Ovelapping intervals: setting default values when creating a parameter

src/View/WeatherParameters/Table.py

@@ -248,13 +248,18 @@ class WeatherParametersTableModel(PamhyrTableModel):
                 )
             elif self._headers[column] == "reach":
                 new_reach = self._river.edge(value)
-                if self._overlaps_existing_interval(
-                        row, reach=new_reach):
+                overlaps = self._overlaps_existing_interval(
+                    row, reach=new_reach
+                )
+                current = self._lst[row]
+                clear_interval = overlaps and current.reach is None
+                if overlaps and not clear_interval:
                     self._show_overlap_warning()
                     return False
                 self._undo.push(
                     SetEdgeCommand(
-                        self._data, global_row, new_reach
+                        self._data, global_row, new_reach,
+                        clear_interval=clear_interval
                     )
                 )
         except Exception as e:

src/View/WeatherParameters/UndoCommand.py

@@ -120,19 +120,27 @@ class SetEndCommand(QUndoCommand):
 
 
 class SetEdgeCommand(QUndoCommand):
-    def __init__(self, wps, index, edge):
+    def __init__(self, wps, index, edge, clear_interval=False):
         QUndoCommand.__init__(self)
 
         self._wps = wps
         self._index = index
         self._old = self._wps.get(self._index).reach
+        self._old_begin = self._wps.get(self._index).begin_section
+        self._old_end = self._wps.get(self._index).end_section
         self._new = edge
+        self._clear_interval = clear_interval
 
     def undo(self):
         self._wps.get(self._index).reach = self._old
+        self._wps.get(self._index).begin_section = self._old_begin
+        self._wps.get(self._index).end_section = self._old_end
 
     def redo(self):
         self._wps.get(self._index).reach = self._new
+        if self._clear_interval:
+            self._wps.get(self._index).begin_section = None
+            self._wps.get(self._index).end_section = None
 
 
 class AddCommand(QUndoCommand):