[select] fix: mark items arrays as readonly where appropriate

packages/docs-app/src/examples/select-examples/multiSelectExample.tsx

@@ -209,7 +209,7 @@ export class MultiSelectExample extends React.PureComponent<IExampleProps, IMult
         this.selectFilms([film]);
     }
 
-    private selectFilms(filmsToSelect: IFilm[]) {
+    private selectFilms(filmsToSelect: readonly IFilm[]) {
         const { createdItems, films, items } = this.state;
 
         let nextCreatedItems = createdItems.slice();
@@ -259,7 +259,7 @@ export class MultiSelectExample extends React.PureComponent<IExampleProps, IMult
         }
     };
 
-    private handleFilmsPaste = (films: IFilm[]) => {
+    private handleFilmsPaste = (films: readonly IFilm[]) => {
         // On paste, don't bother with deselecting already selected values, just
         // add the new ones.
         this.selectFilms(films);

packages/docs-theme/src/components/navigator.tsx

@@ -85,7 +85,7 @@ export class Navigator extends React.PureComponent<INavigatorProps> {
     }
 
     private filterMatches: ItemListPredicate<INavigationSection> = (query, items) =>
-        filter(items, query, {
+        filter([...items], query, {
             key: "route",
             maxInners: items.length / 5,
             maxResults: 10,

packages/select/src/common/itemListRenderer.ts

@@ -37,13 +37,13 @@ export interface IItemListRendererProps<T> {
      * map each item in this array through `renderItem`, with support for
      * optional `noResults` and `initialContent` states.
      */
-    filteredItems: T[];
+    filteredItems: readonly T[];
 
     /**
      * Array of all items in the list.
      * See `filteredItems` for a filtered array based on `query` and predicate props.
      */
-    items: T[];
+    items: readonly T[];
 
     /**
      * The current query string.

packages/select/src/common/listItemsProps.ts

@@ -44,7 +44,7 @@ export interface IListItemsProps<T> extends Props {
     activeItem?: T | ICreateNewItem | null;
 
     /** Array of items in the list. */
-    items: T[];
+    items: readonly T[];
 
     /**
      * Specifies how to test if two items are equal. By default, simple strict
@@ -155,7 +155,7 @@ export interface IListItemsProps<T> extends Props {
     /**
      * Callback invoked when multiple items are selected at once via pasting.
      */
-    onItemsPaste?: (items: T[]) => void;
+    onItemsPaste?: (items: readonly T[]) => void;
 
     /**
      * Callback invoked when the query string changes.

packages/select/src/common/predicate.ts

@@ -18,7 +18,7 @@
  * A custom predicate for returning an entirely new `items` array based on the provided query.
  * See usage sites in `IListItemsProps`.
  */
-export type ItemListPredicate<T> = (query: string, items: T[]) => T[];
+export type ItemListPredicate<T> = (query: string, items: readonly T[]) => readonly T[];
 
 /**
  * A custom predicate for filtering items based on the provided query.

packages/select/src/components/query-list/queryList.tsx

@@ -134,7 +134,7 @@ export interface IQueryListState<T> {
     createNewItem: T | undefined;
 
     /** The original `items` array filtered by `itemListPredicate` or `itemPredicate`. */
-    filteredItems: T[];
+    filteredItems: readonly T[];
 
     /** The current query string. */
     query: string;
@@ -645,7 +645,7 @@ function isItemDisabled<T>(item: T | null, index: number, itemDisabled?: IListIt
  * @param startIndex which index to begin moving from
  */
 export function getFirstEnabledItem<T>(
-    items: T[],
+    items: readonly T[],
     itemDisabled?: keyof T | ((item: T, index: number) => boolean),
     direction = 1,
     startIndex = items.length - 1,

packages/select/src/components/select/multiSelect.tsx

@@ -83,7 +83,7 @@ export interface IMultiSelectProps<T> extends IListItemsProps<T> {
     popoverProps?: Partial<IPopoverProps> & object;
 
     /** Controlled selected values. */
-    selectedItems?: T[];
+    selectedItems?: readonly T[];
 
     /** Props to spread to `TagInput`. Use `query` and `onQueryChange` to control the input. */
     // eslint-disable-next-line @typescript-eslint/ban-types

packages/select/test/queryListTests.tsx

@@ -85,7 +85,9 @@ describe("<QueryList>", () => {
         });
 
         it("itemListPredicate filters entire list by query", () => {
-            const predicate = sinon.spy((query: string, films: IFilm[]) => films.filter(f => f.year === +query));
+            const predicate = sinon.spy((query: string, films: readonly IFilm[]) =>
+                films.filter(f => f.year === +query),
+            );
             shallow(<FilmQueryList {...testProps} itemListPredicate={predicate} query="1994" />);
 
             assert.equal(predicate.callCount, 1, "called once for entire list");