Fix #7722.

Render BooleanFields with allow_null=True as HTML select rather than as
HTML checkbox in Browsable API #7722.

docs/topics/html-and-forms.md

@@ -215,6 +215,7 @@ select.html | `ChoiceField` or relational field types | hide_label
 radio.html | `ChoiceField` or relational field types | inline, hide_label
 select_multiple.html | `MultipleChoiceField` or relational fields with `many=True` | hide_label
 checkbox_multiple.html | `MultipleChoiceField` or relational fields with `many=True` | inline, hide_label
-checkbox.html | `BooleanField` | hide_label
+checkbox.html | `BooleanField` with `allow_null=False` | hide_label
+select_boolean.html | `BooleanField` with `allow_null=True` | hide_label
 fieldset.html | Nested serializer | hide_label
 list_fieldset.html | `ListField` or nested serializer with `many=True` |   hide_label

rest_framework/fields.py

@@ -720,6 +720,10 @@ class BooleanField(Field):
     }
     NULL_VALUES = {'null', 'Null', 'NULL', '', None}
 
+    @property
+    def _is_nullable_boolean_field(self):
+        return self.allow_null
+
     def to_internal_value(self, data):
         try:
             if data in self.TRUE_VALUES:
@@ -741,6 +745,14 @@ class BooleanField(Field):
             return None
         return bool(value)
 
+    def iter_options(self):
+        choices = {
+            "": _("Unknown"),
+            True: _("Yes"),
+            False: _("No"),
+        }
+        return iter_options(choices)
+
 
 class NullBooleanField(BooleanField):
     initial = None

rest_framework/renderers.py

@@ -329,6 +329,9 @@ class HTMLFormRenderer(BaseRenderer):
         if isinstance(field._field, serializers.HiddenField):
             return ''
 
+        if isinstance(field._field, serializers.BooleanField) and field._field.allow_null:
+            style = {'base_template': 'select_boolean.html'}
+        else:
             style = self.default_style[field].copy()
         style.update(field.style)
         if 'template_pack' not in style:

rest_framework/templates/rest_framework/horizontal/select_boolean.html

@@ -0,0 +1,25 @@
+
+<div class="form-group">
+  {% if field.label %}
+    <label class="col-sm-2 control-label {% if style.hide_label %}sr-only{% endif %}">
+      {{ field.label }}
+    </label>
+  {% endif %}
+
+  <div class="col-sm-10">
+    <select class="form-control" name="{{ field.name }}">
+        {% for select in field.iter_options %}
+            <option value="{{ select.value }}" {% if select.value == field.value %}selected{% endif %}>{{ select.display_text }}</option>
+        {% endfor %}
+    </select>
+    {% if field.errors %}
+      {% for error in field.errors %}
+        <span class="help-block">{{ error }}</span>
+      {% endfor %}
+    {% endif %}
+
+    {% if field.help_text %}
+      <span class="help-block">{{ field.help_text|safe }}</span>
+    {% endif %}
+  </div>
+</div>

rest_framework/templates/rest_framework/inline/select_boolean.html

@@ -0,0 +1,15 @@
+{% load rest_framework %}
+
+<div class="form-group {% if field.errors %}has-error{% endif %}">
+  {% if field.label %}
+    <label class="sr-only">
+      {{ field.label }}
+    </label>
+  {% endif %}
+
+  <select class="form-control" name="{{ field.name }}">
+    {% for select in field.iter_options %}
+        <option value="{{ select.value }}" {% if select.value|as_string == field.value|as_string %}selected{% endif %} >{{ select.display_text }}</option>
+    {% endfor %}
+  </select>
+</div>

rest_framework/templates/rest_framework/vertical/select_boolean.html

@@ -0,0 +1,23 @@
+<div class="form-group {% if field.errors %}has-error{% endif %}">
+  {% if field.label %}
+    <label {% if style.hide_label %}class="sr-only"{% endif %}>
+      {{ field.label }}
+    </label>
+  {% endif %}
+
+  <select class="form-control" name="{{ field.name }}">
+    {% for select in field.iter_options %}
+    <option value="{{ select.value }}" {% if select.value == field.value %}selected{% endif %}>{{ select.display_text }}</option>
+    {% endfor %}
+  </select>
+
+  {% if field.errors %}
+    {% for error in field.errors %}
+      <span class="help-block">{{ error }}</span>
+    {% endfor %}
+  {% endif %}
+
+  {% if field.help_text %}
+    <span class="help-block">{{ field.help_text|safe }}</span>
+  {% endif %}
+</div>

rest_framework/utils/serializer_helpers.py

@@ -76,6 +76,9 @@ class BoundField:
         )
 
     def as_form_field(self):
+        if getattr(self._field, '_is_nullable_boolean_field', False):
+            value = '' if self.value is None else self.value
+        else:
             value = '' if (self.value is None or self.value is False) else self.value
         return self.__class__(self._field, value, self.errors, self._prefix)
 
@@ -129,6 +132,8 @@ class NestedBoundField(BoundField):
         for key, value in self.value.items():
             if isinstance(value, (list, dict)):
                 values[key] = value
+            elif getattr(self.fields[key], '_is_nullable_boolean_field', False):
+                values[key] = '' if value is None else value
             else:
                 values[key] = '' if (value is None or value is False) else force_str(value)
         return self.__class__(self._field, values, self.errors, self._prefix)

tests/test_bound_fields.py

@@ -1,3 +1,4 @@
+import pytest
 from django.http import QueryDict
 
 from rest_framework import serializers
@@ -59,11 +60,13 @@ class TestSimpleBoundField:
     def test_as_form_fields(self):
         class ExampleSerializer(serializers.Serializer):
             bool_field = serializers.BooleanField()
+            nullable_bool_field = serializers.BooleanField(allow_null=True)
             null_field = serializers.IntegerField(allow_null=True)
 
-        serializer = ExampleSerializer(data={'bool_field': False, 'null_field': None})
+        serializer = ExampleSerializer(data={'bool_field': False, 'nullable_bool_field': False, 'null_field': None})
         assert serializer.is_valid()
         assert serializer['bool_field'].as_form_field().value == ''
+        assert serializer['nullable_bool_field'].as_form_field().value is False
         assert serializer['null_field'].as_form_field().value == ''
 
     def test_rendering_boolean_field(self):
@@ -90,6 +93,55 @@ class TestSimpleBoundField:
         rendered_packed = ''.join(rendered.split())
         assert rendered_packed == expected_packed
 
+    @pytest.mark.parametrize('bool_field_value', [True, False, None])
+    def test_rendering_nullable_boolean_field(self, bool_field_value):
+        from rest_framework.renderers import HTMLFormRenderer
+
+        class ExampleSerializer(serializers.Serializer):
+            bool_field = serializers.BooleanField(
+                allow_null=True,
+                style={'base_template': 'select_boolean.html', 'template_pack': 'rest_framework/vertical'})
+
+        serializer = ExampleSerializer(data={'bool_field': bool_field_value})
+        assert serializer.is_valid()
+        renderer = HTMLFormRenderer()
+        rendered = renderer.render_field(serializer['bool_field'], {})
+        if bool_field_value is True:
+            expected_packed = (
+                '<divclass="form-group">'
+                '<label>Boolfield</label>'
+                '<selectclass="form-control"name="bool_field">'
+                '<optionvalue="">Unknown</option>'
+                '<optionvalue="True"selected>Yes</option>'
+                '<optionvalue="False">No</option>'
+                '</select>'
+                '</div>'
+            )
+        elif bool_field_value is False:
+            expected_packed = (
+                '<divclass="form-group">'
+                '<label>Boolfield</label>'
+                '<selectclass="form-control"name="bool_field">'
+                '<optionvalue="">Unknown</option>'
+                '<optionvalue="True">Yes</option>'
+                '<optionvalue="False"selected>No</option>'
+                '</select>'
+                '</div>'
+            )
+        elif bool_field_value is None:
+            expected_packed = (
+                '<divclass="form-group">'
+                '<label>Boolfield</label>'
+                '<selectclass="form-control"name="bool_field">'
+                '<optionvalue=""selected>Unknown</option>'
+                '<optionvalue="True">Yes</option>'
+                '<optionvalue="False">No</option>'
+                '</select>'
+                '</div>'
+            )
+        rendered_packed = ''.join(rendered.split())
+        assert rendered_packed == expected_packed
+
 
 class CustomJSONField(serializers.JSONField):
     pass
@@ -120,6 +172,7 @@ class TestNestedBoundField:
     def test_as_form_fields(self):
         class Nested(serializers.Serializer):
             bool_field = serializers.BooleanField()
+            nullable_bool_field = serializers.BooleanField(allow_null=True)
             null_field = serializers.IntegerField(allow_null=True)
             json_field = serializers.JSONField()
             custom_json_field = CustomJSONField()
@@ -129,12 +182,13 @@ class TestNestedBoundField:
 
         serializer = ExampleSerializer(
             data={'nested': {
-                'bool_field': False, 'null_field': None,
+                'bool_field': False, 'nullable_bool_field': False, 'null_field': None,
                 'json_field': {'bool_item': True, 'number': 1, 'text_item': 'text'},
                 'custom_json_field': {'bool_item': True, 'number': 1, 'text_item': 'text'},
             }})
         assert serializer.is_valid()
         assert serializer['nested']['bool_field'].as_form_field().value == ''
+        assert serializer['nested']['nullable_bool_field'].as_form_field().value is False
         assert serializer['nested']['null_field'].as_form_field().value == ''
         assert serializer['nested']['json_field'].as_form_field().value == '''{
     "bool_item": true,

tests/test_fields.py

@@ -364,6 +364,8 @@ class TestBooleanHTMLInput:
         """
         HTML checkboxes do not send any value, but should be treated
         as `False` by BooleanField.
+        Note: BooleanFields are rendered as HTML checkboxes
+        only if allow_null=False.
         """
         class TestSerializer(serializers.Serializer):
             archived = serializers.BooleanField()
@@ -376,6 +378,8 @@ class TestBooleanHTMLInput:
         """
         HTML checkboxes do not send any value, but should be treated
         as `False` by BooleanField, even if the field is required=False.
+        Note: BooleanFields are rendered as HTML checkboxes
+        only if allow_null=False.
         """
         class TestSerializer(serializers.Serializer):
             archived = serializers.BooleanField(required=False)
@@ -384,6 +388,22 @@ class TestBooleanHTMLInput:
         assert serializer.is_valid()
         assert serializer.validated_data == {'archived': False}
 
+    @pytest.mark.parametrize(('select_option_value', 'expected_internal_value'), (('', None), ('True', True), ('False', False)))
+    def test_nullable_boolean_html(self, select_option_value, expected_internal_value):
+        """
+        If allow_null=True, BooleanField is rendered as HTML select element
+        containing three option elements with values '', 'True', and 'False'.
+        If option value=False selected, the internal value False is expected.
+        If option value=True selected, the internal value True is expected.
+        If option value= (the empty string) selected, the internal value None is expected.
+        """
+        class TestSerializer(serializers.Serializer):
+            archived = serializers.BooleanField(allow_null=True)
+
+        serializer = TestSerializer(data=QueryDict('archived={}'.format(select_option_value)))
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'archived': expected_internal_value}
+
 
 class TestHTMLInput:
     def test_empty_html_charfield_with_default(self):