Add --- null option for selects. Closes #2096.

rest_framework/templates/rest_framework/horizontal/select.html

@@ -4,6 +4,9 @@
     {% endif %}
     <div class="col-sm-10">
         <select class="form-control" name="{{ field.name }}">
+        {% if field.allow_null %}
+            <option value="" {% if not field.value %}selected{% endif %}>--------</option>
+        {% endif %}
         {% for key, text in field.choices.items %}
             <option value="{{ key }}" {% if key == field.value %}selected{% endif %}>{{ text }}</option>
         {% endfor %}

rest_framework/templates/rest_framework/inline/select.html

@@ -3,8 +3,11 @@
         <label class="sr-only">{{ field.label }}</label>
     {% endif %}
     <select class="form-control" name="{{ field.name }}">
+        {% if field.allow_null %}
+            <option value="" {% if not field.value %}selected{% endif %}>--------</option>
+        {% endif %}
         {% for key, text in field.choices.items %}
-        <option value="{{ key }}" {% if key == field.value %}selected{% endif %}>{{ text }}</option>
+            <option value="{{ key }}" {% if key == field.value %}selected{% endif %}>{{ text }}</option>
         {% endfor %}
     </select>
 </div>

rest_framework/templates/rest_framework/vertical/select.html

@@ -3,8 +3,11 @@
         <label {% if style.hide_label %}class="sr-only"{% endif %}>{{ field.label }}</label>
     {% endif %}
     <select class="form-control" name="{{ field.name }}">
+        {% if field.allow_null %}
+            <option value="" {% if not field.value %}selected{% endif %}>--------</option>
+        {% endif %}
         {% for key, text in field.choices.items %}
-        <option value="{{ key }}" {% if key == field.value %}selected{% endif %}>{{ text }}</option>
+            <option value="{{ key }}" {% if key == field.value %}selected{% endif %}>{{ text }}</option>
         {% endfor %}
     </select>
     {% if field.errors %}