React: inline conditionally pass prop to component

You were close with your idea. It turns out that passing undefined for a prop is the same as not including it at all, which will still trigger the default prop value. So you could do something like this:

var parent = React.createClass({
  propTypes: {
    editable: React.PropTypes.bool.isRequired,
    editableOpts: React.PropTypes.shape({...})
  },
  render: function() {
    return <Child 
      editable={this.props.editable ?
                  this.props.editableOpts : 
                  undefined}
    />;
  }
});