Function sequence

packages/markmap-cli/src/util/dev-server.ts:25–33

(fn: () => MaybePromise<void>)

type MaybePromise<T> = T | Promise<T>;

function sequence(fn: () => MaybePromise<void>) {
  let promise: Promise<void> | undefined;
  return () => {
    promise ||= Promise.resolve(fn()).finally(() => {
      promise = undefined;
    });
    return promise;
  };
}

class BufferContentProvider implements IContentProvider {
  private deferredSet = new Set<IDeferred<void>>();