Example code that breaks:
<t:Radio t:id="radio1" t:value="value1"/><t:Label for="radio1"/>
No object of type org.apache.tapestry.RadioContainer is available from the Environment.
The reason is that the Label validation rendering calls Radio.getElementName() after the RadioGroup has been popped from the environment.
A simple fix is to cache the element name:
private String _elementName;
public String getElementName()
void beginRender(MarkupWriter writer)