API: deprecation cycle for extra kwargs to linear and symlog scales

tacaswell · tacaswell · commit 4e921b02a01f · 2019-07-25T23:44:39.000-04:00
While log scale became strict about extra kwargs in a patch release in 6357245 (by @tacaswell), I now think that was a mistake. We do want to get to all of the scales raising on unexpected kwargs so deprecate them in 3.2 to raise in 3.3.
diff --git a/doc/api/next_api_changes/2019-07-24-AL.rst b/doc/api/next_api_changes/2019-07-24-AL.rst
@@ -2,4 +2,7 @@ API changes
 ```````````
 
 Passing unsupported keyword arguments to `.ScaleBase` and its subclasses
-`.LinearScale`, `.LogScale`, and `.SymLogScale` now raises a TypeError.
+`.LinearScale`, and `.SymLogScale` is deprecated and will raise a `TypeError` in 3.3.
+
+If extra kwargs are pased to `.LogScale`, `TypeError` will now be
+raised instead of `ValueError`.
diff --git a/lib/matplotlib/scale.py b/lib/matplotlib/scale.py
@@ -19,7 +19,7 @@
     NullLocator, LogLocator, AutoLocator, AutoMinorLocator,
     SymmetricalLogLocator, LogitLocator)
 from matplotlib.transforms import Transform, IdentityTransform
-
+from matplotlib.cbook import warn_deprecated
 
 class ScaleBase:
     """
@@ -39,7 +39,7 @@ class ScaleBase:
 
     """
 
-    def __init__(self, axis):
+    def __init__(self, axis, **kwargs):
         r"""
         Construct a new scale.
 
@@ -52,6 +52,14 @@ def __init__(self, axis):
         be used: a single scale object should be usable by multiple
         `~matplotlib.axis.Axis`\es at the same time.
         """
+        if kwargs:
+            warn_deprecated(
+                '3.2.0',
+                message=(
+                    f"ScaleBase got an unexpected keyword "
+                    f"argument {next(iter(kwargs))!r}. "
+                    'In the future this will raise TypeError')
+            )
 
     def get_transform(self):
         """
@@ -564,8 +572,16 @@ def __init__(self, axis, **kwargs):
             subs = kwargs.pop('subsy', None)
             linscale = kwargs.pop('linscaley', 1.0)
         if kwargs:
-            raise TypeError(f"SymmetricalLogScale got an unexpected keyword "
-                            f"argument {next(iter(kwargs))!r}")
+            warn_deprecated(
+                '3.2.0',
+                message=(
+                    f"SymmetricalLogScale got an unexpected keyword "
+                    f"argument {next(iter(kwargs))!r}. "
+                    'In the future this will raise TypeError')
+            )
+            # raise TypeError(f"SymmetricalLogScale got an unexpected keyword "
+            #                 f"argument {next(iter(kwargs))!r}")
+
         if base <= 1.0:
             raise ValueError("'basex/basey' must be larger than 1")
         if linthresh <= 0.0:
diff --git a/lib/matplotlib/tests/test_scale.py b/lib/matplotlib/tests/test_scale.py
@@ -106,13 +106,18 @@ def test_logscale_mask():
     ax.set(yscale="log")
 
 
-def test_extra_kwargs_raise():
+def test_extra_kwargs_raise_or_warn():
     fig, ax = plt.subplots()
-    with pytest.raises(TypeError):
+
+    # with pytest.raises(TypeError):
+    with pytest.warns(MatplotlibDeprecationWarning):
         ax.set_yscale('linear', nonpos='mask')
+
     with pytest.raises(TypeError):
         ax.set_yscale('log', nonpos='mask')
-    with pytest.raises(TypeError):
+
+    # with pytest.raises(TypeError):
+    with pytest.warns(MatplotlibDeprecationWarning):
         ax.set_yscale('symlog', nonpos='mask')
 
 
