Fix Union entry point discovery on Python <3.12

.changelog/_unreleased.toml

@@ -0,0 +1,6 @@
+[[entries]]
+id = "67afd70b-b66e-4aeb-ab30-becf3f121681"
+type = "fix"
+description = "Fix `Union` entry point discovery by no longer passing the `group` keyword to `importlib.metadata.entry_points()`, drop the deprecated `pkg_resources` fallback (`importlib.metadata` is used on all supported Python versions), and remove the now-unused `setuptools` runtime dependency on Python <3.9"
+author = "@NiklasRosenstein"
+pr = "https://github.com/NiklasRosenstein/python-databind/pull/84"

databind/pyproject.toml

@@ -14,7 +14,6 @@ dependencies = [
     "Deprecated>=1.2.12,<2",
     "nr-date>=2.0.0,<3",
     "nr-stream>=1.0.0,<2",
-    "setuptools>=40.8.0,<82; python_version < '3.9'",
     "typeapi>=2.0.1,<3",
     "typing-extensions>=3.10.0,<5",
 ]

databind/src/databind/core/tests/union_test.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+import typing as t
+
+from pytest import MonkeyPatch
+
+import databind.core.union as union_module
+
+
+def test_iter_entry_points_uses_select_api_without_call_arguments(monkeypatch: MonkeyPatch) -> None:
+    result = [object(), object()]
+
+    class EntryPoints:
+        def __init__(self) -> None:
+            self.selected_group: str | None = None
+
+        def select(self, *, group: str) -> list[object]:
+            self.selected_group = group
+            return result
+
+    eps = EntryPoints()
+
+    def fake_entry_points(*args: object, **kwargs: object) -> object:
+        assert args == ()
+        assert kwargs == {}
+        return eps
+
+    monkeypatch.setattr(union_module, "entry_points", fake_entry_points)
+
+    assert list(union_module.iter_entry_points("my.group")) == t.cast(t.Any, result)
+    assert eps.selected_group == "my.group"
+
+
+def test_iter_entry_points_falls_back_to_mapping_result(monkeypatch: MonkeyPatch) -> None:
+    result = [object(), object()]
+
+    def fake_entry_points(*args: object, **kwargs: object) -> object:
+        assert args == ()
+        assert kwargs == {}
+        return {"my.group": result}
+
+    monkeypatch.setattr(union_module, "entry_points", fake_entry_points)
+
+    assert list(union_module.iter_entry_points("my.group")) == t.cast(t.Any, result)
+    assert list(union_module.iter_entry_points("missing")) == []

databind/src/databind/core/union.py

@@ -3,21 +3,20 @@
 import abc
 import dataclasses
 import importlib
-import sys
 import types
 import typing as t
+from importlib.metadata import EntryPoint, entry_points
 
 from typeapi import ClassTypeHint, LiteralTypeHint, TypeHint
 
 from databind.core.utils import T
 
-if sys.version_info[:2] < (3, 9):
-    from pkg_resources import EntryPoint, iter_entry_points  # type: ignore[import-not-found,unused-ignore]
-else:
-    from importlib.metadata import EntryPoint, entry_points
 
-    def iter_entry_points(group: str) -> t.Iterator[EntryPoint]:
-        return iter(entry_points(group=group))
+def iter_entry_points(group: str) -> t.Iterator[EntryPoint]:
+    eps = entry_points()
+    if hasattr(eps, "select"):
+        return iter(eps.select(group=group))
+    return iter(eps.get(group, ()))
 
 
 __all__ = ["UnionMembers", "StaticUnionMembers", "EntrypointUnionMembers", "ImportUnionMembers", "ChainUnionMembers"]

pyproject.toml

@@ -25,7 +25,6 @@ dev = [
     "mypy>=1.9.0,<2.0.0",
     "types-dataclasses",
     "types-deprecated",
-    "types-setuptools",
     "types-termcolor",
 ]
 docs = [