make WidgetWithScript explicitly fail in the absence of an ID attribute

wagtail/utils/widgets.py

@@ -10,12 +10,14 @@ class WidgetWithScript(Widget):
         return super(WidgetWithScript, self).render(name, value, attrs)
 
     def render(self, name, value, attrs=None):
-        widget_html = self.render_html(name, value, attrs)
+        # no point trying to come up with sensible semantics for when 'id' is missing from attrs,
+        # so let's make sure it fails early in the process
+        try:
+            id_ = attrs['id']
+        except KeyError, TypeError:
+            raise TypeError("WidgetWithScript cannot be rendered without an 'id' attribute")
 
-        final_attrs = self.build_attrs(attrs, name=name)
-        id_ = final_attrs.get('id', None)
-        if id_ is None:
-            return widget_html
+        widget_html = self.render_html(name, value, attrs)
 
         js = self.render_js_init(id_, name, value)
         out = '{0}<script>{1}</script>'.format(widget_html, js)

wagtail/wagtailadmin/widgets.py

@@ -6,6 +6,7 @@ from django.core.urlresolvers import reverse
 from django.forms import widgets
 from django.contrib.contenttypes.models import ContentType
 from django.utils.translation import ugettext_lazy as _
+from django.template.loader import render_to_string
 
 from wagtail.utils.widgets import WidgetWithScript
 from wagtail.wagtailcore.models import Page
@@ -61,6 +62,14 @@ class AdminPageChooser(AdminChooser):
         super(AdminPageChooser, self).__init__(**kwargs)
         self.target_content_type = content_type or ContentType.objects.get_for_model(Page)
 
+    def render_html(self, name, value, attrs):
+        original_field_html = super(AdminPageChooser, self).render_html(name, value, attrs)
+
+        return render_to_string("wagtailadmin/widgets/page_chooser.html", {
+            'original_field_html': original_field_html,
+            'widget': self,
+        })
+
     def render_js_init(self, id_, name, value):
         page = Page.objects.get(pk=value) if value else None
         parent = page.get_parent() if page else None