Method trackLoadPromise

packages/db/src/collection/sync.ts:445–475

* Tracks a load promise for isLoadingSubset state. * @internal This is for internal coordination (e.g., live-query glue code), not for general use.

(promise: Promise<void>)

   * @internal This is for internal coordination (e.g., live-query glue code), not for general use.
   */
  public trackLoadPromise(promise: Promise<void>): void {
    const loadingStarting = !this.isLoadingSubset
    this.pendingLoadSubsetPromises.add(promise)

    if (loadingStarting) {
      this._events.emit(`loadingSubset:change`, {
        type: `loadingSubset:change`,
        collection: this.collection,
        isLoadingSubset: true,
        previousIsLoadingSubset: false,
        loadingSubsetTransition: `start`,
      })
    }

    promise.finally(() => {
      const loadingEnding =
        this.pendingLoadSubsetPromises.size === 1 &&
        this.pendingLoadSubsetPromises.has(promise)
      this.pendingLoadSubsetPromises.delete(promise)

      if (loadingEnding) {
        this._events.emit(`loadingSubset:change`, {
          type: `loadingSubset:change`,
          collection: this.collection,
          isLoadingSubset: false,
          previousIsLoadingSubset: true,
          loadingSubsetTransition: `end`,
        })
      }
    })
  }

  /**
   * Requests the sync layer to load more data.