blocks: add support for post conditions (#71778)

wcs/blocks.py

@@ -544,9 +544,9 @@ class BlockWidget(WidgetList):
             if self.required and self.value is None:
                 self.set_error(_(self.REQUIRED_ERROR))
             for widget in self.widgets:
-                # do not mark individual rows as required
-                if widget.error == self.REQUIRED_ERROR:
-                    widget.clear_error()
+                # mark required rows with a special attribute, to avoid doubling the
+                # error messages in the template.
+                widget.is_required_error = bool(widget.error == self.REQUIRED_ERROR)
         return self.value
 
     def add_media(self):

wcs/qommon/templates/qommon/forms/widgets/block_sub.html

@@ -6,7 +6,7 @@
 {% endblock %}
 
 {% block widget-content %}
-  {% if not widget.readonly and widget.error %}<div class="error"><p>{{ widget.error }}</p></div>{% endif %}
+  {% if not widget.readonly and widget.error and not widget.is_required_error %}<div class="error"><p>{{ widget.error }}</p></div>{% endif %}
   {% for subwidget in widget.get_widgets %}
     {% if widget.readonly and not subwidget.field.include_in_validation_page %}<div style="display: none">{% endif %}
     {{ subwidget.render|safe }}