Function then

packages/react-cache/src/__tests__/ReactCacheOld-test.internal.js:52–84

(resolve, reject)

        let value = null;
        return {
          then(resolve, reject) {
            switch (status) {
              case 'pending': {
                if (listeners === null) {
                  listeners = [{resolve, reject}];
                  setTimeout(() => {
                    if (textResourceShouldFail) {
                      Scheduler.log(`Promise rejected [${text}]`);
                      status = 'rejected';
                      value = new Error('Failed to load: ' + text);
                      listeners.forEach(listener => listener.reject(value));
                    } else {
                      Scheduler.log(`Promise resolved [${text}]`);
                      status = 'resolved';
                      value = text;
                      listeners.forEach(listener => listener.resolve(value));
                    }
                  }, ms);
                } else {
                  listeners.push({resolve, reject});
                }
                break;
              }
              case 'resolved': {
                resolve(value);
                break;
              }
              case 'rejected': {
                reject(value);
                break;
              }
            }
          },
        };
      },
      ([text, ms]) => text,