The special rsf:id payload-component is reserved, and is designed to help out with the very common situation where otherwise one might need to create a UIBranchContainer containing a single component.

The situation comes up quite often, where there is a piece of markup surrounding a component which is optional, which you want to suppress in addition to the component when the component is not there. For example, imagine the following bit of template:

<span rsf:id="label-branch:">This is the description for <span rsf:id="component">My Component</span></span>

The component component (probably a UIOutput} is optional, and the producer may choose to leave it out. But without the branch here, what might be left behind is the text "This is the description for" which is clearly nonsensical. So, without payload-component, the conditional one would test in the producer would suppress the entire label-branch: as well as the component inside.

if (showcomponent) {
  UIBranchContainer mybranch = UIBranchContainer.make(tofill, "label-branch:");
  UIOutput.make(mybranch, "component", "My Component");
  }

Considering that the ids for all branch containers are resolved within a global scope, this would be an increasing risk, as well as being very annoying. The special payload-component id lets us deal with this situation using only leaf components and only the original component in the producer.

In the template, we apply the "real" id to the entire tag in the template that we want suppressed if the component is missing - and to the tag inside it which will actually peer with the component when it is present, we give the special id payload-component - like this:

<span rsf:id="component">This is the description for <span rsf:id="payload-component">My Component</span></span>

This structure is "invisible" in the producer - we simply deal with the "real" component as follows:

if (showcomponent) {
  UIOutput.make(tofill, "component, "My Component");
  }

As of RSF 0.7, payload-component works with payloads which are both normal leaves and repetitive leaves.