fix(csv): Ensure df_to_escaped_csv handles NULL (apache#20151)

Co-authored-by: John Bodley <john.bodley@airbnb.com>

superset/utils/csv.py

@@ -19,6 +19,7 @@
 from typing import Any, Dict, Optional
 from urllib.error import URLError
 
+import numpy as np
 import pandas as pd
 import simplejson
 
@@ -64,8 +65,12 @@ def df_to_escaped_csv(df: pd.DataFrame, **kwargs: Any) -> Any:
     # Escape csv headers
     df = df.rename(columns=escape_values)
 
-    # Escape csv rows
-    df = df.applymap(escape_values)
+    # Escape csv values
+    for name, column in df.items():
+        if column.dtype == np.dtype(object):
+            for idx, value in enumerate(column.values):
+                if isinstance(value, str):
+                    df.at[idx, name] = escape_value(value)
 
     return df.to_csv(**kwargs)
 

tests/integration_tests/utils/csv_tests.py

@@ -17,6 +17,7 @@
 import io
 
 import pandas as pd
+import pyarrow as pa
 import pytest
 
 from superset.utils import csv
@@ -77,3 +78,6 @@ def test_df_to_escaped_csv():
         ["a", "'=b"],  # pandas seems to be removing the leading ""
         ["' =a", "b"],
     ]
+
+    df = pa.array([1, None]).to_pandas(integer_object_nulls=True).to_frame()
+    assert csv.df_to_escaped_csv(df, encoding="utf8", index=False) == '0\n1\n""\n'