Merge pull request matplotlib#21074 from anntzer/msn2

Deprecate MarkerStyle(None).

Author: timhoffm

doc/api/next_api_changes/deprecations/21056-AL.rst

@@ -1,3 +1,3 @@
-Calling ``MarkerStyle()`` with no arguments
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Calling ``MarkerStyle()`` with no arguments or ``MarkerStyle(None)``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ... is deprecated; use ``MarkerStyle("")`` to construct an empty marker style.

lib/matplotlib/lines.py

@@ -368,6 +368,8 @@ def __init__(self, xdata, ydata,
 
         self._color = None
         self.set_color(color)
+        if marker is None:
+            marker = 'none'  # Default.
         self._marker = MarkerStyle(marker, fillstyle)
 
         self._markevery = None

lib/matplotlib/markers.py

@@ -64,9 +64,10 @@
                                       rotated by ``angle``.
 ============================== ====== =========================================
 
-``None`` also means 'nothing' when directly constructing a `.MarkerStyle`, but
-note that there are other contexts where ``marker=None`` instead means "the
-default marker" (e.g. :rc:`scatter.marker` for `.Axes.scatter`).
+As a deprecated feature, ``None`` also means 'nothing' when directly
+constructing a `.MarkerStyle`, but note that there are other contexts where
+``marker=None`` instead means "the default marker" (e.g. :rc:`scatter.marker`
+for `.Axes.scatter`).
 
 Note that special symbols can be defined via the
 :doc:`STIX math font </tutorials/text/mathtext>`,
@@ -202,7 +203,6 @@ class MarkerStyle:
         CARETDOWNBASE: 'caretdownbase',
         "None": 'nothing',
         "none": 'nothing',
-        None: 'nothing',
         ' ': 'nothing',
         '': 'nothing'
     }
@@ -245,6 +245,12 @@ def __init__(self, marker=_unset, fillstyle=None):
                 "deprecated since %(since)s; support will be removed "
                 "%(removal)s.  Use MarkerStyle('') to construct an empty "
                 "MarkerStyle.")
+        if marker is None:
+            marker = ""
+            _api.warn_deprecated(
+                "3.6", message="MarkerStyle(None) is deprecated since "
+                "%(since)s; support will be removed %(removal)s.  Use "
+                "MarkerStyle('') to construct an empty MarkerStyle.")
         self._set_marker(marker)
 
     __init__.__signature__ = inspect.signature(  # Only for deprecation period.

lib/matplotlib/tests/test_axes.py

@@ -4117,9 +4117,15 @@ def test_eventplot_orientation(data, orientation):
 @image_comparison(['marker_styles.png'], remove_text=True)
 def test_marker_styles():
     fig, ax = plt.subplots()
-    for y, marker in enumerate(sorted(
-            {*matplotlib.markers.MarkerStyle.markers} - {"none"},
-            key=lambda x: str(type(x))+str(x))):
+    # Since generation of the test image, None was removed but 'none' was
+    # added. By moving 'none' to the front (=former sorted place of None)
+    # we can avoid regenerating the test image. This can be removed if the
+    # test image has to be regenerated for other reasons.
+    markers = sorted(matplotlib.markers.MarkerStyle.markers,
+                     key=lambda x: str(type(x))+str(x))
+    markers.remove('none')
+    markers = ['none', *markers]
+    for y, marker in enumerate(markers):
         ax.plot((y % 2)*5 + np.arange(10)*10, np.ones(10)*10*y, linestyle='',
                 marker=marker, markersize=10+y/5, label=marker)
 

lib/matplotlib/tests/test_marker.py

@@ -19,7 +19,6 @@ def test_marker_fillstyle():
     'x',
     '',
     'None',
-    None,
     r'$\frac{1}{2}$',
     "$\u266B$",
     1,
@@ -40,10 +39,13 @@ def test_markers_valid(marker):
     markers.MarkerStyle(marker)
 
 
-def test_deprecated_marker_noargs():
+def test_deprecated_marker():
     with pytest.warns(MatplotlibDeprecationWarning):
         ms = markers.MarkerStyle()
     markers.MarkerStyle(ms)  # No warning on copy.
+    with pytest.warns(MatplotlibDeprecationWarning):
+        ms = markers.MarkerStyle(None)
+    markers.MarkerStyle(ms)  # No warning on copy.
 
 
 @pytest.mark.parametrize('marker', [