feat: Allow to replace selection content in with one event emmited (#387)

Author: Czaki

src/psygnal/containers/_selection.py

@@ -5,7 +5,7 @@
 
 from psygnal._signal import Signal
 
-from ._evented_set import BailType, EventedOrderedSet, SetEvents
+from ._evented_set import BailType, EventedOrderedSet, SetEvents, _reduce_events
 
 if TYPE_CHECKING:
     from collections.abc import Iterable
@@ -131,8 +131,19 @@ def toggle(self, obj: _T) -> None:
 
     def select_only(self, obj: _T) -> None:
         """Unselect everything but `obj`. Add to selection if not currently selected."""
-        self.intersection_update({obj})
-        self.add(obj)
+        with self.events.items_changed.paused(_reduce_events):
+            self.intersection_update({obj})
+            self.add(obj)
+
+    def replace_selection(self, new_selection: Iterable[_T]) -> None:
+        """Replace the current selection with `new_selection`.
+
+        This is equivalent to calling `intersection_update` followed by `update`,
+        but is more efficient because it only emits a single `items_changed` event.
+        """
+        with self.events.items_changed.paused(_reduce_events):
+            self.intersection_update(new_selection)
+            self.update(new_selection)
 
     def _update_active(self) -> None:
         """On a selection event, update the active item based on selection.

tests/containers/test_selection.py

@@ -59,10 +59,13 @@ def test_active_setter():
 
 
 def test_select_only():
+    mock = Mock()
     selection = Selection([1, 2])
     selection.active = 1
     assert selection.active == 1
+    selection.events.items_changed.connect(mock)
     selection.select_only(2)
+    mock.assert_called_once_with((2,), (1,))
     assert selection.active == 2
 
 
@@ -94,3 +97,13 @@ def test_emit_change():
 
 def test_hash():
     assert hash(Selection())
+
+
+def test_replace_selection():
+    mock = Mock()
+    selection = Selection([1, 2, 3])
+
+    selection.events.items_changed.connect(mock)
+    selection.replace_selection([3, 4, 5])
+    mock.assert_called_once_with((4, 5), (1, 2))
+    assert set(selection) == {3, 4, 5}