[GitHub] [superset] villebro commented on a change in pull request #17470: fix(presto): expand data with null item

[GitBox <gi...@apache.org>]

villebro commented on a change in pull request #17470:
URL: https://github.com/apache/superset/pull/17470#discussion_r751957706



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File path: superset/db_engine_specs/presto.py
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@@ -872,7 +872,7 @@ def expand_data(  # pylint: disable=too-many-locals
                     values = row.get(name) or []
                     if isinstance(values, str):
                         row[name] = values = cast(List[Any], destringify(values))
-                    for value, col in zip(values, expanded):
+                    for value, col in zip(values or [], expanded):

Review comment:
       As the destringified values may be `None`, we should probably also update line 874 to reflect this by updating the cast to more accurately reflect the expected return value:
   ```python
   row[name] = values = cast(Optional[List[Any]], destringify(values))
   ```
   With this change mypy would see that `values` may be `None`. Alternatively we may want to move the `or []` up one line, but in this case the return value will change (not sure which is better).




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