Fix autolevels with SymLogNorm when base is not provided

Author: lukelbd

proplot/axes/plot.py

@@ -30,7 +30,14 @@
 from .. import constructor
 from ..config import rc
 from ..internals import ic  # noqa: F401
-from ..internals import _dummy_context, _not_none, _state_context, docstring, warnings
+from ..internals import (
+    _dummy_context,
+    _flexible_getattr,
+    _not_none,
+    _state_context,
+    docstring,
+    warnings,
+)
 from ..utils import edges, edges2d, to_rgb, to_xyz, units
 
 try:
@@ -2672,7 +2679,8 @@ def _auto_levels_locator(
     elif isinstance(norm, mcolors.LogNorm):
         level_locator = tick_locator = mticker.LogLocator(**locator_kw)
     elif isinstance(norm, mcolors.SymLogNorm):
-        locator_kw.setdefault('linthresh', norm.linthresh)
+        locator_kw.setdefault('base', _flexible_getattr(norm, 'base', 10))
+        locator_kw.setdefault('linthresh', _flexible_getattr(norm, 'linthresh', 1))
         level_locator = tick_locator = mticker.SymmetricalLogLocator(**locator_kw)
     else:
         nbins = N * 2 if positive or negative else N

proplot/internals/__init__.py

@@ -18,6 +18,19 @@
     ic = lambda *a: None if not a else (a[0] if len(a) == 1 else a)  # noqa
 
 
+def _flexible_getattr(obj, attr, default=None):
+    """
+    Search for attribute ``attr`` and ``_attr``. This guards against simple
+    upstream matplotlib changes.
+    """
+    if hasattr(obj, attr) and hasattr(obj, '_' + attr):
+        warnings._warn_proplot(
+            f"Object {obj!r} has both {attr!r} and {'_' + attr!r} attributes."
+            'Using former.'
+        )
+    return getattr(obj, attr, getattr(obj, '_' + attr, default))
+
+
 def _not_none(*args, default=None, **kwargs):
     """
     Return the first non-``None`` value. This is used with keyword arg aliases and