fix(manager): drop the distinfo entry when a plugin is unregistered

changelog/763.bugfix.rst

@@ -0,0 +1 @@
+Fix a stale entry in :meth:`~pluggy.PluginManager.list_name_plugin` when a plugin is unregistered with :meth:`~pluggy.PluginManager.unregister`: the distribution metadata recorded by :meth:`~pluggy.PluginManager.register` is now dropped together with the plugin, so re-registering a different plugin under the same name no longer reports the old distribution.

src/pluggy/_manager.py

@@ -320,6 +320,14 @@ def unregister(
         if self._name2plugin.get(name) is not None:
             del self._name2plugin[name]
 
+        # Drop the entry-point bookkeeping for this plugin as well. Leaving it in
+        # place made list_plugin_distinfo()/list_plugin_distributions() keep
+        # reporting an unregistered plugin, and a later re-registration appended a
+        # second entry for the same plugin.
+        self._plugin_distinfo[:] = [
+            (p, dist) for p, dist in self._plugin_distinfo if p is not plugin
+        ]
+
         return plugin
 
     def set_blocked(self, name: str) -> None:

testing/test_unregister_distinfo.py

@@ -0,0 +1,93 @@
+"""Regression coverage for pluggy issue #763.
+
+``PluginManager.unregister`` removed the plugin from the hook callers and from
+``_name2plugin`` but left its ``_plugin_distinfo`` entry behind. A plugin loaded
+through entry points therefore kept appearing in ``list_plugin_distinfo()`` and
+``list_plugin_distributions()`` after being unregistered, and re-registering it
+appended a second entry for the same plugin.
+"""
+
+from __future__ import annotations
+
+import importlib.metadata
+from typing import cast
+
+import pytest
+
+from pluggy import PluginManager
+
+
+def _install_entrypoint_dist(monkeypatch: pytest.MonkeyPatch, holder: dict) -> None:
+    """Make importlib.metadata report one distribution with a single entry point."""
+
+    class EntryPoint:
+        name = "myname"
+        group = "hello"
+        value = "myname:foo"
+
+        def load(self):
+            holder["loads"] = holder.get("loads", 0) + 1
+            return holder["plugin"]
+
+    class Distribution:
+        entry_points = (EntryPoint(),)
+
+    dist = cast(importlib.metadata.Distribution, Distribution())
+    monkeypatch.setattr(importlib.metadata, "distributions", lambda: (dist,))
+    holder["dist"] = dist
+
+
+def test_unregister_drops_the_plugin_distinfo_entry(
+    monkeypatch: pytest.MonkeyPatch, pm: PluginManager
+) -> None:
+    """An unregistered entry-point plugin must not be listed any more."""
+    holder: dict = {"plugin": type("PseudoPlugin", (), {})()}
+    _install_entrypoint_dist(monkeypatch, holder)
+
+    assert pm.load_setuptools_entrypoints("hello") == 1
+    plugin = pm.get_plugin("myname")
+    assert plugin is holder["plugin"]
+    assert len(pm.list_plugin_distributions()) == 1
+    assert len(pm.list_plugin_distinfo()) == 1
+
+    assert pm.unregister(name="myname") is plugin
+
+    assert pm.get_plugin("myname") is None
+    assert pm.list_plugin_distributions() == []
+    assert pm.list_plugin_distinfo() == []
+
+
+def test_unregister_then_reregister_does_not_duplicate_distinfo(
+    monkeypatch: pytest.MonkeyPatch, pm: PluginManager
+) -> None:
+    """Re-registering must not leave two entries for the same plugin."""
+    holder: dict = {"plugin": type("PseudoPlugin", (), {})()}
+    _install_entrypoint_dist(monkeypatch, holder)
+
+    assert pm.load_setuptools_entrypoints("hello") == 1
+    plugin = pm.get_plugin("myname")
+    pm.unregister(name="myname")
+
+    pm.register(plugin, name="myname")
+    assert pm.list_plugin_distributions() == []
+    assert pm.list_plugin_distinfo() == []
+
+    # Reloading from the entry point re-appends exactly one entry.
+    assert pm.unregister(name="myname") is plugin
+    assert pm.load_setuptools_entrypoints("hello") == 1
+    assert pm.list_plugin_distributions() == [(plugin, holder["dist"])]
+
+
+def test_unregister_by_plugin_object_also_drops_distinfo(
+    monkeypatch: pytest.MonkeyPatch, pm: PluginManager
+) -> None:
+    """The plugin-object form of unregister clears the bookkeeping too."""
+    holder: dict = {"plugin": type("PseudoPlugin", (), {})()}
+    _install_entrypoint_dist(monkeypatch, holder)
+
+    assert pm.load_setuptools_entrypoints("hello") == 1
+    plugin = pm.get_plugin("myname")
+
+    assert pm.unregister(plugin=plugin) is plugin
+    assert pm.list_plugin_distributions() == []
+    assert pm.list_plugin_distinfo() == []