From f6912b5a48dcd1ab7650e55f392428b838d7d7b6 Mon Sep 17 00:00:00 2001
From: Niclas Liimatainen <niclas.liimatainen@digia.com>
Date: Fri, 5 Jun 2020 12:54:06 +0300
Subject: [PATCH] Add support for controlling selected option(s)

---
 .../components/dropdown/Dropdown.stories.tsx  | 47 ++++++++++++++++++-
 .../src/components/dropdown/Dropdown.tsx      |  9 ++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/packages/react/src/components/dropdown/Dropdown.stories.tsx b/packages/react/src/components/dropdown/Dropdown.stories.tsx
index 6d30d3e0dd..381ef6d9fa 100644
--- a/packages/react/src/components/dropdown/Dropdown.stories.tsx
+++ b/packages/react/src/components/dropdown/Dropdown.stories.tsx
@@ -1,7 +1,8 @@
-import React from 'react';
+import React, { useState } from 'react';
 import { boolean, number, text, withKnobs } from '@storybook/addon-knobs';
 
 import Dropdown from './Dropdown';
+import Button from '../button/Button';
 
 const options = [
   { label: 'Plutonium' },
@@ -76,6 +77,50 @@ export const Multiselect = () => (
   />
 );
 
+export const Controlled = () => {
+  const [selectedItem, setSelectedItem] = useState(null);
+  const [multiselectSelectedItem, setMultiselectSelectedItem] = useState(null);
+
+  const handleSelectedItemChange = (item) => setSelectedItem(item);
+  const handleMultiselectSelectedItemChange = (item) => setMultiselectSelectedItem(item);
+
+  return (
+    <>
+      <Button onClick={() => setSelectedItem(null)}>Reset</Button>
+      {['Dropdown 1', 'Dropdown 2'].map((label) => (
+        <Dropdown
+          key={label}
+          options={options}
+          placeholder="Placeholder"
+          label={label}
+          onChange={handleSelectedItemChange}
+          selectedOption={selectedItem}
+          style={{ marginTop: 'var(--spacing-s)' }}
+        />
+      ))}
+      <Button onClick={() => setMultiselectSelectedItem(null)} style={{ marginTop: 'var(--spacing-xl)' }}>
+        Reset multiselect
+      </Button>
+      {['Multiselect 1', 'Multiselect 2'].map((label) => (
+        <Dropdown
+          key={label}
+          options={options}
+          placeholder="Placeholder"
+          label={label}
+          multiselect
+          onChange={handleMultiselectSelectedItemChange}
+          selectedOption={multiselectSelectedItem}
+          style={{ marginTop: 'var(--spacing-s)' }}
+        />
+      ))}
+    </>
+  );
+};
+
+Controlled.story = {
+  name: 'With controlled state',
+};
+
 Multiselect.story = {
   name: 'With multiselect',
 };
diff --git a/packages/react/src/components/dropdown/Dropdown.tsx b/packages/react/src/components/dropdown/Dropdown.tsx
index 797a604542..8cdf62024f 100644
--- a/packages/react/src/components/dropdown/Dropdown.tsx
+++ b/packages/react/src/components/dropdown/Dropdown.tsx
@@ -113,6 +113,10 @@ export type DropdownProps = {
    * If `true`, the label is displayed as required
    */
   required?: boolean;
+  /**
+   * The option(s) that should be selected
+   */
+  selectedOption?: OptionType | OptionType[];
   /**
    * Override or extend the root styles applied to the component
    */
@@ -171,6 +175,7 @@ const Dropdown: FC<DropdownProps> = ({
   options = [],
   placeholder = '',
   required,
+  selectedOption,
   style,
   toggleButtonId,
   visibleOptions = 5,
@@ -188,6 +193,7 @@ const Dropdown: FC<DropdownProps> = ({
   // init multi-select
   const { getDropdownProps, addSelectedItem, removeSelectedItem, selectedItems } = useMultipleSelection<OptionType>({
     initialSelectedItems: defaultValues,
+    ...(multiselect && selectedOption !== undefined && { selectedItems: (selectedOption as OptionType[]) ?? [] }),
     onSelectedItemsChange: ({ selectedItems: _selectedItems }) => multiselect && onChange(_selectedItems),
   });
 
@@ -233,6 +239,9 @@ const Dropdown: FC<DropdownProps> = ({
     onSelectedItemChange: ({ selectedItem }) => !multiselect && onChange(selectedItem),
     // selected items are handled by stateReducer when multiselect is enabled
     ...(multiselect && { selectedItem: null }),
+    // a value for selectedOption indicates that the dropdown should be controlled
+    // don't set selectedItem if it's not, so that downshift can control the selected item(s)
+    ...(!multiselect && selectedOption !== undefined && { selectedItem: selectedOption }),
     stateReducer,
     toggleButtonId,
   };