bpo-39022, bpo-38594: Sync with importlib_metadata 1.3 (GH-17568)

* bpo-39022, bpo-38594: Sync with importlib_metadata 1.3 including improved docs for custom finders and better serialization support in EntryPoints.

* 📜🤖 Added by blurb_it.

* Correct module reference

2 files changed, 55 insertions, 1 deletions

diff --git a/Lib/importlib/metadata.py b/Lib/importlib/metadata.py
index 8cb45ec..53f9fb5 100644
--- a/Lib/importlib/metadata.py
+++ b/Lib/importlib/metadata.py
@@ -37,7 +37,8 @@ class PackageNotFoundError(ModuleNotFoundError):
     """The package was not found."""
 
 
-class EntryPoint(collections.namedtuple('EntryPointBase', 'name value group')):
+class EntryPoint(
+        collections.namedtuple('EntryPointBase', 'name value group')):
     """An entry point as defined by Python packaging conventions.
 
     See `the packaging docs on entry points
@@ -107,6 +108,12 @@ class EntryPoint(collections.namedtuple('EntryPointBase', 'name value group')):
         """
         return iter((self.name, self))
 
+    def __reduce__(self):
+        return (
+            self.__class__,
+            (self.name, self.value, self.group),
+            )
+
 
 class PackagePath(pathlib.PurePosixPath):
     """A reference to a path in a package"""
@@ -334,10 +341,21 @@ class DistributionFinder(MetaPathFinder):
     """
 
     class Context:
+        """
+        Keyword arguments presented by the caller to
+        ``distributions()`` or ``Distribution.discover()``
+        to narrow the scope of a search for distributions
+        in all DistributionFinders.
+
+        Each DistributionFinder may expect any parameters
+        and should attempt to honor the canonical
+        parameters defined below when appropriate.
+        """
 
         name = None
         """
         Specific name for which a distribution finder should match.
+        A name of ``None`` matches all distributions.
         """
 
         def __init__(self, **kwargs):
@@ -347,6 +365,9 @@ class DistributionFinder(MetaPathFinder):
         def path(self):
             """
             The path that a distribution finder should search.
+
+            Typically refers to Python package paths and defaults
+            to ``sys.path``.
             """
             return vars(self).get('path', sys.path)
 
diff --git a/Lib/test/test_importlib/test_main.py b/Lib/test/test_importlib/test_main.py
index 4d5b127..c5f1dbb 100644
--- a/Lib/test/test_importlib/test_main.py
+++ b/Lib/test/test_importlib/test_main.py
@@ -1,6 +1,8 @@
 # coding: utf-8
 
 import re
+import json
+import pickle
 import textwrap
 import unittest
 import importlib.metadata
@@ -181,3 +183,34 @@ class DirectoryTest(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
         with self.add_sys_path(egg):
             with self.assertRaises(PackageNotFoundError):
                 version('foo')
+
+
+class TestEntryPoints(unittest.TestCase):
+    def __init__(self, *args):
+        super(TestEntryPoints, self).__init__(*args)
+        self.ep = importlib.metadata.EntryPoint('name', 'value', 'group')
+
+    def test_entry_point_pickleable(self):
+        revived = pickle.loads(pickle.dumps(self.ep))
+        assert revived == self.ep
+
+    def test_immutable(self):
+        """EntryPoints should be immutable"""
+        with self.assertRaises(AttributeError):
+            self.ep.name = 'badactor'
+
+    def test_repr(self):
+        assert 'EntryPoint' in repr(self.ep)
+        assert 'name=' in repr(self.ep)
+        assert "'name'" in repr(self.ep)
+
+    def test_hashable(self):
+        """EntryPoints should be hashable"""
+        hash(self.ep)
+
+    def test_json_dump(self):
+        """
+        json should not expect to be able to dump an EntryPoint
+        """
+        with self.assertRaises(Exception):
+            json.dumps(self.ep)