add coverage for optional hook validation and error cases

Author: RonnyPfannschmidt

src/pluggy/_manager.py

@@ -378,15 +378,16 @@ def check_pending(self) -> None:
         hook specification are optional, otherwise raise
         :exc:`PluginValidationError`."""
         for name in self.hook.__dict__:
-            if name[0] != "_":
-                hook: HookCaller = getattr(self.hook, name)
-                if not hook.has_spec():
-                    for hookimpl in hook.get_hookimpls():
-                        if not hookimpl.optionalhook:
-                            raise PluginValidationError(
-                                hookimpl.plugin,
-                                f"unknown hook {name!r} in plugin {hookimpl.plugin!r}",
-                            )
+            if name[0] == "_":
+                continue
+            hook: HookCaller = getattr(self.hook, name)
+            if not hook.has_spec():
+                for hookimpl in hook.get_hookimpls():
+                    if not hookimpl.optionalhook:
+                        raise PluginValidationError(
+                            hookimpl.plugin,
+                            f"unknown hook {name!r} in plugin {hookimpl.plugin!r}",
+                        )
 
     def load_setuptools_entrypoints(self, group: str, name: str | None = None) -> int:
         """Load modules from querying the specified setuptools ``group``.

testing/test_pluginmanager.py

@@ -771,6 +771,31 @@ def configure(self) -> int:
         assert result == [4, 5, 3, 2, 1, 6]
 
 
+def test_check_pending_skips_underscore(pm: PluginManager) -> None:
+    # todo: determine what we want to do with the namespace
+    class Plugin:
+        @hookimpl
+        def _problem(self):
+            pass
+
+    pm.register(Plugin())
+    pm.hook._problem()
+    pm.check_pending()
+
+
+def test_check_pending_optionalhook(
+    pm: PluginManager,
+) -> None:
+    class Plugin:
+        @hookimpl(optionalhook=True)
+        def a_hook(self, param):
+            pass
+
+    pm.register(Plugin())
+    pm.hook.a_hook(param=1)
+    pm.check_pending()
+
+
 def test_check_pending_nonspec_hook(
     pm: PluginManager,
 ) -> None:
@@ -784,3 +809,8 @@ def a_hook(self, param):
     pm.register(Plugin())
     with pytest.raises(HookCallError, match="hook call must provide argument 'param'"):
         pm.hook.a_hook()
+
+    with pytest.raises(
+        PluginValidationError, match="unknown hook 'a_hook' in plugin .*"
+    ):
+        pm.check_pending()