fix: don't count or record entry points that register() declined

changelog/804.bugfix.rst

@@ -0,0 +1 @@
+:meth:`PluginManager.load_setuptools_entrypoints() <pluggy.PluginManager.load_setuptools_entrypoints>` no longer counts, or records the distribution of, an entry point whose plugin was not registered: a plugin which loads to ``None``, or one which a :class:`~pluggy.PluginManager` subclass declines to register, as pytest's does for plugins whose names were merged into ``pytest``. With such a plugin installed, listing plugins through :meth:`~pluggy.PluginManager.list_plugin_distinfo` and :meth:`~pluggy.PluginManager.list_plugin_distributions` raised :exc:`KeyError`.

src/pluggy/_manager.py

@@ -517,8 +517,16 @@ def load_setuptools_entrypoints(self, group: str, name: str | None = None) -> in
                 ):
                     continue
                 plugin = ep.load()
-                self.register(plugin, name=ep.name)
-                self._name2dist[ep.name] = dist
+                registered_name = self.register(plugin, name=ep.name)
+                if registered_name is None:
+                    # register() declined to register this plugin: it returns
+                    # None for a None plugin, and a PluginManager subclass may
+                    # do the same (pytest's ignores deprecated plugin names).
+                    # Nothing was registered, so nothing may be counted or
+                    # remembered -- list_plugin_distributions() looks the names
+                    # up in the plugin registry.
+                    continue
+                self._name2dist[registered_name] = dist
                 count += 1
         return count
 

testing/test_pluginmanager.py

@@ -993,6 +993,49 @@ class Distribution:
     assert pm.list_plugin_distributions() == [(a, dist)]
 
 
+def test_load_setuptools_declined_plugin_is_not_recorded(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """An entry point whose plugin ``register()`` declines was not loaded.
+
+    ``register()`` returns ``None`` when it registers nothing: for a ``None``
+    plugin, and for a ``PluginManager`` subclass which declines one, as
+    pytest's does for deprecated plugin names. Such an entry point must not be
+    counted, and must not be remembered for
+    :meth:`~pluggy.PluginManager.list_plugin_distinfo` and
+    :meth:`~pluggy.PluginManager.list_plugin_distributions`, which look the
+    recorded names up in the plugin registry.
+    """
+
+    class EntryPoint:
+        group = "hello"
+
+        def __init__(self, name: str, target: object) -> None:
+            self.name = name
+            self._target = target
+
+        def load(self) -> object:
+            return self._target
+
+    class Distribution:
+        entry_points = (EntryPoint("null", None), EntryPoint("declined", object()))
+
+    dist = cast(importlib.metadata.Distribution, Distribution())
+    monkeypatch.setattr(importlib.metadata, "distributions", lambda: (dist,))
+
+    class DecliningPluginManager(PluginManager):
+        def register(self, plugin: object, name: str | None = None) -> str | None:
+            if name == "declined":
+                return None
+            return super().register(plugin, name=name)
+
+    pm = DecliningPluginManager("example")
+    assert pm.load_setuptools_entrypoints("hello") == 0
+    assert pm.list_name_plugin() == []
+    assert pm.list_plugin_distributions() == []
+    assert pm.list_plugin_distinfo() == []
+
+
 def test_add_tracefuncs(he_pm: PluginManager) -> None:
     out: list[Any] = []