Deprecation: Widget body (w‐body) - marko-js/marko GitHub Wiki

The w-body attribute is deprecated in favor of the <${dynamicTagname}/> syntax.

getInitialBody(input, out) {
   return input.renderBody || input.label
}

<button>
  <span w-body/>
</button>

…becomes:

<button>
  <if(input.renderBody)>
    <${input.renderBody}/>
  </if>
  <else>
    ${input.label}
  </else>
</button>

To automatically fix deprecated marko syntax, try the marko migrate command from the CLI.