Don't override errorbar caps with 'lines.markeredgecolor' rcParam (matplotlib#29895)

* Fix matplotlib#29780 : color of errorbar caps affected by markeredgecolor
To solve this, we needed to ensure that the caps would use the
specified ecolor independently of the global
mpl.rcParams['lines.markeredgecolor']. This was achieved by
setting the marker edge color for the caps separately, rather
 than relying on the global configuration.

* Taking whitespaces

* Update lib/matplotlib/tests/test_axes.py

* Update lib/matplotlib/tests/test_axes.py

Co-authored-by: Tim Hoffmann <[email protected]>

* Alteration of the tests

---------

Co-authored-by: Tim Hoffmann <[email protected]>

Author: useidemaisachola

lib/matplotlib/axes/_axes.py

@@ -3739,7 +3739,7 @@ def _upcast_err(err):
                     'zorder', 'rasterized'):
             if key in kwargs:
                 eb_cap_style[key] = kwargs[key]
-        eb_cap_style['color'] = ecolor
+        eb_cap_style["markeredgecolor"] = ecolor
 
         barcols = []
         caplines = {'x': [], 'y': []}

lib/matplotlib/tests/test_axes.py

@@ -9741,6 +9741,34 @@ def test_bar_shape_mismatch():
         plt.bar(x, height)
 
 
+def test_caps_color():
+
+    # Creates a simple plot with error bars and a specified ecolor
+    x = np.linspace(0, 10, 10)
+    mpl.rcParams['lines.markeredgecolor'] = 'green'
+    ecolor = 'red'
+
+    fig, ax = plt.subplots()
+    errorbars = ax.errorbar(x, np.sin(x), yerr=0.1, ecolor=ecolor)
+
+    # Tests if the caps have the specified color
+    for cap in errorbars[2]:
+        assert mcolors.same_color(cap.get_edgecolor(), ecolor)
+
+
+def test_caps_no_ecolor():
+
+    # Creates a simple plot with error bars without specifying ecolor
+    x = np.linspace(0, 10, 10)
+    mpl.rcParams['lines.markeredgecolor'] = 'green'
+    fig, ax = plt.subplots()
+    errorbars = ax.errorbar(x, np.sin(x), yerr=0.1)
+
+    # Tests if the caps have the default color (blue)
+    for cap in errorbars[2]:
+        assert mcolors.same_color(cap.get_edgecolor(), "blue")
+
+
 def test_pie_non_finite_values():
     fig, ax = plt.subplots()
     df = [5, float('nan'), float('inf')]