[Autocomplete] Fix keyboard usage in Single mode (#3930)

Author: dvoituron

src/Core/Components/List/FluentAutocomplete.razor

@@ -216,7 +216,14 @@
 
                     if (Multiple == false)
                     {
-                        <FluentLabel tabindex="0" aria-label="@GetOptionText(item)" role="checkbox" aria-checked="true">@text</FluentLabel>
+                        <FluentLabel Id="@($"{Id}-single")"
+                                     tabindex="0"
+                                     aria-label="@GetOptionText(item)"
+                                     role="checkbox"
+                                     aria-checked="true"
+                                     @onkeydown="@(e => e.Code == "Delete" || e.Code == "Backspace" ? RemoveSelectedItemAsync(item) : Task.CompletedTask)">
+                            @text
+                        </FluentLabel>
                     }
                     else if (ReadOnly || Disabled)
                     {

src/Core/Components/List/FluentAutocomplete.razor.cs

@@ -327,7 +327,7 @@ public async Task InvokeOptionsSearchAsync()
         Items = args.Items?.Take(MaximumOptionsSearch);
 
         SelectableItem = Items != null
-            ? Items.FirstOrDefault()
+            ? Items.FirstOrDefault(i => OptionDisabled is null ? true : OptionDisabled.Invoke(i) == false)
             : default;
 
         if (VirtualizationContainer != null)
@@ -558,6 +558,13 @@ protected override async Task OnSelectedItemChangedHandlerAsync(TOption? item)
         await RaiseValueTextChangedAsync(ValueText);
 
         await base.OnSelectedItemChangedHandlerAsync(item);
+
+        // In Single mode, set the focus on the input field
+        if (!Multiple && Module != null)
+        {
+            await Module.InvokeVoidAsync("focusOn", $"{Id}-single");
+        }
+
         await DisplayLastSelectedItemAsync();
 
         if (MustBeClosed())

src/Core/Components/List/ListComponentBase.razor.cs

@@ -568,6 +568,14 @@ protected virtual async Task OnSelectedItemChangedHandlerAsync(TOption? item)
                 InternalValue = GetOptionValue(item);
                 await RaiseChangedEventsAsync();
             }
+
+            // For Autocomplete, allow to unselect the item if it is already selected
+            else if (this is FluentAutocomplete<TOption>)
+            {
+                SelectedOption = default;
+                InternalValue = GetOptionValue(default);
+                await RaiseChangedEventsAsync();
+            }
         }
     }
 
@@ -632,6 +640,12 @@ protected virtual bool RemoveSelectedItem(TOption? item)
             return false;
         }
 
+        if (this is FluentAutocomplete<TOption> && SelectedOption is not null)
+        {
+            SelectedOption = default;
+            InternalValue = GetOptionValue(default);
+        }
+
         return _selectedOptions.Remove(item);
     }