replace FieldBlock rendering with a template-based version that tries to replicate our standard form field markup

wagtail/wagtailadmin/blocks.py

@@ -218,10 +218,10 @@ class FieldBlock(Block):
 
         widget_html = widget.render(prefix, value, {'id': prefix})
 
-        if error:
-            error_html = str(ErrorList(error.error_list))
-        else:
-            error_html = ''
+        #if error:
+        #    error_html = str(ErrorList(error.error_list))
+        #else:
+        #    error_html = ''
 
         if self.label:
             label_html = format_html(
@@ -231,7 +231,12 @@ class FieldBlock(Block):
         else:
             label_html = ''
 
-        return mark_safe(error_html + label_html + widget_html)
+        return render_to_string('wagtailadmin/block_forms/field.html', {
+            'widget': widget_html,
+            'label_tag': label_html,
+            'field': self.field,
+            'errors': error.error_list if error else [],  # TODO: should this be ErrorList(error.error_list)?
+        })
 
     def value_from_datadict(self, data, files, prefix):
         return self.field.widget.value_from_datadict(data, files, prefix)

wagtail/wagtailadmin/templates/wagtailadmin/block_forms/field.html

@@ -0,0 +1,23 @@
+{% load wagtailadmin_tags %}
+<div class="field {{ field|fieldtype }}">
+    {{ field.label_tag }}
+    <div class="field-content">
+        <div class="input">
+            {{ widget }}
+
+            {# This span only used on rare occasions by certain types of input #}
+            <span></span>
+        </div>
+        {% if field.help_text %}
+            <p class="help">{{ field.help_text }}</p>
+        {% endif %}
+
+        {% if errors %}
+            <p class="error-message">
+                {% for error in errors %}
+                    <span>{{ error|escape }}</span>
+                {% endfor %}
+            </p>
+        {% endif %}
+    </div>
+</div>