BUG: Tackle GH47203; Ensure body is non-empty when accessing row_body_cells (#47204)

Author: tomaarsen

doc/source/whatsnew/v1.5.0.rst

@@ -900,6 +900,7 @@ Styler
 - Bug when attempting to apply styling functions to an empty DataFrame subset (:issue:`45313`)
 - Bug in :class:`CSSToExcelConverter` leading to ``TypeError`` when border color provided without border style for ``xlsxwriter`` engine (:issue:`42276`)
 - Bug in :meth:`Styler.set_sticky` leading to white text on white background in dark mode (:issue:`46984`)
+- Bug in :meth:`Styler.to_latex` causing ``UnboundLocalError`` when ``clines="all;data"`` and the ``DataFrame`` has no rows. (:issue:`47203`)
 
 Metadata
 ^^^^^^^^

pandas/io/formats/style_render.py

@@ -908,7 +908,7 @@ def concatenated_visible_rows(obj, n, row_indices):
                 f"of 'all;data', 'all;index', 'skip-last;data', 'skip-last;index'."
             )
         elif clines is not None:
-            data_len = len(row_body_cells) if "data" in clines else 0
+            data_len = len(row_body_cells) if "data" in clines and d["body"] else 0
 
             d["clines"] = defaultdict(list)
             visible_row_indexes: list[int] = [

pandas/tests/io/formats/style/test_to_latex.py

@@ -1032,3 +1032,36 @@ def test_concat_recursion():
     """
     )
     assert result == expected
+
+
+@pytest.mark.parametrize(
+    "df, expected",
+    [
+        (
+            DataFrame(),
+            dedent(
+                """\
+            \\begin{tabular}{l}
+            \\end{tabular}
+            """
+            ),
+        ),
+        (
+            DataFrame(columns=["a", "b", "c"]),
+            dedent(
+                """\
+            \\begin{tabular}{llll}
+             & a & b & c \\\\
+            \\end{tabular}
+            """
+            ),
+        ),
+    ],
+)
+@pytest.mark.parametrize(
+    "clines", [None, "all;data", "all;index", "skip-last;data", "skip-last;index"]
+)
+def test_empty_clines(df: DataFrame, expected: str, clines: str):
+    # GH 47203
+    result = df.style.to_latex(clines=clines)
+    assert result == expected