Fix handling of place_correct_choice_position (#1511)

Fix: Improved handling of `place_correct_choice_position` for flexible input sizes

- Added logic to ensure `place_correct_choice_position` works correctly for varying numbers of choices.
- Implemented two approaches:
  1. Clamping the position to ensure it remains within valid bounds.
  2. Supporting negative indexing to allow placing the correct choice at the end with `-1`.
- Ensured the implementation avoids crashes and provides robust handling for edge cases.

Co-authored-by: Elron Bandel <[email protected]>

src/unitxt/templates.py

@@ -694,6 +694,21 @@ def preprocess_input_and_reference_fields(
             )
             random_generator.shuffle(choices)
         if self.place_correct_choice_position is not None:
+            fix_pos = self.place_correct_choice_position
+
+            # Option 1: Clamping the position to the valid range
+            # Force the position to be within the valid range [0, len(choices)-1].
+            # If fix_pos is less than 0, it becomes 0.
+            # If fix_pos is greater than len(choices)-1, it becomes len(choices)-1.
+            fix_pos = max(0, min(fix_pos, len(choices) - 1))
+
+            # Option 2: Supporting negative indexes similar to Python lists
+            # If fix_pos is negative, convert it to a valid positive index by adding len(choices).
+            # For example, -1 becomes the last index, -2 becomes the one before last, etc.
+            if fix_pos < 0:
+                fix_pos += len(choices)
+            self.place_correct_choice_position = fix_pos
+            # Remove the original label choice from the list
             if not 0 <= self.place_correct_choice_position < len(choices):
                 raise ValueError(
                     f"fix_correct_choice_position={self.place_correct_choice_position} out of range (0..{len(choices) - 1})."