Added typehints for _instance, _classes and for class attributes.

beets/plugins.py

@@ -24,9 +24,11 @@ from collections import defaultdict
 from functools import wraps
 from typing import (
     TYPE_CHECKING,
+    Any,
     Callable,
     Generic,
     Sequence,
+    Type,
     TypedDict,
     TypeVar,
 )
@@ -39,9 +41,11 @@ from beets import logging
 if TYPE_CHECKING:
     from collections.abc import Iterable
 
+    from confuse import ConfigView
+
     from beets.autotag import AlbumInfo, Distance, TrackInfo
     from beets.dbcore import Query
-    from beets.library import Item, Library
+    from beets.library import Album, Item, Library
     from beets.ui import Subcommand
 
 
@@ -79,6 +83,10 @@ class PluginLogFilter(logging.Filter):
         return True
 
 
+# Typing for listeners
+CallableWithAnyKwargs = Callable[[None, Any], None]
+
+
 # Managing the plugins themselves.
 
 
@@ -88,16 +96,24 @@ class BeetsPlugin:
     the abstract methods defined here.
     """
 
+    name: str
+    config: ConfigView
+
     def __init__(self, name=None):
         """Perform one-time plugin setup."""
+
         self.name = name or self.__module__.split(".")[-1]
         self.config = beets.config[self.name]
+
+        # Set class attributes if they are not already set
+        # for the type of plugin.
         if not self.template_funcs:
             self.template_funcs = {}
         if not self.template_fields:
             self.template_fields = {}
         if not self.album_template_fields:
             self.album_template_fields = {}
+
         self.early_import_stages = []
         self.import_stages = []
 
@@ -243,13 +259,14 @@ class BeetsPlugin:
         mediafile.MediaFile.add_field(name, descriptor)
         library.Item._media_fields.add(name)
 
-    _raw_listeners = None
+    _raw_listeners: dict[str, list[Callable[[None, Any], None]]] | None = None
-    listeners: None | dict[str, list[Callable]] = None
+    listeners: dict[str, list[Callable[[None, Any], None]]] | None = None
 
-    def register_listener(self, event: str, func: Callable):
+    def register_listener(self, event: str, func: CallableWithAnyKwargs):
         """Add a function as a listener for the specified event."""
         wrapped_func = self._set_log_level_and_params(logging.WARNING, func)
 
+        cls = self.__class__
         cls = self.__class__
         if cls.listeners is None or cls._raw_listeners is None:
             cls._raw_listeners = defaultdict(list)
@@ -258,9 +275,9 @@ class BeetsPlugin:
             cls._raw_listeners[event].append(func)
             cls.listeners[event].append(wrapped_func)
 
-    template_funcs = None
+    template_funcs: dict[str, Callable[[str, Any], str]] | None = None
-    template_fields = None
+    template_fields: dict[str, Callable[[Item], str]] | None = None
-    album_template_fields = None
+    album_template_fields: dict[str, Callable[[Album], str]] | None = None
 
     @classmethod
     def template_func(cls, name: str):
@@ -294,7 +311,7 @@ class BeetsPlugin:
         return helper
 
 
-_classes = set()
+_classes: set[type[BeetsPlugin]] = set()
 
 
 def load_plugins(names: Sequence[str] = ()):
@@ -332,7 +349,7 @@ def load_plugins(names: Sequence[str] = ()):
             )
 
 
-_instances = {}
+_instances: dict[Type[BeetsPlugin], BeetsPlugin] = {}
 
 
 def find_plugins() -> list[BeetsPlugin]:
@@ -544,7 +561,7 @@ def event_handlers():
     return all_handlers
 
 
-def send(event, **arguments):
+def send(event: str, **arguments: Any):
     """Send an event to all assigned event listeners.
 
     `event` is the name of  the event to send, all other named arguments

docs/dev/plugins.rst

@@ -367,7 +367,7 @@ Here's an example::
             super().__init__()
             self.template_funcs['initial'] = _tmpl_initial
 
-    def _tmpl_initial(text):
+    def _tmpl_initial(text:str) -> str:
         if text:
             return text[0].upper()
         else:
@@ -387,7 +387,7 @@ Here's an example that adds a ``$disc_and_track`` field::
             super().__init__()
             self.template_fields['disc_and_track'] = _tmpl_disc_and_track
 
-    def _tmpl_disc_and_track(item):
+    def _tmpl_disc_and_track(item: Item) -> str:
         """Expand to the disc number and track number if this is a
         multi-disc release. Otherwise, just expands to the track
         number.