Cursor left and right standardisation when theres an active selection

Author: darrenburns

src/textual/widgets/_text_area.py

@@ -1838,8 +1838,12 @@ def action_cursor_left(self, select: bool = False) -> None:
         Args:
             select: If True, select the text while moving.
         """
-        target = self.get_cursor_left_location()
-        self.move_cursor(target, select=select)
+        if self.selection.is_empty:
+            target = self.get_cursor_left_location()
+            self.move_cursor(target, select=select)
+        else:
+            start, end = self.selection
+            self.move_cursor(min(start, end), select=select)
 
     def get_cursor_left_location(self) -> Location:
         """Get the location the cursor will move to if it moves left.
@@ -1857,8 +1861,12 @@ def action_cursor_right(self, select: bool = False) -> None:
         Args:
             select: If True, select the text while moving.
         """
-        target = self.get_cursor_right_location()
-        self.move_cursor(target, select=select)
+        if self.selection.is_empty:
+            target = self.get_cursor_right_location()
+            self.move_cursor(target, select=select)
+        else:
+            start, end = self.selection
+            self.move_cursor(max(start, end), select=select)
 
     def get_cursor_right_location(self) -> Location:
         """Get the location the cursor will move to if it moves right.