Commit importlib.metadata as found at 6f8bd81d

Lib/importlib/metadata/_hooks.py

@@ -0,0 +1,138 @@
+import re
+import sys
+import itertools
+
+from . import zipp
+from .api import Distribution
+from .abc import DistributionFinder
+from contextlib import suppress
+from pathlib import Path
+
+
+def install(cls):
+    """Class decorator for installation on sys.meta_path."""
+    sys.meta_path.append(cls())
+    return cls
+
+
+class NullFinder(DistributionFinder):
+    """
+    A "Finder" (aka "MetaClassFinder") that never finds any modules,
+    but may find distributions.
+    """
+    @staticmethod
+    def find_spec(*args, **kwargs):
+        return None
+
+
+@install
+class MetadataPathFinder(NullFinder):
+    """A degenerate finder for distribution packages on the file system.
+
+    This finder supplies only a find_distributions() method for versions
+    of Python that do not have a PathFinder find_distributions().
+    """
+    search_template = r'{pattern}(-.*)?\.(dist|egg)-info'
+
+    def find_distributions(self, name=None, path=None):
+        """Return an iterable of all Distribution instances capable of
+        loading the metadata for packages matching the name
+        (or all names if not supplied) along the paths in the list
+        of directories ``path`` (defaults to sys.path).
+        """
+        if path is None:
+            path = sys.path
+        pattern = '.*' if name is None else re.escape(name)
+        found = self._search_paths(pattern, path)
+        return map(PathDistribution, found)
+
+    @classmethod
+    def _search_paths(cls, pattern, paths):
+        """
+        Find metadata directories in paths heuristically.
+        """
+        return itertools.chain.from_iterable(
+            cls._search_path(path, pattern)
+            for path in map(Path, paths)
+            )
+
+    @classmethod
+    def _search_path(cls, root, pattern):
+        if not root.is_dir():
+            return ()
+        normalized = pattern.replace('-', '_')
+        return (
+            item
+            for item in root.iterdir()
+            if item.is_dir()
+            and re.match(
+                cls.search_template.format(pattern=normalized),
+                str(item.name),
+                flags=re.IGNORECASE,
+                )
+            )
+
+
+class PathDistribution(Distribution):
+    def __init__(self, path):
+        """Construct a distribution from a path to the metadata directory."""
+        self._path = path
+
+    def read_text(self, filename):
+        with suppress(FileNotFoundError):
+            with self._path.joinpath(filename).open(encoding='utf-8') as fp:
+                return fp.read()
+        return None
+    read_text.__doc__ = Distribution.read_text.__doc__
+
+    def locate_file(self, path):
+        return self._path.parent / path
+
+
+@install
+class WheelMetadataFinder(NullFinder):
+    """A degenerate finder for distribution packages in wheels.
+
+    This finder supplies only a find_distributions() method for versions
+    of Python that do not have a PathFinder find_distributions().
+    """
+    search_template = r'{pattern}(-.*)?\.whl'
+
+    def find_distributions(self, name=None, path=None):
+        """Return an iterable of all Distribution instances capable of
+        loading the metadata for packages matching the name
+        (or all names if not supplied) along the paths in the list
+        of directories ``path`` (defaults to sys.path).
+        """
+        if path is None:
+            path = sys.path
+        pattern = '.*' if name is None else re.escape(name)
+        found = self._search_paths(pattern, path)
+        return map(WheelDistribution, found)
+
+    @classmethod
+    def _search_paths(cls, pattern, paths):
+        return (
+            path
+            for path in map(Path, paths)
+            if re.match(
+                cls.search_template.format(pattern=pattern),
+                str(path.name),
+                flags=re.IGNORECASE,
+                )
+            )
+
+
+class WheelDistribution(Distribution):
+    def __init__(self, archive):
+        self._archive = zipp.Path(archive)
+        name, version = archive.name.split('-')[0:2]
+        self._dist_info = '{}-{}.dist-info'.format(name, version)
+
+    def read_text(self, filename):
+        target = self._archive / self._dist_info / filename
+        return target.read_text() if target.exists() else None
+    read_text.__doc__ = Distribution.read_text.__doc__
+
+    def locate_file(self, path):
+        return self._archive / path