enforce priority of local variable, but fall back on kwarg if the local variable's value is None

alimuldal · alimuldal · commit bb2f30e3f51b · 2015-04-13T15:44:13.000+01:00
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -1141,6 +1141,12 @@ def eventplot(self, positions, orientation='horizontal', lineoffsets=1,
         if len(positions) == 0:
             return []
 
+        # prevent 'singular' keys from **kwargs dict from overriding the effect
+        # of 'plural' keyword arguments (e.g. 'color' overriding 'colors')
+        colors = cbook.kwarg_or_local(kwargs, 'color', colors)
+        linewidths = cbook.kwarg_or_local(kwargs, 'linewidth', linewidths)
+        linestyles = cbook.kwarg_or_local(kwargs, 'linestyle', linestyles)
+
         if not iterable(lineoffsets):
             lineoffsets = [lineoffsets]
         if not iterable(linelengths):
diff --git a/lib/matplotlib/cbook.py b/lib/matplotlib/cbook.py
@@ -658,6 +658,49 @@ def __setstate__(self, state):
         self.extend(state['seq'])
 
 
+class IgnoredKeywordWarning(UserWarning):
+    """
+    A class for issuing warnings about keyword arguments that will be ignored
+    by matplotlib
+    """
+    pass
+
+
+def kwarg_or_local(kwargs, kwarg_name, local_var=None):
+    """
+    Enforces the priority of a local variable over a potentially conflicting
+    argument from a kwargs dict
+
+    Parameters:
+    ------------
+        kwargs: dict
+            Dictionary of keyword arguments; may be modified in place
+
+        kwarg_name: str
+            Name of the keyword argument to process; kwargs[kwarg_name] will be
+            removed in place if it exists
+
+        local_var: any object, optional
+            Local variable
+
+    Returns:
+    ---------
+        out: any object
+            If local_var is None then kwargs[kwarg_name] will be returned,
+            otherwise local_var will be returned and an IgnoredKeywordWarning
+            will be raised
+
+    """
+    kwarg_val = kwargs.pop(kwarg_name, None)
+    if kwarg_val is not None:
+        if local_var is None:
+            return kwarg_val
+        else:
+            warnings.warn('"%s" keyword argument will be ignored' % kwarg_name,
+                          IgnoredKeywordWarning)
+    return local_var
+
+
 def strip_math(s):
     'remove latex formatting from mathtext'
     remove = (r'\mathdefault', r'\rm', r'\cal', r'\tt', r'\it', '\\', '{', '}')
