Fix: blank cells in .xlsx/.xls render as NaN in markdown output

Author: WolffM

.github/copilot-instructions.md

@@ -84,7 +84,7 @@ def convert(
         md_content = ""
         for s in sheets:
             md_content += f"## {s}\n"
-            html_content = sheets[s].to_html(index=False)
+            html_content = sheets[s].to_html(index=False, na_rep="")
             md_content += (
                 self._html_converter.convert_string(
                     html_content, **kwargs
@@ -146,7 +146,7 @@ def convert(
         md_content = ""
         for s in sheets:
             md_content += f"## {s}\n"
-            html_content = sheets[s].to_html(index=False)
+            html_content = sheets[s].to_html(index=False, na_rep="")
             md_content += (
                 self._html_converter.convert_string(
                     html_content, **kwargs

.github/workflows/ci.yml

@@ -382,6 +382,17 @@ def test_exceptions() -> None:
     assert type(exc_info.value.attempts[0].converter).__name__ == "PptxConverter"
 
 
+def test_xlsx_blank_cells() -> None:
+    # Blank cells in .xlsx should render as empty strings, not "NaN"
+    markitdown = MarkItDown()
+    result = markitdown.convert(
+        os.path.join(TEST_FILES_DIR, "test_xlsx_blank_cells.xlsx")
+    )
+    assert "NaN" not in result.markdown
+    assert "Alice" in result.markdown
+    assert "Bob" in result.markdown
+
+
 @pytest.mark.skipif(
     skip_exiftool,
     reason="do not run if exiftool is not installed",