Method startUsed_

src/core/context/values.js:363–418

* Start the used value tracker if it hasn't started yet. * * @param {IContextProp } prop * @return {IContextPropUsed } * @private * @template T, DEP

(prop)

   * @template T, DEP
   */
  startUsed_(prop) {
    const {deps, key} = prop;
    const usedByKey = this.usedByKey_ || (this.usedByKey_ = new Map());
    let used = usedByKey.get(key);
    if (!used) {
      used = {
        prop,
        subscribers: [],
        value: undefined,
        pending: Pending_Enum.NOT_PENDING,
        counter: 0,
        depValues: deps.length > 0 ? deps.map(EMPTY_FUNC) : EMPTY_ARRAY,
        parentValue: undefined,
        parentContextNode: null,
        // Schedule the value recalculation, optionally with the parent
        // refresh.
        /** @type {function(boolean):void} */
        ping: (refreshParent) => {
          if (this.isConnected_()) {
            const pending = refreshParent
              ? Pending_Enum.PENDING_REFRESH_PARENT
              : Pending_Enum.PENDING;
            used.pending = Math.max(used.pending, pending);
            this.checkUpdates_();
          }
        },
        // Schedule the value recalculation due to the dependency change.
        pingDep:
          deps.length > 0
            ? deps.map((dep, index) => {
                /** @param {DEP} value*/
                return (value) => {
                  used.depValues[index] = value;
                  used.ping();
                };
              })
            : EMPTY_ARRAY,
        // Schedule the value recalculation due to the parent value change.
        pingParent: isRecursive(prop)
          ? /** @param {T} parentValue */
            (parentValue) => {
              used.parentValue = parentValue;
              used.ping();
            }
          : null,
      };
      usedByKey.set(key, used);

      // Subscribe to all deps.
      deps.forEach((dep, index) => this.subscribe(dep, used.pingDep[index]));

      // Schedule the first refresh.
      used.ping(false);
    }
    return used;
  }

  /**