Slightly simplify listener registration

beets/plugins.py

@@ -23,7 +23,7 @@ import traceback
 from collections import defaultdict
 from functools import wraps
 from types import GenericAlias
-from typing import TYPE_CHECKING, Any, Callable, Sequence, TypeVar
+from typing import TYPE_CHECKING, Any, ClassVar, TypeVar
 
 import mediafile
 from typing_extensions import ParamSpec
@@ -32,17 +32,14 @@ import beets
 from beets import logging
 
 if TYPE_CHECKING:
-    from beets.event_types import EventType
+    from collections.abc import Callable, Iterable, Sequence
-
-
-if TYPE_CHECKING:
-    from collections.abc import Iterable
 
     from confuse import ConfigView
 
     from beets.dbcore import Query
     from beets.dbcore.db import FieldQueryType
     from beets.dbcore.types import Type
+    from beets.event_types import EventType
     from beets.importer import ImportSession, ImportTask
     from beets.library import Album, Item, Library
     from beets.ui import Subcommand
@@ -58,7 +55,7 @@ if TYPE_CHECKING:
 
     P = ParamSpec("P")
     Ret = TypeVar("Ret", bound=Any)
-    Listener = Callable[..., None]
+    Listener = Callable[..., Any]
     IterF = Callable[P, Iterable[Ret]]
 
 
@@ -105,6 +102,14 @@ class BeetsPlugin(metaclass=abc.ABCMeta):
     the abstract methods defined here.
     """
 
+    _raw_listeners: ClassVar[dict[EventType, list[Listener]]] = defaultdict(
+        list
+    )
+    listeners: ClassVar[dict[EventType, list[Listener]]] = defaultdict(list)
+    template_funcs: TFuncMap[str] | None = None
+    template_fields: TFuncMap[Item] | None = None
+    album_template_fields: TFuncMap[Album] | None = None
+
     name: str
     config: ConfigView
     early_import_stages: list[ImportStageFunc]
@@ -218,25 +223,13 @@ class BeetsPlugin(metaclass=abc.ABCMeta):
         mediafile.MediaFile.add_field(name, descriptor)
         library.Item._media_fields.add(name)
 
-    _raw_listeners: dict[str, list[Listener]] | None = None
+    def register_listener(self, event: EventType, func: Listener) -> None:
-    listeners: dict[str, list[Listener]] | None = None
-
-    def register_listener(self, event: "EventType", func: Listener):
         """Add a function as a listener for the specified event."""
-        wrapped_func = self._set_log_level_and_params(logging.WARNING, func)
+        if func not in self._raw_listeners[event]:
-
+            self._raw_listeners[event].append(func)
-        cls = self.__class__
+            self.listeners[event].append(
-
+                self._set_log_level_and_params(logging.WARNING, func)
-        if cls.listeners is None or cls._raw_listeners is None:
+            )
-            cls._raw_listeners = defaultdict(list)
-            cls.listeners = defaultdict(list)
-        if func not in cls._raw_listeners[event]:
-            cls._raw_listeners[event].append(func)
-            cls.listeners[event].append(wrapped_func)
-
-    template_funcs: TFuncMap[str] | None = None
-    template_fields: TFuncMap[Item] | None = None
-    album_template_fields: TFuncMap[Album] | None = None
 
     @classmethod
     def template_func(cls, name: str) -> Callable[[TFunc[str]], TFunc[str]]:
@@ -383,7 +376,9 @@ def named_queries(model_cls: type[AnyModel]) -> dict[str, FieldQueryType]:
     }
 
 
-def notify_info_yielded(event: str) -> Callable[[IterF[P, Ret]], IterF[P, Ret]]:
+def notify_info_yielded(
+    event: EventType,
+) -> Callable[[IterF[P, Ret]], IterF[P, Ret]]:
     """Makes a generator send the event 'event' every time it yields.
     This decorator is supposed to decorate a generator, but any function
     returning an iterable should work.
@@ -474,19 +469,7 @@ def album_field_getters() -> TFuncMap[Album]:
 # Event dispatch.
 
 
-def event_handlers() -> dict[str, list[Listener]]:
+def send(event: EventType, **arguments: Any) -> list[Any]:
-    """Find all event handlers from plugins as a dictionary mapping
-    event names to sequences of callables.
-    """
-    all_handlers: dict[str, list[Listener]] = defaultdict(list)
-    for plugin in find_plugins():
-        if plugin.listeners:
-            for event, handlers in plugin.listeners.items():
-                all_handlers[event] += handlers
-    return all_handlers
-
-
-def send(event: str, **arguments: Any) -> list[Any]:
     """Send an event to all assigned event listeners.
 
     `event` is the name of  the event to send, all other named arguments
@@ -495,12 +478,11 @@ def send(event: str, **arguments: Any) -> list[Any]:
     Return a list of non-None values returned from the handlers.
     """
     log.debug("Sending event: {0}", event)
-    results: list[Any] = []
+    return [
-    for handler in event_handlers()[event]:
+        r
-        result = handler(**arguments)
+        for handler in BeetsPlugin.listeners[event]
-        if result is not None:
+        if (r := handler(**arguments)) is not None
-            results.append(result)
+    ]
-    return results
 
 
 def feat_tokens(for_artist: bool = True) -> str:

beets/test/helper.py

@@ -498,8 +498,8 @@ class PluginMixin(ConfigMixin):
     def unload_plugins(self) -> None:
         """Unload all plugins and remove them from the configuration."""
         # FIXME this should eventually be handled by a plugin manager
-        for plugin_class in beets.plugins._instances:
+        beets.plugins.BeetsPlugin.listeners.clear()
-            plugin_class.listeners = None
+        beets.plugins.BeetsPlugin._raw_listeners.clear()
         self.config["plugins"] = []
         beets.plugins._classes = set()
         beets.plugins._instances = {}

test/test_plugins.py

@@ -243,15 +243,7 @@ class ListenersTest(PluginLoaderTestCase):
         d.register_listener("cli_exit", d2.dummy)
         assert DummyPlugin._raw_listeners["cli_exit"] == [d.dummy, d2.dummy]
 
-    @patch("beets.plugins.find_plugins")
+    def test_events_called(self):
-    @patch("inspect.getfullargspec")
-    def test_events_called(self, mock_gfa, mock_find_plugins):
-        mock_gfa.return_value = Mock(
-            args=(),
-            varargs="args",
-            varkw="kwargs",
-        )
-
         class DummyPlugin(plugins.BeetsPlugin):
             def __init__(self):
                 super().__init__()
@@ -261,7 +253,6 @@ class ListenersTest(PluginLoaderTestCase):
                 self.register_listener("event_bar", self.bar)
 
         d = DummyPlugin()
-        mock_find_plugins.return_value = (d,)
 
         plugins.send("event")
         d.foo.assert_has_calls([])
@@ -271,8 +262,7 @@ class ListenersTest(PluginLoaderTestCase):
         d.foo.assert_called_once_with(var="tagada")
         d.bar.assert_has_calls([])
 
-    @patch("beets.plugins.find_plugins")
+    def test_listener_params(self):
-    def test_listener_params(self, mock_find_plugins):
         class DummyPlugin(plugins.BeetsPlugin):
             def __init__(self):
                 super().__init__()
@@ -316,8 +306,7 @@ class ListenersTest(PluginLoaderTestCase):
             def dummy9(self, **kwargs):
                 assert kwargs == {"foo": 5}
 
-        d = DummyPlugin()
+        DummyPlugin()
-        mock_find_plugins.return_value = (d,)
 
         plugins.send("event1", foo=5)
         plugins.send("event2", foo=5)