[Autocomplete] Option highlighted event

[aslupik]

• [x ] I have searched the issues of this repository and believe that this is not a duplicate.

Summary 💡

<Autocomplete
   onOptionHighlighted={(option: T, reason: 'keyboardNavigation' | 'mouseOver' | 'automatic') => { ... }}
   ...
/>

This event would trigger when an option is highlighted (such that pressing Enter would then select that option). For instance, it would trigger upon using the arrow keys to cycle through the options and report which option is currently highlighted.

Motivation 🔦

Give context to the user on the highlighted option to allow him to make a better choice. Right now, we only know which option is selected after the user makes a choice; this would allow providing feedback proactively rather than reactively.

[oliviertassinari]

Give context to the user on the highlighted option to allow him to make a better choice.

@aslupik How do you plan to implement this extra context? (assuming you have this callback available).

[aslupik]

Give context to the user on the highlighted option to allow him to make a better choice.

@aslupik How do you plan to implement this extra context? (assuming you have this callback available).

I'm using Redux, so the callback would trigger an action allowing the rest of the application to know which option is currently highlighted. Then, a separate component on the page can subscribe to that and display information related to the highlighted option. This component updates dynamically as the user cycles through the options in the dropdown.

[oliviertassinari]

@aslupik Ok sounds fair. What do you think of this API to anticipate for a future case when somebody will need to control the highlighted option (at the cost of harming performance, I imagine)

diff --git a/packages/material-ui-lab/src/useAutocomplete/useAutocomplete.d.ts b/packages/material-ui-lab/src/useAutocomplete/useAutocomplete.d.ts
index 910be8d93..0dd380265 100644
--- a/packages/material-ui-lab/src/useAutocomplete/useAutocomplete.d.ts
+++ b/packages/material-ui-lab/src/useAutocomplete/useAutocomplete.d.ts
@@ -134,6 +134,18 @@ export interface UseAutocompleteCommonProps<T> {
    * @param {string} reason Can be: `"toggleInput"`, `"escape"`, `"select-option"`, `"blur"`.
    */
   onClose?: (event: React.ChangeEvent<{}>, reason: AutocompleteCloseReason) => void;
+  /**
+   * Callback  fired when the highlighted option changes.
+   *
+   * @param {object} event The event source of the callback.
+   * @param {T} option
+   * @param {string} reason Can be: `"keyboard"`, `"auto"`, `"mouseOver"`.
+   */
+  onHighlightChange?: (
+    event?: React.ChangeEvent<{}>,
+    option: T,
+    reason: AutocompleteHighlightChangeReason
+  );
   /**
    * Callback fired when the input value changes.
    *
@@ -178,6 +190,12 @@ export type AutocompleteChangeReason =
   | 'remove-option'
   | 'clear'
   | 'blur';
+
+export type AutocompleteHighlightChangeReason =
+  | 'keyboard'
+  | 'mouseOver'
+  | 'auto';
+
 export interface AutocompleteChangeDetails<T = string> {
   option: T;
 }

[aslupik]

@oliviertassinari That looks good to me!

[marcosvega91]

I Will create a PR with this feature soon :)

[abbasyadollahi]

@oliviertassinari @marcosvega91
There seems to be an issue with this new feature when used alongside the filterSelectedOptions prop.

When navigating over the listbox options, the value argument passed to the onHighlightChange function doesn't take into consideration the options that have been filtered out by the input. As a result, value corresponds to the same index option as if there was no filter.

I made a small sandbox to show what I mean. The first option (Jaws) is correct, but starting from the second option (Avengers), the values are shifted by one position.

[marcosvega91]

Hi @theGirrafish I will correct the issue :)