TST: Improved test coverage for Styler.bar error conditions (#56341)

* Improved test coverage for Styler.bar error conditions

* Fixed the code style issue causing test failure

* Fixed a Styler.bar bug of missing value

* Adopted another tricky way to fix the bug

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Added a test for Styler.bar with pyarrow

* Updated with code style

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

pandas/io/formats/style.py

@@ -4082,8 +4082,9 @@ def css_calc(x, left: float, right: float, align: str, color: str | list | tuple
             return ret
 
     values = data.to_numpy()
-    left = np.nanmin(values) if vmin is None else vmin
-    right = np.nanmax(values) if vmax is None else vmax
+    # A tricky way to address the issue where np.nanmin/np.nanmax fail to handle pd.NA.
+    left = np.nanmin(data.min(skipna=True)) if vmin is None else vmin
+    right = np.nanmax(data.max(skipna=True)) if vmax is None else vmax
     z: float = 0  # adjustment to translate data
 
     if align == "mid":

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

@@ -1,7 +1,13 @@
+import io
+
 import numpy as np
 import pytest
 
-from pandas import DataFrame
+from pandas import (
+    NA,
+    DataFrame,
+    read_csv,
+)
 
 pytest.importorskip("jinja2")
 
@@ -305,3 +311,48 @@ def test_bar_value_error_raises():
     msg = r"`height` must be a value in \[0, 100\]"
     with pytest.raises(ValueError, match=msg):
         df.style.bar(height=200).to_html()
+
+
+def test_bar_color_and_cmap_error_raises():
+    df = DataFrame({"A": [1, 2, 3, 4]})
+    msg = "`color` and `cmap` cannot both be given"
+    # Test that providing both color and cmap raises a ValueError
+    with pytest.raises(ValueError, match=msg):
+        df.style.bar(color="#d65f5f", cmap="viridis").to_html()
+
+
+def test_bar_invalid_color_type_error_raises():
+    df = DataFrame({"A": [1, 2, 3, 4]})
+    msg = (
+        r"`color` must be string or list or tuple of 2 strings,"
+        r"\(eg: color=\['#d65f5f', '#5fba7d'\]\)"
+    )
+    # Test that providing an invalid color type raises a ValueError
+    with pytest.raises(ValueError, match=msg):
+        df.style.bar(color=123).to_html()
+
+    # Test that providing a color list with more than two elements raises a ValueError
+    with pytest.raises(ValueError, match=msg):
+        df.style.bar(color=["#d65f5f", "#5fba7d", "#abcdef"]).to_html()
+
+
+def test_styler_bar_with_NA_values():
+    df1 = DataFrame({"A": [1, 2, NA, 4]})
+    df2 = DataFrame([[NA, NA], [NA, NA]])
+    expected_substring = "style type="
+    html_output1 = df1.style.bar(subset="A").to_html()
+    html_output2 = df2.style.bar(align="left", axis=None).to_html()
+    assert expected_substring in html_output1
+    assert expected_substring in html_output2
+
+
+def test_style_bar_with_pyarrow_NA_values():
+    data = """name,age,test1,test2,teacher
+        Adam,15,95.0,80,Ashby
+        Bob,16,81.0,82,Ashby
+        Dave,16,89.0,84,Jones
+        Fred,15,,88,Jones"""
+    df = read_csv(io.StringIO(data), dtype_backend="pyarrow")
+    expected_substring = "style type="
+    html_output = df.style.bar(subset="test1").to_html()
+    assert expected_substring in html_output