MNT: fixes from code review.

tacaswell · timhoffm · web-flow · commit 50c397a56f16 · 2024-04-05T17:31:21.000-04:00
Co-authored-by: Tim Hoffmann &lt;2836374+timhoffm@users.noreply.github.com&gt;
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -7201,7 +7201,7 @@ def stairs(self, values, edges=None, *,
 
             Passing both ``fill=True` and ``baseline=None`` will likely result in
             undesired filling as the first and last points will be connected
-            with a straight line with the fill between and the stairs.
+            with a straight line with the fill between the line and the stairs.
 
 
         Returns
@@ -7244,6 +7244,7 @@ def stairs(self, values, edges=None, *,
         if baseline is None and fill:
             _api.warn_external(
                 f"Both {baseline=} and {fill=} have been passed. "
+                "baseline=None is only intended for unfilled stair plots. "
                 "Because baseline in None, the Path used to draw the stairs will "
                 "not be closed, thus because fill is True the polygon will be closed "
                 "by drawing an (unstroked) edge from the first to last point.  It is "
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -2344,18 +2344,13 @@ def test_hist_zorder(histtype, zorder):
 
 def test_stairs_no_baseline_fill_warns():
     fig, ax = plt.subplots()
-    baseline = None
-    fill = True
-    warn_match = (
-        "Because baseline in None, the Path used to draw the stairs will "
-    )
-    with pytest.warns(UserWarning, match=warn_match):
+    with pytest.warns(UserWarning, match="baseline=None and fill=True"):
         ax.stairs(
             [4, 5, 1, 0, 2],
             [1, 2, 3, 4, 5, 6],
             facecolor="blue",
-            baseline=baseline,
-            fill=fill
+            baseline=None,
+            fill=True
         )
 
 
