fix(combobox): dispatch change event on multiple combo changes

app/javascript/components/ComboBox.tsx

@@ -147,6 +147,7 @@ export function MultiComboBox(maybeProps: MultiComboBoxProps) {
     formValue,
     allowsCustomValue,
     valueSeparator,
+    className,
     ...props
   } = useMemo(() => s.create(maybeProps, MultiComboBoxProps), [maybeProps]);
 
@@ -174,7 +175,7 @@ export function MultiComboBox(maybeProps: MultiComboBoxProps) {
   const formResetRef = useOnFormReset(onReset);
 
   return (
-    <div className="fr-ds-combobox__multiple">
+    <div className={`fr-ds-combobox__multiple ${className}`}>
       {selectedItems.length > 0 ? (
         <TagGroup onRemove={onRemove} aria-label={props['aria-label']}>
           <TagList items={selectedItems} className="fr-tag-list">
@@ -203,7 +204,16 @@ export function MultiComboBox(maybeProps: MultiComboBoxProps) {
       </ComboBox>
       {name ? (
         <span ref={ref}>
-          {hiddenInputValues.map((value, i) => (
+          {hiddenInputValues.length == 0 ? (
+            <input
+              type="hidden"
+              value=""
+              name={name}
+              form={form}
+              ref={formResetRef}
+            />
+          ) : (
+            hiddenInputValues.map((value, i) => (
               <input
                 type="hidden"
                 value={value}
@@ -212,7 +222,8 @@ export function MultiComboBox(maybeProps: MultiComboBoxProps) {
                 ref={i == 0 ? formResetRef : undefined}
                 key={value}
               />
-          ))}
+            ))
+          )}
         </span>
       ) : null}
     </div>

app/javascript/components/react-aria/hooks.ts

@@ -23,6 +23,7 @@ export interface ComboBoxProps
 }
 
 const inputMap = new WeakMap<HTMLInputElement, string>();
+const inputCountMap = new WeakMap<HTMLSpanElement, number>();
 export function useDispatchChangeEvent() {
   const ref = useRef<HTMLSpanElement>(null);
 
@@ -30,12 +31,15 @@ export function useDispatchChangeEvent() {
     ref,
     dispatch: () => {
       requestAnimationFrame(() => {
-        const input = ref.current?.querySelector('input');
+        if (ref.current) {
-        if (input) {
+          const container = ref.current;
-          const value = input.value;
+          const inputs = Array.from(container.querySelectorAll('input'));
-          const prevValue = inputMap.get(input) || '';
+          const input = inputs.at(0);
-          if (value != prevValue) {
+          if (input && inputChanged(container, inputs)) {
-            inputMap.set(input, value);
+            inputCountMap.set(container, inputs.length);
+            for (const input of inputs) {
+              inputMap.set(input, input.value.trim());
+            }
             input.dispatchEvent(new Event('change', { bubbles: true }));
           }
         }
@@ -44,6 +48,23 @@ export function useDispatchChangeEvent() {
   };
 }
 
+// I am not proude of this code. We have to tack values and number of values to deal with multi select combobox.
+// I have a plan to remove this code. Soon.
+function inputChanged(container: HTMLSpanElement, inputs: HTMLInputElement[]) {
+  const prevCount = inputCountMap.get(container) ?? 0;
+  if (prevCount != inputs.length) {
+    return true;
+  }
+  for (const input of inputs) {
+    const value = input.value.trim();
+    const prevValue = inputMap.get(input);
+    if (prevValue == null || prevValue != value) {
+      return true;
+    }
+  }
+  return false;
+}
+
 export function useSingleList({
   defaultItems,
   defaultSelectedKey,
@@ -174,9 +195,13 @@ export function useMultiList({
   const filteredItems = useMemo(
     () =>
       inputValue.length == 0
-        ? items
+        ? items.filter((item) => !selectedKeys.has(item.value))
-        : matchSorter(items, inputValue, { keys: ['label'] }),
+        : matchSorter(
-    [items, inputValue]
+            items.filter((item) => !selectedKeys.has(item.value)),
+            inputValue,
+            { keys: ['label'] }
+          ),
+    [items, inputValue, selectedKeys]
   );
   const selectedItems = useMemo(() => {
     const selectedItems: Item[] = [];

app/models/champs/multiple_drop_down_list_champ.rb

@@ -73,7 +73,7 @@ class Champs::MultipleDropDownListChamp < Champ
   end
 
   def value=(value)
-    return super(nil) if value.nil?
+    return super(nil) if value.blank?
 
     values = if value.is_a?(Array)
       value

spec/models/champs/multiple_drop_down_list_champ_spec.rb

@@ -41,8 +41,6 @@ describe Champs::MultipleDropDownListChamp do
           expect(champ.value).to eq("[\"val1\"]")
           champ.value = 'val2'
           expect(champ.value).to eq("[\"val1\",\"val2\"]")
-          champ.value = ''
-          expect(champ.value).to eq("[\"val1\",\"val2\"]")
           champ.value = "[brackets] val4"
           expect(champ.value).to eq("[\"val1\",\"val2\",\"[brackets] val4\"]")
           champ.value = nil
@@ -51,6 +49,10 @@ describe Champs::MultipleDropDownListChamp do
           expect(champ.value).to eq("[\"val1\"]")
           champ.value = []
           expect(champ.value).to be_nil
+          champ.value = ["val1"]
+          expect(champ.value).to eq("[\"val1\"]")
+          champ.value = ''
+          expect(champ.value).to be_nil
         }
       end
     end