svelte-shim.ts

export default function (
  Component: typeof SvelteComponent,
  events?: { [svelteEvent: string]: string }
) {
  return class {
    $element: Element[];
    initialProps: { [key: string]: any };
    component: SvelteComponent;
    constructor($element) {
      'ngInject';
      this.$element = $element;
    }

    addInitialProps(extraProps) {
      this.initialProps = {
        ...this.initialProps,
        ...extraProps,
      };
    }

    $postLink() {
      this.component = new Component({
        target: this.$element[0],
        props: this.initialProps,
      });

      each(events || {}, (angularBinding, svelteEvent) => {
        this.component.$on(svelteEvent, ({ detail }) => {
          this[angularBinding](detail);
        });
      });
    }

    $onChanges(changes) {
      let changed = {};
      each(changes, ({ currentValue }, key) => {
        changed[key] = currentValue;
      });

      if (this.component) {
        this.component.$set(changed);
      } else {
        this.initialProps = {
          ...this.initialProps,
          ...changed,
        };
      }
    }

    $onDestroy() {
      if (this.component) {
        this.component.$destroy();
      }
    }
  };
}

If you're not using Typescript, you can find a plain ES6 version of this Gist at https://gist.github.com/rcline/af3a58cd5324dfcd5e7e22e7f3c64347