MNT: deprecate unused numdecs LogLocator param

Author: rcomer

ci/mypy-stubtest-allowlist.txt

@@ -118,6 +118,8 @@ matplotlib.contour.ContourSet.allsegs
 matplotlib.contour.ContourSet.tcolors
 matplotlib.contour.ContourSet.tlinewidths
 matplotlib.figure.FigureBase.get_tightbbox
+matplotlib.ticker.LogLocator.__init__
+matplotlib.ticker.LogLocator.set_params
 
 # positional-only argument name lacking leading underscores
 matplotlib.axes._base._AxesBase.axis

doc/api/next_api_changes/deprecations/25651-REC.rst

@@ -0,0 +1,3 @@
+*numdecs* parameter and attribute of ``LogLocator``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... are deprecated without replacement, because they have no effect.

lib/matplotlib/tests/test_ticker.py

@@ -11,6 +11,7 @@
 import matplotlib as mpl
 import matplotlib.pyplot as plt
 import matplotlib.ticker as mticker
+from matplotlib._api import MatplotlibDeprecationWarning
 
 
 class TestMaxNLocator:
@@ -233,9 +234,11 @@ def test_set_params(self):
         See if change was successful. Should not raise exception.
         """
         loc = mticker.LogLocator()
-        loc.set_params(numticks=7, numdecs=8, subs=[2.0], base=4)
+        with pytest.warns(MatplotlibDeprecationWarning, match="numdecs"):
+            loc.set_params(numticks=7, numdecs=8, subs=[2.0], base=4)
         assert loc.numticks == 7
-        assert loc.numdecs == 8
+        with pytest.warns(MatplotlibDeprecationWarning, match="numdecs"):
+            assert loc.numdecs == 8
         assert loc._base == 4
         assert list(loc._subs) == [2.0]
 

lib/matplotlib/ticker.py

@@ -2244,6 +2244,7 @@ class LogLocator(Locator):
 
     """
 
+    @_api.delete_parameter("3.8", "numdecs")
     def __init__(self, base=10.0, subs=(1.0,), numdecs=4, numticks=None):
         """Place ticks on the locations : subs[j] * base**i."""
         if numticks is None:
@@ -2253,20 +2254,31 @@ def __init__(self, base=10.0, subs=(1.0,), numdecs=4, numticks=None):
                 numticks = 'auto'
         self._base = float(base)
         self._set_subs(subs)
-        self.numdecs = numdecs
+        self._numdecs = numdecs
         self.numticks = numticks
 
+    @_api.delete_parameter("3.8", "numdecs")
     def set_params(self, base=None, subs=None, numdecs=None, numticks=None):
         """Set parameters within this locator."""
         if base is not None:
             self._base = float(base)
         if subs is not None:
             self._set_subs(subs)
         if numdecs is not None:
-            self.numdecs = numdecs
+            self._numdecs = numdecs
         if numticks is not None:
             self.numticks = numticks
 
+    @_api.deprecated("3.8", addendum="This attribute has no effect.")
+    @property
+    def numdecs(self):
+        return self._numdecs
+
+    @_api.deprecated("3.8", addendum="This attribute has no effect.")
+    @numdecs.setter
+    def numdecs(self, numdecs):
+        self._numdecs = numdecs
+
     def _set_subs(self, subs):
         """
         Set the minor ticks for the log scaling every ``base**i*subs[j]``.