Feature/get plugins for hook

pluggy/manager.py

@@ -289,6 +289,11 @@ def get_hookcallers(self, plugin):
         """ get all hook callers for the specified plugin. """
         return self._plugin2hookcallers.get(plugin)
 
+    def get_hookimpl(self, name):
+        """ Return a list of all hook implementations (HookImpl) for a given hook. """
+        hc = getattr(self.hook, name)
+        return hc._wrappers + hc._nonwrappers
+
     def add_hookcall_monitoring(self, before, after):
         """ add before/after tracing functions for all hooks
         and return an undo function which, when called,

testing/test_pluginmanager.py

@@ -384,6 +384,40 @@ class PluginNo(object):
     assert out == [10]
 
 
+def test_get_hookimpl(pm):
+    class Hooks(object):
+        @hookspec
+        def he_method1(self, arg):
+            pass
+
+    pm.add_hookspecs(Hooks)
+
+    class Plugin1(object):
+        @hookimpl
+        def he_method1(self, arg):
+            pass
+
+    class Plugin2(object):
+        @hookimpl
+        def he_method1(self, arg):
+            pass
+
+    class PluginNo(object):
+        pass
+
+    plugin1, plugin2, plugin3 = Plugin1(), Plugin2(), PluginNo()
+    pm.register(plugin1)
+    pm.register(plugin2)
+    pm.register(plugin3)
+
+    hookimpls = pm.get_hookimpl("he_method1")
+    hook_plugins = [hookimpl.plugin for hookimpl in hookimpls]
+
+    assert plugin1 in hook_plugins
+    assert plugin2 in hook_plugins
+    assert plugin3 not in hook_plugins
+
+
 def test_add_hookspecs_nohooks(pm):
     with pytest.raises(ValueError):
         pm.add_hookspecs(10)