fix(scan_control): restore scan parameters always regenerate the arg box, preventing infinite loop

bec_widgets/widgets/control/scan_control/scan_group_box.py

@@ -281,6 +281,17 @@ class ScanGroupBox(QGroupBox):
         selected_devices_str = " ".join(self.selected_devices.values())
         self.device_selected.emit(selected_devices_str.strip())
 
+    def remove_all_widget_bundles(self):
+        """Remove every widget bundle from the scan control layout."""
+        for widget in list(self.widgets):
+            if isinstance(widget, DeviceLineEdit):
+                self.selected_devices.pop(widget, None)
+            widget.close()
+            widget.deleteLater()
+            self.layout.removeWidget(widget)
+        self.widgets.clear()
+        self.device_selected.emit("")
+
     @Property(bool)
     def hide_add_remove_buttons(self):
         return self._hide_add_remove_buttons
@@ -349,10 +360,21 @@ class ScanGroupBox(QGroupBox):
             self._set_kwarg_parameters(parameters)
 
     def _set_arg_parameters(self, parameters: list):
-        while len(parameters) != len(self.widgets):
-            self.add_widget_bundle()
-        for i, parameter in enumerate(parameters):
-            WidgetIO.set_value(self.widgets[i], parameter)
+        self.remove_all_widget_bundles()
+        if not parameters:
+            return
+
+        inputs_per_bundle = len(self.inputs)
+        if inputs_per_bundle == 0:
+            return
+
+        bundles_needed = -(-len(parameters) // inputs_per_bundle)
+
+        for row in range(1, bundles_needed + 1):
+            self.add_input_widgets(self.inputs, row)
+
+        for i, value in enumerate(parameters):
+            WidgetIO.set_value(self.widgets[i], value)
 
     def _set_kwarg_parameters(self, parameters: dict):
         for widget in self.widgets:

tests/unit_tests/test_scan_control.py

@@ -558,3 +558,31 @@ def test_scan_metadata_is_connected(scan_control):
         "test key 1": "test value 1",
         "test key 2": "test value 2",
     }
+
+
+def test_restore_parameters_with_fewer_arg_bundles(scan_control, qtbot):
+    """
+    Ensure that when more argument bundles are present than exist in the
+    stored history, restoring parameters regenerates the arg box to the
+    correct (smaller) size and sets the values properly.
+    This is a check for the previous infinite loop bug.
+    """
+    # Select the scan type that has history with only one arg bundle
+    scan_control.comboBox_scan_selection.setCurrentText("line_scan")
+
+    # Manually add bundles so we end up with three rows
+    while scan_control.arg_box.count_arg_rows() < 3:
+        scan_control.arg_box.add_widget_bundle()
+    assert scan_control.arg_box.count_arg_rows() == 3
+
+    # Trigger restore of parameters from history
+    scan_control.toggle.checked = True
+    qtbot.wait(200)
+
+    # After restore, arg_box should have only one bundle (the history size)
+    assert scan_control.arg_box.count_arg_rows() == 1
+
+    # Verify that the restored parameter values match the history
+    args, kwargs = scan_control.get_scan_parameters(bec_object=False)
+    assert args == ["samx", 0.0, 2.0]
+    assert kwargs["steps"] == 10