Ability to filter suggestions before display

[cdtinney]

Do you want to request a feature or report a bug?

Feature.

What is the current behavior?

• Suggestions are retrieved via querying dataset sources
• Suggestions are cached so that subsequent identical queries do not query the dataset source
• Suggestions are not filtered before displaying

What is the expected behavior?

• Suggestions can be filtered both after a query or cache hit, before they are displayed

Use Case

I am using the autocomplete input to allow the user to add "tags" to a list. If the user adds a tag, it needs to be hidden from the dropdown subsequently (i.e. the tag can only be added once).

Workarounds I've Tried

• Using a template for suggestion that returns an empty element. This doesn't work when there are no suggestions as the empty template doesn't get rendered.
• Filtering results after the dataset source is queried. This works for all cases except cache hits.

Alternatives

One alternative would be to allow developers to override caching behaviour.

[Haroenv]

The second argument to the hits function accepts any search parameter, and thus allows you to filter. All filtering options are available here: https://www.algolia.com/doc/api-reference/search-api-parameters/

[cdtinney]

@Haroenv I'm not using an Algolia source. Would that be called even if suggestions were cached, though?

[Haroenv]

Autocomplete doesn't have a cache, can you give the code you're using?

[cdtinney]

Using jQuery JS for v0.31.0.

This looks like caching to me: https://github.com/algolia/autocomplete.js/blob/v0.31.0/dist/autocomplete.jquery.js#L2537

[Haroenv]

I didn't know that, I've only worked on other parts of the code base. Do you have a suggestion on how to fix it, maybe allow disabling of the cache?

The best way would be that you allow filtering (maybe with a callback argument) to your own source, that way you can control filtering without a change in cache etc.

[cdtinney]

I think filtering is the best approach as disabling cache requires more work for the developers (disable cache + handle filtering of results).

A new option called filter could be added to dataset objects. This should be a function.

It could be implemented inside the handleSuggestions function inside update:

function handleSuggestions(suggestions) {  
  // if the update has been canceled or if the query has changed
  // do not render the suggestions as they've become outdated
  if (this.canceled || query !== this.query) {
    return;
  }

  // Apply filters
  var filteredSuggestions = this._applyFilters(suggestions);

  // concat all the other arguments that could have been passed
  // to the render function, and forward them to _render
  var extraArgs = [].slice.call(arguments, 1);
  this.cacheSuggestions(query, filteredSuggestions, extraArgs);
  this._render.apply(this, [query, filteredSuggestions].concat(extraArgs));
}

Thoughts?

[Haroenv]

Is there a reason you prefer this in the library over putting it in userspace (like the Algolia one does)

[cdtinney]

I'm not sure how to implement it in userspace to bypass the caching since the source function won't be called at all. I could add query parameters to do the filtering server side, yes, but that requires source to be called.

Suggestions are welcome.

[cdtinney]

I have this implemented locally. Would you be open to a PR (with tests, docs, etc.)?

[Haroenv]

Would be interesting to see what you came up with yes 😊

I've taken a deeper look and noticed that the cache in autocomplete.js is only for a single previous query. In the case of filtering frontend, it should be fairly safe to simply disabling the cache, but I think it will make more sense when I see what your implementation is

[cdtinney]

It turns out that filtering is not sufficient. There is an edge case that it doesn't handle:

• Enter query X
• Source returns results A, B, C
• A is deleted from the server by aother user
• Enter query X again
• Source returns same results

Disabling caching is a better approach. It still leaves caching possible in userspace. I will work on a MR.

[Haroenv]

Thanks, that's what I thought would be more appropriate too! a PR would be appreciated 🚀

[cdtinney]

Closing. There is another solution that doesn't require lib changes: passing the filter function to the dataset on initialization.