handlebars.js/lib/handlebars/decorators/inline.js

import { extend } from '../utils.js';

export default function (instance) {
  instance.registerDecorator(
    'inline',
    function (fn, props, container, options) {
      let ret = fn;
      if (!props.partials) {
        props.partials = {};
        ret = function (context, options) {
          // Create a new partials stack frame prior to exec.
          let original = container.partials;
          container.partials = extend({}, original, props.partials);
          let ret = fn(context, options);
          container.partials = original;
          return ret;
        };
      }

      props.partials[options.args[0]] = options.fn;

      return ret;
    }
  );
}