onChoicesLazyLoad isn't raised every time the search string changes if it happens rapidly

[jiyuan12354]

Description:

I am experiencing an issue with the onChoicesLazyLoad event in SurveyJS Dropdown. While the event handler is generally functioning as expected, I have noticed a problem when users rapidly and frequently update the search filter. In such cases, the onChoicesLazyLoad event does not always fire consistently, leading to search results that do not reflect the user's most recent input.

Code Example:

survey.onChoicesLazyLoad.add((_, options) => {
  const choicesLazyLoadByUrl = options.question?.choicesLazyLoadByUrl;
  if (choicesLazyLoadByUrl?.url) {
    const url = `${choicesLazyLoadByUrl?.url}?skip=${options.skip}&take=${options.take}&filter=${options.filter}`;
    http.get(url, {}).then(({ data }) => {
      let _options;
      if (choicesLazyLoadByUrl?.path) {
        _options = get(data, choicesLazyLoadByUrl?.path);
      } else {
        _options = data;
      }
      const opts = _options.map((option) => {
        return {
          value: get(option, choicesLazyLoadByUrl.valueName, option.value),
          text: get(option, choicesLazyLoadByUrl.titleName, option.text),
        };
      });
      options.setItems(opts, data.total);
    });
  }
});

Issue Details:

1. The choicesLazyLoadByUrl is a custom field and functions correctly.
2. When users rapidly type into the search filter, the onChoicesLazyLoad event is sometimes skipped.
   This leads to the displayed choices not matching the user's latest input.

Expected Behavior:

The onChoicesLazyLoad event should fire for every change in the search filter, ensuring that the dropdown choices are always based on the latest input string.

Actual Behavior:

When the search filter is updated rapidly, some onChoicesLazyLoad events are not triggered, resulting in outdated search results.

Could you please investigate this issue and provide a solution to ensure that the onChoicesLazyLoad event fires correctly even with rapid input changes?

Thank you for your assistance.

[jiyuan12354]

@OlgaLarina Hi OlgaLarina, I reviewed your code changes, and I believe it's not advisable to remove isRunningLoadQuestionChoices directly, as it cannot guarantee that the later request will receive the response last. Suppose you send out Requests A and B sequentially, but there's a possibility that you might receive Responses B and A in that order, which could lead to new issues.
Actually I made a patch in my local.

DropdownListModel.prototype.updateQuestionChoices = function (callbackAfterItemsLoaded) {
        var _this = this;
        if (this.isRunningLoadQuestionChoices)
            return;
        var theLoadingFilterString = this.filterString;
        var isUpdate = (this.itemsSettings.skip + 1) < this.itemsSettings.totalCount;
        if (!this.itemsSettings.skip || isUpdate) {
            this.isRunningLoadQuestionChoices = true;
            this.question.survey.loadQuestionChoices({
                question: this.question,
                filter: this.filterString,
                skip: this.itemsSettings.skip,
                take: this.itemsSettings.take,
                setItems: function (items, totalCount) {
                    _this.isRunningLoadQuestionChoices = false;
                    _this.setItems(items || [], totalCount || 0);
                    _this.popupRecalculatePosition(_this.itemsSettings.skip === _this.itemsSettings.take);
                    if (!!callbackAfterItemsLoaded) {
                        callbackAfterItemsLoaded();
                    }
                    if (theLoadingFilterString !== _this.filterString) {
                        _this.itemsSettings.skip = 0;
                        _this.itemsSettings.items = [];
                        _this.updateQuestionChoices(callbackAfterItemsLoaded);
                    }
                }
            });
            this.itemsSettings.skip += this.itemsSettings.take;
        }
    };

[jiyuan12354]

@OlgaLarina Hi OlgaLarina, I reviewed your code changes, and I believe it's not advisable to remove isRunningLoadQuestionChoices directly, as it cannot guarantee that the later request will receive the response last. Suppose you send out Requests A and B sequentially, but there's a possibility that you might receive Responses B and A in that order, which could lead to new issues. Actually I made a patch in my local.

DropdownListModel.prototype.updateQuestionChoices = function (callbackAfterItemsLoaded) {
        var _this = this;
        if (this.isRunningLoadQuestionChoices)
            return;
        var theLoadingFilterString = this.filterString;
        var isUpdate = (this.itemsSettings.skip + 1) < this.itemsSettings.totalCount;
        if (!this.itemsSettings.skip || isUpdate) {
            this.isRunningLoadQuestionChoices = true;
            this.question.survey.loadQuestionChoices({
                question: this.question,
                filter: this.filterString,
                skip: this.itemsSettings.skip,
                take: this.itemsSettings.take,
                setItems: function (items, totalCount) {
                    _this.isRunningLoadQuestionChoices = false;
                    _this.setItems(items || [], totalCount || 0);
                    _this.popupRecalculatePosition(_this.itemsSettings.skip === _this.itemsSettings.take);
                    if (!!callbackAfterItemsLoaded) {
                        callbackAfterItemsLoaded();
                    }
                    if (theLoadingFilterString !== _this.filterString) {
                        _this.itemsSettings.skip = 0;
                        _this.itemsSettings.items = [];
                        _this.updateQuestionChoices(callbackAfterItemsLoaded);
                    }
                }
            });
            this.itemsSettings.skip += this.itemsSettings.take;
        }
    };

No response here? I am sure there will have another issue by removing the isRunningLoadQuestionChoices flag.. your should fix it instead of removing it @OlgaLarina @RomanTsukanov @JaneSjs

[OlgaLarina]

Hello, @jiyuan12354
SurveyJS v1.11.4 introduces a dropdownSearchDelay setting that specifies how many milliseconds to wait before sending a search request to the server. You can find out more details here.
Therefore, isRunningLoadQuestionChoices is no longer needed.

Olga,
SurveyJS Team