Use None as a sentinel value for unmodified axes.hold in rcParams.

efiring · efiring · commit 219ce30113c8 · 2016-11-26T15:43:07.000-10:00
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -870,8 +870,13 @@ def matplotlib_fname():
     }
 
 _obsolete_set = set(['tk.pythoninspect', 'legend.isaxes'])
+
+# The following may use a value of None to suppress the warning.
+_deprecated_set = set(['axes.hold'])  # do NOT include in _all_deprecated
+
 _all_deprecated = set(chain(_deprecated_ignore_map,
-                            _deprecated_map, _obsolete_set))
+                            _deprecated_map,
+                            _obsolete_set))
 
 
 class RcParams(dict):
@@ -887,6 +892,8 @@ class RcParams(dict):
                     six.iteritems(defaultParams)
                     if key not in _all_deprecated)
     msg_depr = "%s is deprecated and replaced with %s; please use the latter."
+    msg_depr_set = ("%s is deprecated. Please remove it from your "
+                    "matplotlibrc and/or style files.")
     msg_depr_ignore = "%s is deprecated and ignored. Use %s"
     msg_obsolete = ("%s is obsolete. Please remove it from your matplotlibrc "
                     "and/or style files.")
@@ -903,6 +910,8 @@ def __setitem__(self, key, val):
                 warnings.warn(self.msg_depr % (key, alt_key))
                 key = alt_key
                 val = alt_val(val)
+            elif key in _deprecated_set and val is not None:
+                warnings.warn(self.msg_depr_set % key)
             elif key in _deprecated_ignore_map:
                 alt = _deprecated_ignore_map[key]
                 warnings.warn(self.msg_depr_ignore % (key, alt))
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -540,6 +540,9 @@ def __init__(self, fig, rect,
         self._rasterization_zorder = None
 
         self._hold = rcParams['axes.hold']
+        if self._hold is None:
+            self._hold = True
+
         self._connected = {}  # a dict from events to (id, func)
         self.cla()
         # funcs used to format x and y - fall back on major formatters
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -342,6 +342,9 @@ def __init__(self,
         self.patch.set_aa(False)
 
         self._hold = rcParams['axes.hold']
+        if self._hold is None:
+            self._hold = True
+
         self.canvas = None
         self._suptitle = None
 
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -147,7 +147,8 @@ def validate_bool_maybe_none(b):
 
 def deprecate_axes_hold(value):
     if value is None:
-        return True
+        return None  # converted to True where accessed in figure.py,
+                     # axes/_base.py
     warnings.warn("axes.hold is deprecated, will be removed in 3.0")
     return validate_bool(value)
 
