Avoid triggering @property methods on plugins when looking for hookimpls during registration

src/pluggy/_manager.py

@@ -46,6 +46,17 @@
     )
 
 
+def _attr_is_property(obj: object, name: str) -> bool:
+    """Check if a given attr is a @property on a module, class, or object"""
+    if inspect.ismodule(obj):
+        return False  # modules can never have @property methods
+
+    base_class = obj if inspect.isclass(obj) else type(obj)
+    if isinstance(getattr(base_class, name, None), property):
+        return True
+    return False
+
+
 class PluginValidationError(Exception):
     """Plugin failed validation.
 
@@ -181,7 +192,20 @@
         customize how hook implementation are picked up. By default, returns the
         options for items decorated with :class:`HookimplMarker`.
         """
-        method: object = getattr(plugin, name)
+
+        if _attr_is_property(plugin, name):
+            # @property methods can have side effects, and are never hookimpls
+            return None
+
+        method: object
+        try:
+            method = getattr(plugin, name)
+        except AttributeError:
+            # AttributeError: '__signature__' attribute of 'plugin' is class-only
+            # can be raised when trying to access some descriptor/proxied fields
+            # https://github.com/pytest-dev/pluggy/pull/536#discussion_r1786431032
+            return None
+
         if not inspect.isroutine(method):
             return None
         try:
@@ -286,7 +310,18 @@
         customize how hook specifications are picked up. By default, returns the
         options for items decorated with :class:`HookspecMarker`.
         """
-        method = getattr(module_or_class, name)
+        if _attr_is_property(module_or_class, name):
+            # @property methods can have side effects, and are never hookspecs
+            return None
+
+        method: object
+        try:
+            method = getattr(module_or_class, name)
+        except AttributeError:
+            # AttributeError: '__signature__' attribute of <m_or_c> is class-only
+            # can be raised when trying to access some descriptor/proxied fields
+            # https://github.com/pytest-dev/pluggy/pull/536#discussion_r1786431032
+            return None
         opts: HookspecOpts | None = getattr(method, self.project_name + "_spec", None)
         return opts
 

testing/test_pluginmanager.py

@@ -123,6 +123,23 @@ class A:
     assert pm.register(A(), "somename")
 
 
+def test_register_ignores_properties(he_pm: PluginManager) -> None:
+    class ClassWithProperties:
+        property_was_executed: bool = False
+
+        @property
+        def some_func(self):
+            self.property_was_executed = True  # pragma: no cover
+            return None  # pragma: no cover
+
+    # test registering it as a class
+    he_pm.register(ClassWithProperties)
+    # test registering it as an instance
+    test_plugin = ClassWithProperties()
+    he_pm.register(test_plugin)
+    assert not test_plugin.property_was_executed
+
+
 def test_register_mismatch_method(he_pm: PluginManager) -> None:
     class hello:
         @hookimpl