fix: treat #REF! cells as nulls (#244)

Signed-off-by: Luka Peschke <[email protected]>

python/tests/test_fastexcel.py

@@ -477,6 +477,20 @@ def test_sheet_with_na():
     pl_assert_frame_equal(sheet.to_polars(), pl.DataFrame(expected))
 
 
+def test_sheet_with_ref():
+    """Test reading a sheet with #REF! cells. For now, we consider them as null"""
+    excel_reader = fastexcel.read_excel(path_for_fixture("sheet-with-na.xlsx"))
+    sheet = excel_reader.load_sheet("Broken refs")
+
+    assert sheet.name == "Broken refs"
+    assert sheet.height == sheet.total_height == 2
+    assert sheet.width == 1
+
+    expected = {"numbers": [1.0, None]}
+    pd_assert_frame_equal(sheet.to_pandas(), pd.DataFrame(expected))
+    pl_assert_frame_equal(sheet.to_polars(), pl.DataFrame(expected))
+
+
 @pytest.mark.parametrize("excel_file", ["sheet-null-strings.xlsx", "sheet-null-strings-empty.xlsx"])
 def test_null_strings(excel_file: str):
     excel_reader = fastexcel.read_excel(path_for_fixture(excel_file))

src/types/dtype.rs

@@ -159,8 +159,10 @@ fn get_cell_dtype<DT: CellType + Debug + DataType>(
         Ok(DType::Null)
     } else if cell.is_error() {
         match cell.get_error() {
-            // considering cells with #N/A! as null
-            Some(CellErrorType::NA | CellErrorType::Value | CellErrorType::Null) => Ok(DType::Null),
+            // considering cells with #N/A! or #REF! as null
+            Some(
+                CellErrorType::NA | CellErrorType::Value | CellErrorType::Null | CellErrorType::Ref,
+            ) => Ok(DType::Null),
             Some(err) => Err(FastExcelErrorKind::CalamineCellError(err.to_owned()).into()),
             None => Err(FastExcelErrorKind::Internal(format!(
                 "cell is an error but get_error returned None: {cell:?}"