fix broken repr in file monitor (#2795)

* fix broken repr in file monitor

* no need for callback

* docstrings and typing

Author: willmcgugan

src/textual/_callback.py

@@ -37,7 +37,7 @@ async def _invoke(callback: Callable, *params: object) -> Any:
     return result
 
 
-async def invoke(callback: Callable, *params: object) -> Any:
+async def invoke(callback: Callable[[], Any], *params: object) -> Any:
     """Invoke a callback with an arbitrary number of parameters.
 
     Args:

src/textual/file_monitor.py

@@ -15,11 +15,20 @@ class FileMonitor:
 
     _paths: set[Path]
 
-    def __init__(self, paths: Sequence[Path], callback: Callable) -> None:
+    def __init__(self, paths: Sequence[Path], callback: Callable[[], None]) -> None:
+        """Monitor the given file paths for changes.
+
+        Args:
+            paths: Paths to monitor.
+            callback: Callback to invoke if any of the paths change.
+        """
         self._paths = set(paths)
         self.callback = callback
         self._modified = self._get_last_modified_time()
 
+    def __rich_repr__(self) -> rich.repr.Result:
+        yield self._paths
+
     def _get_last_modified_time(self) -> float:
         """Get the most recent modified time out of all files being watched."""
         return max(os.stat(path).st_mtime for path in self._paths)

tests/test_file_monitor.py

@@ -0,0 +1,8 @@
+from pathlib import Path
+
+from textual.file_monitor import FileMonitor
+
+
+def test_repr() -> None:
+    file_monitor = FileMonitor([Path(".")], lambda: None)
+    assert "FileMonitor" in repr(file_monitor)