warn and expand tests

pandas-dev · attack68 · Nov 12, 2021 · Nov 12, 2021 · Nov 12, 2021 · Nov 12, 2021
commit 310bdc2fa099599bbb57e4291847a53a02cbd06a
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
@@ -2855,6 +2855,15 @@ def to_html(
         --------
         to_string : Convert DataFrame to a string.
         """
+        msg = (
+            "In future versions `DataFrame.to_html` is expected to utilise the base "
+            "implementation of `Styler.to_html` for formatting and rendering. "
+            "The arguments signature may therefore change. It is recommended instead "
+            "to use `DataFrame.style.to_html` which also contains additional "
+            "functionality."
+        )
+        warnings.warn(msg, FutureWarning, stacklevel=find_stack_level())
+
         if justify is not None and justify not in fmt._VALID_JUSTIFY_PARAMETERS:
             raise ValueError("Invalid value for justify parameter")
 

diff --git a/pandas/tests/io/formats/test_format.py b/pandas/tests/io/formats/test_format.py
@@ -3299,6 +3299,7 @@ def test_repr_html_ipython_config(ip):
 
 
 @pytest.mark.filterwarnings("ignore:In future versions `DataFrame.to_latex`")
+@pytest.mark.filterwarnings("ignore:In future versions `DataFrame.to_html`")
 @pytest.mark.parametrize("method", ["to_string", "to_html", "to_latex"])
 @pytest.mark.parametrize(
     "encoding, data",
@@ -3320,7 +3321,7 @@ def test_filepath_or_buffer_arg(
         ):
             getattr(df, method)(buf=filepath_or_buffer, encoding=encoding)
     elif encoding == "foo":
-        expected_warning = FutureWarning if method == "to_latex" else None
+        expected_warning = FutureWarning if method in ["to_latex", "to_html"] else None
         with tm.assert_produces_warning(expected_warning):
             with pytest.raises(LookupError, match="unknown encoding"):
                 getattr(df, method)(buf=filepath_or_buffer, encoding=encoding)