Make code match comment in sankey.

anntzer · anntzer · commit 7b0414eaab4b · 2018-08-29T18:58:48.000+02:00
This makes Sankey.add no longer reject a labels that's a *single*
string, consistently with what the docstring states and what the comment
just after implies.

Previously, it would only accept a single string if its length is equal
to the number of flows, in which case it would use one character
of the string for each flow.

Alternatively, we could also change the docstring and delete the comment,
but I think this behavior is more intuitive?  (Not that I ever use
Sankey, though it looks neat...)
diff --git a/doc/api/next_api_changes/2018-08-29-AL-sankey.rst b/doc/api/next_api_changes/2018-08-29-AL-sankey.rst
@@ -0,0 +1,9 @@
+Passing a single string as *labels* to `Sankey.add`
+```````````````````````````````````````````````````
+
+Previously, `Sankey.add` would only accept a single string as the *labels*
+argument if its length is equal to the number of flows, in which case it would
+use one character of the string for each flow.
+
+The behavior has been changed to match the documented one: when a single string
+is passed, it is used to label all the flows.
diff --git a/lib/matplotlib/sankey.py b/lib/matplotlib/sankey.py
@@ -10,7 +10,7 @@
 from matplotlib.path import Path
 from matplotlib.patches import PathPatch
 from matplotlib.transforms import Affine2D
-from matplotlib import docstring
+from matplotlib import cbook, docstring
 from matplotlib import rcParams
 
 _log = logging.getLogger(__name__)
@@ -449,11 +449,8 @@ def add(self, patchlabel='', flows=None, orientations=None, labels='',
             "orientations and flows must have the same length.\n"
             "orientations has length %d, but flows has length %d."
             % (len(orientations), n))
-        if labels != '' and getattr(labels, '__iter__', False):
-            # np.iterable() isn't used because it would give True if labels is
-            # a string
-            if len(labels) != n:
-                raise ValueError(
+        if not cbook.is_scalar_or_string(labels) and len(labels) != n:
+            raise ValueError(
                 "If labels is a list, then labels and flows must have the "
                 "same length.\nlabels has length %d, but flows has length %d."
                 % (len(labels), n))
