Add watcher mods

hmr/_watcher.py

@@ -0,0 +1,92 @@
+from __future__ import annotations
+
+__all__ = ["Watchers"]
+
+import atexit
+import sys
+import traceback
+from datetime import datetime
+from typing import Dict, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from ._reload import BaseReloader
+
+from watchdog.events import FileSystemEventHandler
+from watchdog.observers import Observer
+from watchdog.observers.api import ObservedWatch
+
+
+class EventsHandler(FileSystemEventHandler):
+    reload_list = []
+    _last_error = None
+
+    def on_any_event(self, event):
+        # print(event.src_path, event.event_type, event.is_directory)
+        # print("Reload list", self.reload_list)
+        for reloader in self.reload_list:
+            try:
+                reloader.__reload__()
+            except Exception:
+                _current = datetime.now()
+                error_stack = traceback.extract_stack()
+                # only fire the same error once
+                if self._last_error is None or self._last_error != error_stack:
+                    self._last_error = error_stack
+                    traceback.print_exc(file=sys.stderr)
+        return
+
+
+class WatcherStorage:
+    def __init__(self):
+        self._observer = None
+        self.watchers: Dict[str, (ObservedWatch, EventsHandler)] = {}
+
+        atexit.register(self.__del__)
+
+    @property
+    def observer(self) -> Observer:
+        if self._observer is None:
+            self._observer = Observer()
+            self._observer.daemon = True
+            self._observer.start()
+        return self._observer
+
+    def add_reload(self, reloader: BaseReloader):
+        root_path = reloader.__proxy_module__.root_path
+        watcher = self.watchers.get(root_path)
+        if watcher is None:
+            event_handler = EventsHandler()
+            event_handler.reload_list.append(reloader)
+            watch = self.observer.schedule(event_handler, root_path, recursive=True)
+            self.watchers[root_path] = (watch, event_handler)
+        else:
+            watch, event_handler = watcher
+            event_handler.reload_list.append(reloader)
+
+    def delete_reload(self, reloader: BaseReloader):
+        root_path = reloader.__proxy_module__.root_path
+        watcher = self.watchers.get(root_path)
+        if watcher is not None:
+            watch, event_handler = watcher
+            # This may be emitted multiple times
+            # Must wrap in a try-except block
+            try:
+                event_handler.reload_list.remove(reloader)
+                if not event_handler.reload_list:
+                    self.observer.unschedule(watch)
+                    del self.watchers[root_path]
+            except (ValueError, KeyError):
+                pass
+
+    def __del__(self):
+        if self._observer is not None:
+            self._observer.unschedule_all()
+            self._observer.stop()
+            self._observer.join()
+
+
+Watchers = WatcherStorage()
+
+
+# def get_watchers():
+#     return Watchers