fix(api): Fix variable truncation for list[File] value in output mapping (#26133)

api/services/variable_truncator.py

@@ -262,6 +262,14 @@ class VariableTruncator:
         target_length = self._array_element_limit
 
         for i, item in enumerate(value):
+            # Dirty fix:
+            # The output of `Start` node may contain list of `File` elements,
+            # causing `AssertionError` while invoking `_truncate_json_primitives`.
+            #
+            # This check ensures that `list[File]` are handled separately
+            if isinstance(item, File):
+                truncated_value.append(item)
+                continue
             if i >= target_length:
                 return _PartResult(truncated_value, used_size, True)
             if i > 0:

api/tests/unit_tests/services/test_variable_truncator.py

@@ -588,3 +588,11 @@ class TestIntegrationScenarios:
             if isinstance(result.result, ObjectSegment):
                 result_size = truncator.calculate_json_size(result.result.value)
                 assert result_size <= original_size
+
+    def test_file_and_array_file_variable_mapping(self, file):
+        truncator = VariableTruncator(string_length_limit=30, array_element_limit=3, max_size_bytes=300)
+
+        mapping = {"array_file": [file]}
+        truncated_mapping, truncated = truncator.truncate_variable_mapping(mapping)
+        assert truncated is False
+        assert truncated_mapping == mapping