Preserve spreadsheet error codes in cell values

src/types/cell.rs

@@ -114,6 +114,11 @@ where
                     .map(|s| CellValue::String(s.to_owned()))
                     .unwrap_or(CellValue::Empty),
             )
+        } else if value.is_error() {
+            value
+                .get_error()
+                .map(|error| CellValue::String(error.to_string()))
+                .unwrap_or(CellValue::Empty)
         } else if value.is_bool() {
             value
                 .get_bool()

tests/test_error_cells.py

@@ -0,0 +1,19 @@
+from pathlib import Path
+
+import pytest
+from python_calamine import CalamineWorkbook
+
+DATA = Path(__file__).parent / "data"
+COMMON_ERRORS = ["#NULL!", "#DIV/0!", "#VALUE!", "#REF!", "#NAME?", "#NUM!", "#N/A"]
+
+
+@pytest.mark.parametrize(
+    ("filename", "errors"),
+    [("error-cells.xlsx", COMMON_ERRORS), ("error-cells.xls", [*COMMON_ERRORS, "#DATA!"])],
+)
+def test_error_cells_keep_codes_in_both_sheet_apis(filename, errors):
+    with CalamineWorkbook.from_path(DATA / filename) as workbook:
+        sheet = workbook.get_sheet_by_name("Errors")
+        expected = [errors + ["", "#N/A"]]
+        assert list(sheet.iter_rows()) == expected
+        assert sheet.to_python() == expected