fix: Don't allow duplicated tag values in the Select (#19283)

* fix: Don't allow duplicated tag values in the Select

* Addresses comments and adds test

superset-frontend/src/components/Select/Select.test.tsx

@@ -314,6 +314,17 @@ test('searches for custom fields', async () => {
   expect(screen.getByText(NO_DATA)).toBeInTheDocument();
 });
 
+test('removes duplicated values', async () => {
+  render(<Select {...defaultProps} mode="multiple" allowNewOptions />);
+  await type('a,b,b,b,c,d,d');
+  const values = await findAllSelectValues();
+  expect(values.length).toBe(4);
+  expect(values[0]).toHaveTextContent('a');
+  expect(values[1]).toHaveTextContent('b');
+  expect(values[2]).toHaveTextContent('c');
+  expect(values[3]).toHaveTextContent('d');
+});
+
 test('renders a custom label', async () => {
   const options = [
     { label: 'John', value: 1, customLabel: <h1>John</h1> },

superset-frontend/src/components/Select/Select.tsx

@@ -385,31 +385,23 @@ const Select = (
 
   const hasCustomLabels = fullSelectOptions.some(opt => !!opt?.customLabel);
 
-  const handleOnSelect = (
-    selectedValue: string | number | AntdLabeledValue,
-  ) => {
+  const handleOnSelect = (selectedItem: string | number | AntdLabeledValue) => {
     if (isSingleMode) {
-      setSelectValue(selectedValue);
+      setSelectValue(selectedItem);
     } else {
-      const currentSelected = selectValue
-        ? Array.isArray(selectValue)
-          ? selectValue
-          : [selectValue]
-        : [];
-      if (
-        typeof selectedValue === 'number' ||
-        typeof selectedValue === 'string'
-      ) {
-        setSelectValue([
-          ...(currentSelected as (string | number)[]),
-          selectedValue as string | number,
-        ]);
-      } else {
-        setSelectValue([
-          ...(currentSelected as AntdLabeledValue[]),
-          selectedValue as AntdLabeledValue,
-        ]);
-      }
+      setSelectValue(previousState => {
+        const array = ensureIsArray(previousState);
+        const isObject = typeof selectedItem === 'object';
+        const value = isObject ? selectedItem.value : selectedItem;
+        // Tokenized values can contain duplicated values
+        if (!hasOption(value, array)) {
+          const result = [...array, selectedItem];
+          return isObject
+            ? (result as AntdLabeledValue[])
+            : (result as (string | number)[]);
+        }
+        return previousState;
+      });
     }
     setInputValue('');
   };