadata#493.
+        """
+        fixtures.build_files(self.make_pkg('foo-4.3', files={}), self.site_dir)
+        assert Distribution.from_name('foo').metadata is None
+        assert metadata('foo') is None
+
 
 class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
     @staticmethod