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

src/pluggy/_manager.py

@@ -181,7 +181,26 @@
         customize how hook implementation are picked up. By default, returns the
         options for items decorated with :class:`HookimplMarker`.
         """
-        method: object = getattr(plugin, name)
+
+        # IMPORTANT: @property methods can have side effects, and are never hookimpl
+        # if attr is a property, skip it in advance
+        plugin_class = plugin if inspect.isclass(plugin) else type(plugin)
+        if isinstance(getattr(plugin_class, name, None), property):
+            return None
+
+        # pydantic model fields are like attrs and also can never be hookimpls
+        plugin_is_pydantic_obj = hasattr(plugin, "__pydantic_core_schema__")
+        if plugin_is_pydantic_obj and name in getattr(plugin, "model_fields", {}):
+            return None
+
+        method: object
+        try:
+            method = getattr(plugin, name)
+        except AttributeError:
+            # AttributeError: '__signature__' attribute of 'Plugin' is class-only
+            # can happen for some special objects (e.g. proxies, pydantic, etc.)
+            method = getattr(type(plugin), name)  # use class sig instead
+
         if not inspect.isroutine(method):
             return None
         try:

testing/test_pluginmanager.py

@@ -4,6 +4,7 @@
 
 import importlib.metadata
 from typing import Any
+from typing import Dict
 from typing import List
 
 import pytest
@@ -123,6 +124,36 @@
     assert pm.register(A(), "somename")
 
 
+def test_register_skips_properties(he_pm: PluginManager) -> None:
+    class ClassWithProperties:
+        property_was_executed: bool = False
+
+        @property
+        def some_func(self):
+            self.property_was_executed = True
+            return None
+
+    test_plugin = ClassWithProperties()
+    he_pm.register(test_plugin)
+    assert not test_plugin.property_was_executed
+
+
+def test_register_skips_pydantic_fields(he_pm: PluginManager) -> None:
+    class PydanticModelClass:
+        # stub to make object look like a pydantic model
+        model_fields: Dict[str, bool] = {"some_attr": True}
+
+        def __pydantic_core_schema__(self): ...
+
+        @hookimpl
+        def some_attr(self): ...
+
+    test_plugin = PydanticModelClass()
+    he_pm.register(test_plugin)
+    with pytest.raises(AttributeError):
+        he_pm.hook.some_attr.get_hookimpls()
+
+
 def test_register_mismatch_method(he_pm: PluginManager) -> None:
     class hello:
         @hookimpl