feat(prompts): support readonly options in multiselect

.changeset/quiet-moons-matter.md

@@ -0,0 +1,6 @@
+---
+"@clack/prompts": minor
+"@clack/core": patch
+---
+
+Allow `multiselect` to accept readonly option arrays, e.g. options declared with `as const`. The `Value` type parameter is now inferred as a literal union (`'a' | 'b'`) from such arrays, and `initialValues` also accepts readonly arrays.

packages/core/src/prompts/multi-select.ts

@@ -8,13 +8,13 @@ interface OptionLike {
 
 export interface MultiSelectOptions<T extends OptionLike>
 	extends PromptOptions<T['value'][], MultiSelectPrompt<T>> {
-	options: T[];
-	initialValues?: T['value'][];
+	options: readonly T[];
+	initialValues?: readonly T['value'][];
 	required?: boolean;
 	cursorAt?: T['value'];
 }
 export default class MultiSelectPrompt<T extends OptionLike> extends Prompt<T['value'][]> {
-	options: T[];
+	options: readonly T[];
 	cursor = 0;
 
 	private get _value(): T['value'] {

packages/core/src/utils/cursor.ts

@@ -1,7 +1,7 @@
 export function findCursor<T extends { disabled?: boolean }>(
 	cursor: number,
 	delta: number,
-	options: T[]
+	options: readonly T[]
 ) {
 	const hasEnabledOptions = options.some((opt) => !opt.disabled);
 	if (!hasEnabledOptions) {

packages/prompts/src/limit-options.ts

@@ -10,7 +10,7 @@ export interface LimitOptionsParams<TOption> extends CommonOptions {
 	/**
 	 * The list of options to display.
 	 */
-	options: TOption[];
+	options: readonly TOption[];
 
 	/**
 	 * The index of the currently active/selected option.

packages/prompts/src/multi-select.ts

@@ -23,8 +23,8 @@ export const MULTISELECT_INSTRUCTIONS = [
 
 export interface MultiSelectOptions<Value> extends CommonOptions {
 	message: string;
-	options: Option<Value>[];
-	initialValues?: Value[];
+	options: readonly Option<Value>[];
+	initialValues?: readonly Value[];
 	maxItems?: number;
 	required?: boolean;
 	cursorAt?: Value;

packages/prompts/test/multi-select.test.ts

@@ -1,4 +1,14 @@
-import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, test, vi } from 'vitest';
+import {
+	afterAll,
+	afterEach,
+	beforeAll,
+	beforeEach,
+	describe,
+	expect,
+	expectTypeOf,
+	test,
+	vi,
+} from 'vitest';
 import * as prompts from '../src/index.js';
 import { MockReadable, MockWritable } from './test-utils.js';
 
@@ -492,4 +502,28 @@ describe.each(['true', 'false'])('multiselect (isCI = %s)', (isCI) => {
 		await result;
 		expect(output.buffer).toMatchSnapshot();
 	});
+
+	test('accepts readonly options defined with `as const`', async () => {
+		const options = [
+			{ value: 'opt0', label: 'Option 0' },
+			{ value: 'opt1', label: 'Option 1' },
+		] as const;
+
+		const result = prompts.multiselect({
+			message: 'foo',
+			options,
+			initialValues: ['opt1'] as const,
+			input,
+			output,
+		});
+
+		input.emit('keypress', '', { name: 'space' });
+		input.emit('keypress', '', { name: 'return' });
+
+		const value = await result;
+
+		expect(prompts.isCancel(value)).toBe(false);
+		expect(value).toEqual(['opt1', 'opt0']);
+		expectTypeOf(value).toEqualTypeOf<('opt0' | 'opt1')[] | typeof prompts.CANCEL_SYMBOL>();
+	});
 });