make sure at least one Plugin is selected

Summary:
Selecting no plugins during Flipper file / link export would continue the export process but yield meaningless export files. Added validation something is selected

See https://fb.workplace.com/groups/flippersupport/permalink/1805444636602853/

Reviewed By: LukeDefeo

Differential Revision: D55467979

fbshipit-source-id: 331c70fc80817bc193bace44f16a0d29259a250b

desktop/flipper-plugin/src/ui/Dialog.tsx

@@ -242,6 +242,7 @@ export const Dialog = {
   select<T>({
     defaultValue,
     renderer,
+    onValidate,
     ...rest
   }: {
     defaultValue: T;
@@ -250,10 +251,12 @@ export const Dialog = {
       onChange: (newValue: T) => void,
       onCancel: () => void,
     ) => React.ReactElement;
+    onValidate?: (value: T) => string;
   } & BaseDialogOptions): DialogResult<false | T> {
     const handle = Dialog.show<T>({
       ...rest,
       defaultValue,
+      onValidate,
       children: (currentValue, setValue): React.ReactElement =>
         renderer(currentValue, setValue, () => handle.close()),
     });

desktop/flipper-ui/src/chrome/ExportDataPluginSheet.tsx

@@ -37,7 +37,7 @@ class ExportDataPluginSheet extends Component<Props, {}> {
       <Container>
         <ListView
           type="multiple"
-          title="Select the plugins for which you want to export the data"
+          title="Select the plugins of the currently active device / application for which you want to export the data"
           leftPadding={8}
           onChange={(selectedArray) => {
             this.props.setSelectedPlugins(selectedArray);

desktop/flipper-ui/src/utils/exportData.tsx

@@ -772,6 +772,8 @@ async function selectPlugins() {
   return await Dialog.select<string[]>({
     title: 'Select plugins to export',
     defaultValue: [],
+    onValidate: (plugins) =>
+      plugins.length === 0 ? 'Please select at least one plugin.' : '',
     renderer: (value, onChange, onCancel) => (
       <ExportDataPluginSheet
         onHide={onCancel}