[3.10] bpo-44246: Restore compatibility in entry_points (GH-26468)

Lib/importlib/metadata/__init__.py

@@ -204,7 +204,100 @@ def matches(self, **params):
  return all(map(operator.eq, params.values(), attrs))
 
 
-class EntryPoints(tuple):
+class DeprecatedList(list):
+ """
+ Allow an otherwise immutable object to implement mutability
+ for compatibility.
+
+ >>> recwarn = getfixture('recwarn')
+ >>> dl = DeprecatedList(range(3))
+ >>> dl[0] = 1
+ >>> dl.append(3)
+ >>> del dl[3]
+ >>> dl.reverse()
+ >>> dl.sort()
+ >>> dl.extend([4])
+ >>> dl.pop(-1)
+ 4
+ >>> dl.remove(1)
+ >>> dl += [5]
+ >>> dl + [6]
+ [1, 2, 5, 6]
+ >>> dl + (6,)
+ [1, 2, 5, 6]
+ >>> dl.insert(0, 0)
+ >>> dl
+ [0, 1, 2, 5]
+ >>> dl == [0, 1, 2, 5]
+ True
+ >>> dl == (0, 1, 2, 5)
+ True
+ >>> len(recwarn)
+ 1
+ """
+
+ _warn = functools.partial(
+ warnings.warn,
+ "EntryPoints list interface is deprecated. Cast to list if needed.",
+ DeprecationWarning,
+ stacklevel=2,
+ )
+
+ def __setitem__(self, *args, **kwargs):
+ self._warn()
+ return super().__setitem__(*args, **kwargs)
+
+ def __delitem__(self, *args, **kwargs):
+ self._warn()
+ return super().__delitem__(*args, **kwargs)
+
+ def append(self, *args, **kwargs):
+ self._warn()
+ return super().append(*args, **kwargs)
+
+ def reverse(self, *args, **kwargs):
+ self._warn()
+ return super().reverse(*args, **kwargs)
+
+ def extend(self, *args, **kwargs):
+ self._warn()
+ return super().extend(*args, **kwargs)
+
+ def pop(self, *args, **kwargs):
+ self._warn()
+ return super().pop(*args, **kwargs)
+
+ def remove(self, *args, **kwargs):
+ self._warn()
+ return super().remove(*args, **kwargs)
+
+ def __iadd__(self, *args, **kwargs):
+ self._warn()
+ return super().__iadd__(*args, **kwargs)
+
+ def __add__(self, other):
+ if not isinstance(other, tuple):
+ self._warn()
+ other = tuple(other)
+ return self.__class__(tuple(self) + other)
+
+ def insert(self, *args, **kwargs):
+ self._warn()
+ return super().insert(*args, **kwargs)
+
+ def sort(self, *args, **kwargs):
+ self._warn()
+ return super().sort(*args, **kwargs)
+
+ def __eq__(self, other):
+ if not isinstance(other, tuple):
+ self._warn()
+ other = tuple(other)
+
+ return tuple(self).__eq__(other)
+
+
+class EntryPoints(DeprecatedList):
  """
  An immutable collection of selectable EntryPoint objects.
  """
@@ -215,6 +308,14 @@ def __getitem__(self, name): # -> EntryPoint:
  """
  Get the EntryPoint in self matching name.
  """
+ if isinstance(name, int):
+ warnings.warn(
+ "Accessing entry points by index is deprecated. "
+ "Cast to tuple if needed.",
+ DeprecationWarning,
+ stacklevel=2,
+ )
+ return super().__getitem__(name)
  try:
  return next(iter(self.select(name=name)))
  except StopIteration:

Lib/test/test_importlib/test_metadata_api.py

@@ -130,6 +130,22 @@ def test_entry_points_dict_construction(self):
  assert expected.category is DeprecationWarning
  assert "Construction of dict of EntryPoints is deprecated" in str(expected)
 
+ def test_entry_points_by_index(self):
+ """
+ Prior versions of Distribution.entry_points would return a
+ tuple that allowed access by index.
+ Capture this now deprecated use-case
+ See python/importlib_metadata#300 and bpo-44246.
+ """
+ eps = distribution('distinfo-pkg').entry_points
+ with warnings.catch_warnings(record=True) as caught:
+ eps[0]
+
+ # check warning
+ expected = next(iter(caught))
+ assert expected.category is DeprecationWarning
+ assert "Accessing entry points by index is deprecated" in str(expected)
+
  def test_entry_points_groups_getitem(self):
  # Prior versions of entry_points() returned a dict. Ensure
  # that callers using '.__getitem__()' are supported but warned to

Misc/NEWS.d/next/Library/2021-05-31-11-34-56.bpo-44246.yHAkF0.rst

@@ -0,0 +1,7 @@
+In ``importlib.metadata``, restore compatibility in the result from
+``Distribution.entry_points`` (``EntryPoints``) to honor expectations in
+older implementations and issuing deprecation warnings for these cases: A. ``EntryPoints`` objects are once again mutable, allowing for ``sort()``
+and other list-based mutation operations. Avoid deprecation warnings by
+casting to a mutable sequence (e.g. ``list(dist.entry_points).sort()``). B. ``EntryPoints`` results once again allow for access by index. To avoid
+deprecation warnings, cast the result to a Sequence first (e.g.
+``tuple(dist.entry_points)[0]``).