Fix ColorScale presentation when specified as string (#1089)

* Added tests for colorscales specified as a string

Added tests checking that a colorscale specified as a string is returned correctly. Previously it had been returned as a tuple of 1-tuples. e.g. "Viridis" -> (('V',), ('i',), ('r',), ('i',), ('d',), ('i',), ('s',)). Catches #1087.

* Fix presentation of string colorscales

Fixes #1087.

* Added support for Cividis to ColorScaleValidator

Author: ivirshup

_plotly_utils/basevalidators.py

@@ -1211,7 +1211,7 @@ class ColorscaleValidator(BaseValidator):
     named_colorscales = [
         'Greys', 'YlGnBu', 'Greens', 'YlOrRd', 'Bluered', 'RdBu', 'Reds',
         'Blues', 'Picnic', 'Rainbow', 'Portland', 'Jet', 'Hot', 'Blackbody',
-        'Earth', 'Electric', 'Viridis'
+        'Earth', 'Electric', 'Viridis', 'Cividis'
     ]
 
     def __init__(self, plotly_name, parent_name, **kwargs):
@@ -1229,7 +1229,7 @@ def description(self):
       - One of the following named colorscales:
             ['Greys', 'YlGnBu', 'Greens', 'YlOrRd', 'Bluered', 'RdBu',
             'Reds', 'Blues', 'Picnic', 'Rainbow', 'Portland', 'Jet',
-            'Hot', 'Blackbody', 'Earth', 'Electric', 'Viridis']
+            'Hot', 'Blackbody', 'Earth', 'Electric', 'Viridis', 'Cividis]
         """.format(plotly_name=self.plotly_name)
 
         return desc
@@ -1274,9 +1274,11 @@ def validate_coerce(self, v):
         return v
 
     def present(self, v):
-        # Return tuple of tuples so that colorscale is immutable
+        # Return-type must be immutable
         if v is None:
             return None
+        elif isinstance(v, string_types):
+            return v
         else:
             return tuple([tuple(e) for e in v])
 

_plotly_utils/tests/validators/test_colorscale_validator.py

@@ -11,7 +11,8 @@ def validator():
 
 
 @pytest.fixture(params=['Greys', 'YlGnBu', 'Greens', 'YlOrRd', 'Bluered', 'RdBu', 'Reds', 'Blues',
-                        'Picnic', 'Rainbow', 'Portland', 'Jet', 'Hot', 'Blackbody', 'Earth', 'Electric', 'Viridis'])
+                        'Picnic', 'Rainbow', 'Portland', 'Jet', 'Hot', 'Blackbody', 'Earth', 'Electric', 
+                        'Viridis', 'Cividis'])
 def named_colorscale(request):
     return request.param
 
@@ -26,6 +27,8 @@ def test_acceptance_named(named_colorscale, validator: ColorscaleValidator):
     # Uppercase
     assert (validator.validate_coerce(named_colorscale.upper()) ==
            named_colorscale.upper())
+    
+    assert validator.present(named_colorscale) == named_colorscale
 
 # ### Acceptance as array ###
 @pytest.mark.parametrize('val', [

plotly/tests/test_core/test_graph_objs/test_properties_validated.py

@@ -102,6 +102,16 @@ def test_present_colorscale(self):
         # Presented as tuple of tuples
         self.assertEqual(self.scatter.marker.colorscale,
                          ((0, 'red'), (1, 'green')))
+    
+    def test_present_colorscale_str(self):
+        self.assertIsNone(self.scatter.marker.colorscale)
+
+        # Assign string
+        self.scatter.marker.colorscale = "Viridis"
+
+        # Presented as a string
+        self.assertEqual(self.scatter.marker.colorscale,
+                         "Viridis")
 
 
 class TestPropertyIterContains(TestCase):