added default argument to ChoiceBlock.

If default is not None and required is True,
don't render a blank option.

CHANGELOG.txt

@@ -5,6 +5,7 @@ Changelog
 ~~~~~~~~~~~~~~~~
 
  * View live / draft links in the admin now consistently open in a new window (Marco Fucci)
+ * `ChoiceBlock` now omits the blank option if the block is required and has a default value (Andreas Nüßlein)
 
 
 1.8 (15.12.2016)

CONTRIBUTORS.rst

@@ -197,6 +197,7 @@ Contributors
 * Mihail Russu
 * Robert Slotboom
 * Erick M'bwana
+* Andreas Nüßlein
 
 Translators
 ===========

wagtail/wagtailcore/blocks/field_block.py

@@ -333,7 +333,7 @@ class ChoiceBlock(FieldBlock):
 
     choices = ()
 
-    def __init__(self, choices=None, required=True, help_text=None, **kwargs):
+    def __init__(self, choices=None, default=None, required=True, help_text=None, **kwargs):
         if choices is None:
             # no choices specified, so pick up the choice defined at the class level
             choices = self.choices
@@ -361,14 +361,18 @@ class ChoiceBlock(FieldBlock):
         # one already. We have to do this at render time in the case of callable choices - so rather
         # than having separate code paths for static vs dynamic lists, we'll _always_ pass a callable
         # to ChoiceField to perform this step at render time.
-        callable_choices = self.get_callable_choices(choices)
-        self.field = forms.ChoiceField(choices=callable_choices, required=required, help_text=help_text)
-        super(ChoiceBlock, self).__init__(**kwargs)
 
-    def get_callable_choices(self, choices):
+        # If we have a default choice and the field is required, we don't need to add a blank option.
+        callable_choices = self.get_callable_choices(choices, blank_choice=not(default and required))
+
+        self.field = forms.ChoiceField(choices=callable_choices, required=required, help_text=help_text)
+        super(ChoiceBlock, self).__init__(default=default, **kwargs)
+
+    def get_callable_choices(self, choices, blank_choice=True):
         """
         Return a callable that we can pass into `forms.ChoiceField`, which will provide the
-        choices list with the addition of a blank choice (if one does not already exist).
+        choices list with the addition of a blank choice (if blank_choice=True and one does not
+        already exist).
         """
         def choices_callable():
             # Variable choices could be an instance of CallableChoiceIterator, which may be wrapping
@@ -377,7 +381,11 @@ class ChoiceBlock(FieldBlock):
             # once while rendering the final ChoiceField).
             local_choices = list(choices)
 
-            # If choices does not already contain a blank option, insert one
+            # If blank_choice=False has been specified, return the choices list as is
+            if not blank_choice:
+                return local_choices
+
+            # Else: if choices does not already contain a blank option, insert one
             # (to match Django's own behaviour for modelfields:
             # https://github.com/django/django/blob/1.7.5/django/db/models/fields/__init__.py#L732-744)
             has_blank_choice = False

wagtail/wagtailcore/tests/test_blocks.py

@@ -426,6 +426,15 @@ class TestChoiceBlock(unittest.TestCase):
         self.assertIn('<option value="tea">Tea</option>', html)
         self.assertIn('<option value="coffee" selected="selected">Coffee</option>', html)
 
+    def test_render_required_choice_block_with_default(self):
+        block = blocks.ChoiceBlock(choices=[('tea', 'Tea'), ('coffee', 'Coffee')], default='tea')
+        html = block.render_form('coffee', prefix='beverage')
+        self.assertIn('<select id="beverage" name="beverage" placeholder="">', html)
+        # blank option should NOT be rendered if default and required are set.
+        self.assertNotIn('<option value="">%s</option>' % self.blank_choice_dash_label, html)
+        self.assertIn('<option value="tea">Tea</option>', html)
+        self.assertIn('<option value="coffee" selected="selected">Coffee</option>', html)
+
     def test_render_required_choice_block_with_callable_choices(self):
         def callable_choices():
             return [('tea', 'Tea'), ('coffee', 'Coffee')]