REGR: Styler buf and encoding in to_latex and to_html (#47059)

Author: attack68

doc/source/whatsnew/v1.4.3.rst

@@ -16,7 +16,7 @@ Fixed regressions
 ~~~~~~~~~~~~~~~~~
 - Fixed regression in :meth:`DataFrame.nsmallest` led to wrong results when ``np.nan`` in the sorting column (:issue:`46589`)
 - Fixed regression in :func:`read_fwf` raising ``ValueError`` when ``widths`` was specified with ``usecols`` (:issue:`46580`)
--
+- Fixed regression is :meth:`.Styler.to_latex` and :meth:`.Styler.to_html` where ``buf`` failed in combination with ``encoding`` (:issue:`47053`)
 
 .. ---------------------------------------------------------------------------
 

pandas/io/formats/style.py

@@ -1153,10 +1153,12 @@ def to_latex(
             clines=clines,
         )
 
-        encoding = encoding or get_option("styler.render.encoding")
-        return save_to_buffer(
-            latex, buf=buf, encoding=None if buf is None else encoding
+        encoding = (
+            (encoding or get_option("styler.render.encoding"))
+            if isinstance(buf, str)  # i.e. a filepath
+            else encoding
         )
+        return save_to_buffer(latex, buf=buf, encoding=encoding)
 
     @Substitution(buf=buf, encoding=encoding)
     def to_html(
@@ -1273,15 +1275,14 @@ def to_html(
         if caption is not None:
             obj.set_caption(caption)
 
-        encoding = encoding or get_option("styler.render.encoding")
         # Build HTML string..
         html = obj._render_html(
             sparse_index=sparse_index,
             sparse_columns=sparse_columns,
             max_rows=max_rows,
             max_cols=max_columns,
             exclude_styles=exclude_styles,
-            encoding=encoding,
+            encoding=encoding or get_option("styler.render.encoding"),
             doctype_html=doctype_html,
             **kwargs,
         )

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

@@ -1557,3 +1557,10 @@ def test_no_empty_apply(mi_styler):
     # 45313
     mi_styler.apply(lambda s: ["a:v;"] * 2, subset=[False, False])
     mi_styler._compute()
+
+
+@pytest.mark.parametrize("format", ["html", "latex", "string"])
+def test_output_buffer(mi_styler, format):
+    # gh 47053
+    with open(f"delete_me.{format}", "w") as f:
+        getattr(mi_styler, f"to_{format}")(f)