Apply suggestions from timhoffm code review

Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

Author: rcomer

lib/matplotlib/axes/_axes.py

@@ -3194,9 +3194,15 @@ def grouped_bar(self, heights, *, positions=None, group_spacing=1.5, bar_spacing
 
         **kwargs : `.Rectangle` properties
 
-            The following properties additionally accept a sequence of values
-            corresponding to the datasets in *heights*:
-            *edgecolor*, *facecolor*, *linewidth*, *linestyle*, *hatch*.
+            Properties applied to all bars. The following properties additionally
+            accept a sequence of values corresponding to the datasets in
+            *heights*:
+            
+            - *edgecolor*
+            - *facecolor*
+            - *linewidth*
+            - *linestyle*
+            - *hatch*
 
             %(Rectangle:kwdoc)s
 

lib/matplotlib/tests/test__style_helpers.py

@@ -11,6 +11,7 @@
                                         ('linestyle', ["-", "--", ":"]),
                                         ('linewidth', [1, 1.5, 2])])
 def test_style_generator_list(key, value):
+    """Test that style parameter lists are distributed to the generator."""
     kw = {'foo': 12, key: value}
     new_kw, gen = style_generator(kw)
 
@@ -33,6 +34,7 @@ def test_style_generator_list(key, value):
                                         ('linestyle', "-"),
                                         ('linewidth', 1)])
 def test_style_generator_single(key, value):
+    """Test that single-value style parameters are distributed to the generator."""
     kw = {'foo': 12, key: value}
     new_kw, gen = style_generator(kw)
 
@@ -48,13 +50,17 @@ def test_style_generator_single(key, value):
 
 
 @pytest.mark.parametrize('key', ['facecolor', 'hatch', 'linestyle'])
-def test_style_generator_empty(key):
+def test_style_generator_raises_on_empty_style_parameter_list(key):
     kw = {key: []}
     with pytest.raises(TypeError, match=f'{key} must not be an empty sequence'):
         style_generator(kw)
 
 
 def test_style_generator_sequence_type_styles():
+    """
+    Test that sequence type style values are detected as single value
+    and passed to a all elements of the generator.
+    """
     kw = {'facecolor':  ('r', 0.5),
           'edgecolor': [0.5, 0.5, 0.5],
           'linestyle': (0, (1, 1))}

lib/matplotlib/tests/test_axes.py

@@ -3450,18 +3450,18 @@ def test_stackplot_facecolor():
     y1 = 1.0 * x
     y2 = 2.0 * x + 1
 
-    fcols = ['r', 'b']
+    facecolors = ['r', 'b']
 
     fig, ax = plt.subplots()
 
-    colls = ax.stackplot(x, y1, y2, facecolor=fcols, colors=['c', 'm'])
-    for coll, fcol in zip(colls, fcols):
-        assert mcolors.same_color(coll.get_facecolor(), fcol)
+    colls = ax.stackplot(x, y1, y2, facecolor=facecolors, colors=['c', 'm'])
+    for coll, fcol in zip(colls, facecolors):
+        assert mcolors.same_color(coll.get_facecolor(), facecolors)
 
     # Plural alias should also work
-    colls = ax.stackplot(x, y1, y2, facecolors=fcols, colors=['c', 'm'])
-    for coll, fcol in zip(colls, fcols):
-        assert mcolors.same_color(coll.get_facecolor(), fcol)
+    colls = ax.stackplot(x, y1, y2, facecolors=facecolors, colors=['c', 'm'])
+    for coll, fcol in zip(colls, facecolors):
+        assert mcolors.same_color(coll.get_facecolor(), facecolors)
 
 
 def test_stackplot_subfig_legend():