@comyata/run/ValueSubscriberPromise.js

Simplify data workflows and management with data templates, for browser and server.

/**
 * @internal
 */
export class ValueSubscriberPromise extends Promise {
  #dependents = new Set();
  #subscribers;
  #result = undefined;
  constructor(subscribers, dataNode) {
    super(resolve => {
      // throwing here may lead to uncaught errors in react but not nodejs somehow,
      // in react it is only used to know when to show progress loaders in e.g. JSONView, but not awaited
      // as anything which tries to listen, will receive rejects below and the actual exception is handled at another position,
      // it should be best and safe to just set to undefined on errors
      subscribers.push((nodeResult, err) => {
        this.#result = err ? {
          error: err
        } : {
          value: nodeResult
        };
        resolve(err ? undefined : nodeResult);
      });
    });
    this.#subscribers = subscribers;
    this.dataNode = () => dataNode;
  }
  addDependent(n) {
    this.#dependents.add(n);
  }
  hasDependent(n) {
    return this.#dependents.has(n);
  }
  getDependents() {
    return Array.from(this.#dependents);
  }
  then(onfulfilled, onrejected) {
    if (this.#result) {
      return (this.#result.error ? Promise.reject(this.#result.error) : Promise.resolve(this.#result.value)).then(onfulfilled, onrejected);
    }
    return new Promise((resolve, reject) => {
      this.#subscribers.push((result, err) => {
        if (err) {
          reject(err);
          return;
        }
        resolve(result);
      });
    }).then(onfulfilled, onrejected);
  }
  catch(onrejected) {
    if (this.#result) {
      return (this.#result.error ? Promise.reject(this.#result.error) : Promise.resolve(this.#result.value)).catch(onrejected);
    }
    return new Promise((resolve, reject) => {
      this.#subscribers.push((result, err) => {
        if (err) {
          reject(err);
          return;
        }
        resolve(result);
      });
    }).catch(onrejected);
  }
}