Automatically apply v4 colors in template_defaults future mode

Author: jonmmease

plotly/io/_templates.py

@@ -8,6 +8,10 @@
 import json
 from functools import reduce
 
+from six import string_types
+
+from _plotly_future_ import _future_flags
+
 try:
     from math import gcd
 except ImportError:
@@ -33,7 +37,8 @@ def __init__(self):
         # Initialize built-in templates
         default_templates = ['ggplot2', 'seaborn',
                              'plotly', 'plotly_white',
-                             'plotly_dark', 'presentation', 'xgridoff']
+                             'plotly_dark', 'presentation', 'xgridoff',
+                             'plotly_v4_colors']
 
         for template_name in default_templates:
             self._templates[template_name] = Lazy
@@ -62,6 +67,14 @@ def __getitem__(self, item):
             template_str = pkgutil.get_data('plotly', path).decode('utf-8')
             template_dict = json.loads(template_str)
             template = Template(template_dict)
+
+            if ('template_defaults' in _future_flags
+                    and isinstance(item, string_types)
+                    and item in ('plotly', 'plotly_white', 'plotly_dark')
+            ):
+                template = self.merge_templates(
+                    template, self['plotly_v4_colors'])
+
             self._templates[item] = template
 
         return template